The document discusses secondary storage devices. It provides learning objectives about secondary storage devices, their classification, differences between sequential and direct access storage, and operation of popular devices like magnetic tapes, disks, and optical disks. Specific topics covered include limitations of primary storage, definitions of secondary storage, sequential vs direct access devices, magnetic tape organization, storage capacity and transfer rates, tape drives and controllers, and examples of different tape formats.
The document discusses various input and output devices used in computer systems. It begins by defining input/output devices and their roles in facilitating communication between computers and the external world. It then describes several commonly used input devices such as keyboards, pointing devices, scanners, and microphones for speech recognition. The document provides examples and diagrams to illustrate how these devices function. It aims to help readers understand the basic concepts and purposes of the different I/O devices used in computer systems.
The document discusses the memory system in computers including main memory, cache memory, and different types of memory chips. It provides details on the following key points in 3 sentences:
The document discusses the different levels of memory hierarchy including main memory, cache memory, and auxiliary memory. It describes the basic concepts of memory including addressing schemes, memory access time, and memory cycle time. Examples of different types of memory chips are discussed such as SRAM, DRAM, ROM, and cache memory organization and mapping techniques.
The input unit accepts data and instructions from external devices and converts them to a binary format understood by the computer. Common input devices include the keyboard, mouse, joystick, scanner, microphone, and touchscreen. The output unit converts the computer's binary output to a human readable format and presents it via output devices such as monitors, printers, speakers, projectors, and plotters. The processor, or CPU, fetches instructions from memory, decodes and executes them, and writes results back to memory in four steps: fetch, decode, execute, and write back. It controls the overall functioning of the computer.
The document discusses the Linux kernel buffer cache. It describes the structure of buffer headers and the buffer pool. It outlines 5 scenarios for retrieving a buffer, including if the block is found in the hash queue, a free buffer is available, or if a delayed write buffer needs to be written first. It also covers reading and writing blocks to disk using functions like bread(), breada(), bwrite(), and brelse(). The advantages of the buffer cache in reducing disk access and ensuring integrity are presented.
The document discusses the history and evolution of computers from the 17th century to present day. It covers the development of early calculating machines, Charles Babbage's analytical engine which laid the foundations for modern computers, and the first general purpose electronic computers developed in the 1940s-1950s. The document then describes the five generations of computers, highlighting the key hardware technologies, software technologies, and representative computer systems for each generation from first to second generation machines.
The document provides an overview of the main components of a computer motherboard and how they work together. It discusses the motherboard, CPU, RAM, ROM, expansion slots and boot process. The motherboard holds the processor, memory chips, input/output chips and expansion slots. It connects the components and allows them to communicate via a data bus. The CPU executes instructions from RAM and uses RAM for data processing. Expansion slots allow additional peripherals to connect to the motherboard. The boot process starts the computer and loads the operating system.
Cache memory is a small amount of fast SRAM located between the CPU and main memory that stores frequently accessed data. When the CPU requests data, the cache memory is checked first and if the data is present it can be accessed much faster than main memory. If the data is not in cache memory, it is retrieved from main memory which is slower but larger DRAM. Modern processors use a multi-level cache system with multiple cache levels (L1, L2, etc.) checked sequentially to improve performance.
The document discusses the concept of virtual memory. Virtual memory allows a program to access more memory than what is physically available in RAM by storing unused portions of the program on disk. When a program requests data that is not currently in RAM, it triggers a page fault that causes the needed page to be swapped from disk into RAM. This allows the illusion of more memory than physically available through swapping pages between RAM and disk as needed by the program during execution.
The document discusses various input and output devices used in computer systems. It begins by defining input/output devices and their roles in facilitating communication between computers and the external world. It then describes several commonly used input devices such as keyboards, pointing devices, scanners, and microphones for speech recognition. The document provides examples and diagrams to illustrate how these devices function. It aims to help readers understand the basic concepts and purposes of the different I/O devices used in computer systems.
The document discusses the memory system in computers including main memory, cache memory, and different types of memory chips. It provides details on the following key points in 3 sentences:
The document discusses the different levels of memory hierarchy including main memory, cache memory, and auxiliary memory. It describes the basic concepts of memory including addressing schemes, memory access time, and memory cycle time. Examples of different types of memory chips are discussed such as SRAM, DRAM, ROM, and cache memory organization and mapping techniques.
The input unit accepts data and instructions from external devices and converts them to a binary format understood by the computer. Common input devices include the keyboard, mouse, joystick, scanner, microphone, and touchscreen. The output unit converts the computer's binary output to a human readable format and presents it via output devices such as monitors, printers, speakers, projectors, and plotters. The processor, or CPU, fetches instructions from memory, decodes and executes them, and writes results back to memory in four steps: fetch, decode, execute, and write back. It controls the overall functioning of the computer.
The document discusses the Linux kernel buffer cache. It describes the structure of buffer headers and the buffer pool. It outlines 5 scenarios for retrieving a buffer, including if the block is found in the hash queue, a free buffer is available, or if a delayed write buffer needs to be written first. It also covers reading and writing blocks to disk using functions like bread(), breada(), bwrite(), and brelse(). The advantages of the buffer cache in reducing disk access and ensuring integrity are presented.
The document discusses the history and evolution of computers from the 17th century to present day. It covers the development of early calculating machines, Charles Babbage's analytical engine which laid the foundations for modern computers, and the first general purpose electronic computers developed in the 1940s-1950s. The document then describes the five generations of computers, highlighting the key hardware technologies, software technologies, and representative computer systems for each generation from first to second generation machines.
The document provides an overview of the main components of a computer motherboard and how they work together. It discusses the motherboard, CPU, RAM, ROM, expansion slots and boot process. The motherboard holds the processor, memory chips, input/output chips and expansion slots. It connects the components and allows them to communicate via a data bus. The CPU executes instructions from RAM and uses RAM for data processing. Expansion slots allow additional peripherals to connect to the motherboard. The boot process starts the computer and loads the operating system.
Cache memory is a small amount of fast SRAM located between the CPU and main memory that stores frequently accessed data. When the CPU requests data, the cache memory is checked first and if the data is present it can be accessed much faster than main memory. If the data is not in cache memory, it is retrieved from main memory which is slower but larger DRAM. Modern processors use a multi-level cache system with multiple cache levels (L1, L2, etc.) checked sequentially to improve performance.
The document discusses the concept of virtual memory. Virtual memory allows a program to access more memory than what is physically available in RAM by storing unused portions of the program on disk. When a program requests data that is not currently in RAM, it triggers a page fault that causes the needed page to be swapped from disk into RAM. This allows the illusion of more memory than physically available through swapping pages between RAM and disk as needed by the program during execution.
The document provides information about hard disk drives, including:
- Hard disk drives store digitally encoded data on rapidly rotating platters with magnetic surfaces. Data is stored as binary 0s and 1s.
- Disk structures include tracks, sectors, cylinders, and clusters. Tracks are circular areas on disks, sectors are the smallest storage units, cylinders group same tracks, and clusters are groups of sectors.
- Performance is measured by latency, data rate, and seek time. Latency depends on rotation speed, data rate is bytes/second, and seek time is retrieving requested data.
- Common interfaces are IDE, SATA, and SCSI, which have different connectors and data transfer speeds.
The document discusses the memory hierarchy in computers. It explains that memory is organized in a hierarchy with different levels providing varying degrees of speed and capacity. The levels from fastest to slowest are: registers, cache, main memory, and auxiliary memory such as magnetic disks and tapes. Cache memory sits between the CPU and main memory to bridge the speed gap. It exploits locality of reference to improve memory access speed. The document provides details on the working of each memory level and how they interact with each other.
This document provides an overview of operating systems and some key concepts:
- An operating system manages computer resources and provides an interface between users and hardware. Its main functions include process management, memory management, file management, and security.
- Multiprogramming allows interleaved execution of multiple processes by using memory partitions and context switching between processes. Process states include ready, running, blocked, and completed.
- Memory management involves allocating and deallocating memory to processes as needed. Early systems used fixed-sized memory partitions while more advanced systems use variable partitions that dynamically change in size and location.
Disk Structure (Magnetic)
Disk Attachment
Disk Scheduling Algorithms
FCFS, SSTF, SCAN, LOOK
Disk Management
Formatting, booting, bad sectors
Swap-Space Management
Performance optimization
The History and Generation of ComputersShayan Amir
The document discusses the five generations of computers from the first to fifth generation. It describes the key characteristics of each generation as computers evolved from using vacuum tubes in the first generation to integrated circuits in the third generation to microprocessors in the fourth generation. The goal of the proposed fifth generation is to develop devices with artificial intelligence that can understand natural language and have learning capabilities.
Direct access storage devices (DASDs) include magnetic disks, optical storage devices, and flash memory. Magnetic disks can be fixed-head or movable-head. Movable-head disks use a disk pack of stacked platters and read/write heads that move together to access data located in cylinders. Optical storage uses lasers to read microscopic pits on disks like CDs, DVDs, and Blu-ray discs, allowing more data storage than magnetic disks. Flash memory uses transistors to store data in blocks that must be erased before being rewritten.
Virtual memory is a memory management technique that allows programs to access memory addresses beyond their actual physical RAM size. It maps virtual addresses to physical addresses stored in RAM or on a hard disk using page tables and a translation process. When a program requests a page not in RAM, a page fault occurs and the OS moves a page from disk to RAM, suspending the program until the page is loaded. Page replacement algorithms like LRU then select pages to remove from RAM and write to disk when RAM is full to make space for new pages. This allows for larger memory sizes, more efficient memory usage, and multitasking.
Rajnikant Bal presented a technical seminar report on flash memory. Flash memory is a type of non-volatile solid state memory that can be electrically erased and reprogrammed. It provides benefits over traditional hard drives by being compact, lightweight, and energy efficient. Flash memory is widely used in devices such as digital cameras, smartphones, and MP3 players due to these advantages. The seminar covered the basic workings of flash memory cells, how erase and write operations are performed, and various applications of flash memory technology.
The document discusses various CPU scheduling algorithms including first come first served, shortest job first, priority, and round robin. It describes the basic concepts of CPU scheduling and criteria for evaluating algorithms. Implementation details are provided for shortest job first, priority, and round robin scheduling in C++.
This document provides an overview of mass storage structures and operating system services for mass storage. It discusses disk structure, disk scheduling algorithms, swap space management, RAID structures, and stable storage implementation. The document also describes the physical structure of secondary and tertiary storage devices and their performance characteristics.
The document compares AMD and Intel processors. It finds that AMD processors are generally cheaper than Intel, with a custom-built AMD PC costing $272.92 compared to $484.90 for Intel. While Intel is better for business and research needs, AMD supports a wider range of uses including gaming, video/audio editing, and movies. AMD also offers better graphics and gaming performance due to its 3D Now! technology and runs programs like 3D Studio Max and Photoshop faster than Intel. However, older AMD processors can overheat quicker than Intel.
(Ref : Computer System Architecture by Morris Mano 3rd edition) : Microprogrammed Control unit, micro instructions, micro operations, symbolic and binary microprogram.
Introduction, Memory Hierarchy, Random Access Memory (RAM), Types of RAM, Read Only Memory (ROM), Types of ROM. Introduction, Classification of Secondary Storage Devices, Magnetic Tape, Magnetic Disk, Optical Disk, Magneto Optical disk.
The document discusses virtual memory, including its needs, importance, advantages, and disadvantages. Virtual memory allows a computer to use more memory for programs than is physically installed by storing unused portions on disk. This allows processes to exceed physical memory limits. Page replacement algorithms like FIFO, LRU, and OPT are used to determine which pages to swap in and out between memory and disk.
This presentation discusses different types of storage devices. It begins by introducing storage capacity and properties of storage units like access time and cost. The main types covered are optical storage devices like CDs, DVDs, and Blu-Ray discs which can store large amounts of data but are fragile. Magnetic storage devices discussed are floppy disks with small capacity and hard disks which are the primary computer storage. Solid state flash memory and memory sticks are also covered as portable options.
1) A bit is the smallest unit of computer data and can have a value of 0 or 1. 8 bits form a byte.
2) Common units of computer data storage are the kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB), petabyte (PB), exabyte (EB), zettabyte (ZB), and yottabyte (YB), with each being 1024 times larger than the previous unit.
3) These units are used to measure and describe computer memory, storage, and data transmission speeds in bytes, kilobytes, megabytes etc. depending on the size of the data or storage being referred to
The document discusses different number systems including binary, decimal, octal and hexadecimal. It provides examples of how to represent numbers in these systems and convert between them. The key methods covered are using place values to convert between bases and a division-remainder approach to change from decimal to another base. The goal is to understand how computers use binary numbering and how to work with different bases.
This document discusses the processor and memory components of a computer system. It covers the internal structure of the processor including the central processing unit (CPU) which contains the control unit and arithmetic logic unit. It describes the functions of commonly used registers and factors that determine processor speed. Different types of processors and memory are outlined, including RAM, ROM, and their uses. Memory capacity, organization, and evaluation criteria are also summarized.
The document provides information about hard disk drives, including:
- Hard disk drives store digitally encoded data on rapidly rotating platters with magnetic surfaces. Data is stored as binary 0s and 1s.
- Disk structures include tracks, sectors, cylinders, and clusters. Tracks are circular areas on disks, sectors are the smallest storage units, cylinders group same tracks, and clusters are groups of sectors.
- Performance is measured by latency, data rate, and seek time. Latency depends on rotation speed, data rate is bytes/second, and seek time is retrieving requested data.
- Common interfaces are IDE, SATA, and SCSI, which have different connectors and data transfer speeds.
The document discusses the memory hierarchy in computers. It explains that memory is organized in a hierarchy with different levels providing varying degrees of speed and capacity. The levels from fastest to slowest are: registers, cache, main memory, and auxiliary memory such as magnetic disks and tapes. Cache memory sits between the CPU and main memory to bridge the speed gap. It exploits locality of reference to improve memory access speed. The document provides details on the working of each memory level and how they interact with each other.
This document provides an overview of operating systems and some key concepts:
- An operating system manages computer resources and provides an interface between users and hardware. Its main functions include process management, memory management, file management, and security.
- Multiprogramming allows interleaved execution of multiple processes by using memory partitions and context switching between processes. Process states include ready, running, blocked, and completed.
- Memory management involves allocating and deallocating memory to processes as needed. Early systems used fixed-sized memory partitions while more advanced systems use variable partitions that dynamically change in size and location.
Disk Structure (Magnetic)
Disk Attachment
Disk Scheduling Algorithms
FCFS, SSTF, SCAN, LOOK
Disk Management
Formatting, booting, bad sectors
Swap-Space Management
Performance optimization
The History and Generation of ComputersShayan Amir
The document discusses the five generations of computers from the first to fifth generation. It describes the key characteristics of each generation as computers evolved from using vacuum tubes in the first generation to integrated circuits in the third generation to microprocessors in the fourth generation. The goal of the proposed fifth generation is to develop devices with artificial intelligence that can understand natural language and have learning capabilities.
Direct access storage devices (DASDs) include magnetic disks, optical storage devices, and flash memory. Magnetic disks can be fixed-head or movable-head. Movable-head disks use a disk pack of stacked platters and read/write heads that move together to access data located in cylinders. Optical storage uses lasers to read microscopic pits on disks like CDs, DVDs, and Blu-ray discs, allowing more data storage than magnetic disks. Flash memory uses transistors to store data in blocks that must be erased before being rewritten.
Virtual memory is a memory management technique that allows programs to access memory addresses beyond their actual physical RAM size. It maps virtual addresses to physical addresses stored in RAM or on a hard disk using page tables and a translation process. When a program requests a page not in RAM, a page fault occurs and the OS moves a page from disk to RAM, suspending the program until the page is loaded. Page replacement algorithms like LRU then select pages to remove from RAM and write to disk when RAM is full to make space for new pages. This allows for larger memory sizes, more efficient memory usage, and multitasking.
Rajnikant Bal presented a technical seminar report on flash memory. Flash memory is a type of non-volatile solid state memory that can be electrically erased and reprogrammed. It provides benefits over traditional hard drives by being compact, lightweight, and energy efficient. Flash memory is widely used in devices such as digital cameras, smartphones, and MP3 players due to these advantages. The seminar covered the basic workings of flash memory cells, how erase and write operations are performed, and various applications of flash memory technology.
The document discusses various CPU scheduling algorithms including first come first served, shortest job first, priority, and round robin. It describes the basic concepts of CPU scheduling and criteria for evaluating algorithms. Implementation details are provided for shortest job first, priority, and round robin scheduling in C++.
This document provides an overview of mass storage structures and operating system services for mass storage. It discusses disk structure, disk scheduling algorithms, swap space management, RAID structures, and stable storage implementation. The document also describes the physical structure of secondary and tertiary storage devices and their performance characteristics.
The document compares AMD and Intel processors. It finds that AMD processors are generally cheaper than Intel, with a custom-built AMD PC costing $272.92 compared to $484.90 for Intel. While Intel is better for business and research needs, AMD supports a wider range of uses including gaming, video/audio editing, and movies. AMD also offers better graphics and gaming performance due to its 3D Now! technology and runs programs like 3D Studio Max and Photoshop faster than Intel. However, older AMD processors can overheat quicker than Intel.
(Ref : Computer System Architecture by Morris Mano 3rd edition) : Microprogrammed Control unit, micro instructions, micro operations, symbolic and binary microprogram.
Introduction, Memory Hierarchy, Random Access Memory (RAM), Types of RAM, Read Only Memory (ROM), Types of ROM. Introduction, Classification of Secondary Storage Devices, Magnetic Tape, Magnetic Disk, Optical Disk, Magneto Optical disk.
The document discusses virtual memory, including its needs, importance, advantages, and disadvantages. Virtual memory allows a computer to use more memory for programs than is physically installed by storing unused portions on disk. This allows processes to exceed physical memory limits. Page replacement algorithms like FIFO, LRU, and OPT are used to determine which pages to swap in and out between memory and disk.
This presentation discusses different types of storage devices. It begins by introducing storage capacity and properties of storage units like access time and cost. The main types covered are optical storage devices like CDs, DVDs, and Blu-Ray discs which can store large amounts of data but are fragile. Magnetic storage devices discussed are floppy disks with small capacity and hard disks which are the primary computer storage. Solid state flash memory and memory sticks are also covered as portable options.
1) A bit is the smallest unit of computer data and can have a value of 0 or 1. 8 bits form a byte.
2) Common units of computer data storage are the kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB), petabyte (PB), exabyte (EB), zettabyte (ZB), and yottabyte (YB), with each being 1024 times larger than the previous unit.
3) These units are used to measure and describe computer memory, storage, and data transmission speeds in bytes, kilobytes, megabytes etc. depending on the size of the data or storage being referred to
The document discusses different number systems including binary, decimal, octal and hexadecimal. It provides examples of how to represent numbers in these systems and convert between them. The key methods covered are using place values to convert between bases and a division-remainder approach to change from decimal to another base. The goal is to understand how computers use binary numbering and how to work with different bases.
This document discusses the processor and memory components of a computer system. It covers the internal structure of the processor including the central processing unit (CPU) which contains the control unit and arithmetic logic unit. It describes the functions of commonly used registers and factors that determine processor speed. Different types of processors and memory are outlined, including RAM, ROM, and their uses. Memory capacity, organization, and evaluation criteria are also summarized.
This document discusses the basic organization and functions of a computer system. It describes the five basic operations of inputting, storing, processing, outputting, and controlling. It explains the roles of the main components including the input and output units, storage units, arithmetic logic unit, control unit, and central processing unit. Primary and secondary storage are also defined. The document presents the computer as a system made up of interconnected parts that work together to perform programmed instructions.
The document is the first chapter of a textbook on computer fundamentals. It introduces computers by defining them as electronic devices that can perform high-speed calculations and process data. It describes the characteristics of computers and how they have evolved over several generations from early mechanical calculators and vacuum tube-based machines to today's personal computers, servers and supercomputers. The chapter also outlines the key hardware and software technologies of each generation of computers.
The document discusses multimedia and its components. It defines multimedia as the use of more than one media such as text, graphics, animation, audio, and video to present information. A multimedia computer system requires components like large storage, memory, and display to integrate different media types. Common multimedia applications include presentations, education, games, and virtual reality. The document outlines the key technologies used for each media type and features important for multimedia computers.
This document discusses different types of application software packages. It covers word processing packages, which are used to create, edit, and format documents. Spreadsheet packages allow for numerical analysis and are useful for accounting, budgets, and grading. Graphics packages enable the creation of drawings, pictures, and other visual content. Personal assistance packages help individuals manage schedules, contacts, and finances. The document provides examples and definitions of features for each type of package.
The document discusses different types of computers based on their mode of use. It describes notebook computers, personal computers, workstations, mainframe systems, supercomputers, client and server computers, and handheld computers. For each type, it provides details on their key characteristics, components, uses, and differences between types. The document concludes with a comparison table of the different computer types.
Output devices convert computer signals into movement or actions. They include actuators that receive signals from computers and cause some physical change, like turning a motor or light bulb on or off. Common output devices used with actuators are motors, buzzers, light bulbs, and heaters which are used in appliances and systems to automate functions.
CRT monitors use electron guns to shoot electrons at phosphor particles to display an image, but they are heavy, emit radiation, and cause eye strain. TFT monitors use thin film transistors and liquid crystals to display each pixel and are lighter and cause less eye strain. Laser printers use toner and an electrically charged drum to produce high-quality, fast outputs while inkjet printers produce high-quality color prints but are slower. Dot matrix printers use pins and ink ribbons for noisy, multi-copy printing. Plotters can produce large, high-quality graphics and blueprints using pens or inkjets. Speakers output sound files from computers.
The document discusses various input devices used in computer systems. It describes keyboards, mice, joysticks, touchscreens, scanners, digital cameras and other common input devices. It provides details on how each device works and examples of their uses. Specialized keyboards for ergonomics or disabled users are also mentioned. The document aims to provide a comprehensive overview of the different types of hardware used to input data and instructions into a computer system.
This document discusses different types of secondary storage devices, including magnetic tape, magnetic disks, optical disks, and magneto-optical storage devices. It provides details on the structure, organization, and read/write process of various magnetic storage media like magnetic tapes, floppy disks, hard disks, and zip disks. Magnetic tapes provide inexpensive storage but are sequential access devices. Magnetic disks like hard disks enable direct access and are widely used as primary storage.
The document discusses various input and output devices used in computing systems. It describes 20 different input devices including keyboards, mice, touchscreens, scanners, microphones, and digital cameras. It also explains 14 different output devices like monitors, printers (impact printers like dot matrix and non-impact printers like inkjet and laser), and speakers. The document provides details on the purpose, working mechanism, advantages and disadvantages of each type of input and output device.
Vitamins and minerals are essential nutrients that our bodies need to function properly. This document provides information on key vitamins and minerals, including their uses, food sources, potential deficiencies if intake is inadequate, and consequences of excess intake. It discusses vitamins A, D, E, K, B1, B2, B3, B12, and C and minerals such as sodium, calcium, iodine, iron, phosphorus, fluorine, carbohydrates, fat, and protein.
Magnetic tape consists of a thin plastic ribbon coated with magnetic material that can be magnetized to store binary data in sequential tracks and frames, allowing it to serve as a primary means of backup and data transfer between systems in a cost effective manner. Magnetic tape uses tape heads with electromagnetic coils and ferromagnetic cores to magnetize the coating and read the magnetic patterns representing stored data. While magnetic tape provides high storage capacity at low cost and is suitable for batch processing, it also has disadvantages such as slow data transfer rates and inability to randomly access specific data.
The document discusses key aspects of system implementation and operation including testing and debugging programs, documenting the system, transitioning to the new system, and ongoing system evaluation and maintenance. Specifically, it covers debugging syntax versus logic errors, different types of testing, methods for changeover to a new system, factors considered in system evaluation, and importance of ongoing system maintenance.
The document discusses the Internet and its basic services. It describes how the Internet evolved from ARPANET and initially connected research organizations. It grew rapidly in the late 1980s and now interconnects over 30,000 networks worldwide. The Internet provides services like email, file transfer, telnet, and usenet news. It also discusses the World Wide Web, how web pages use HTML, and how browsers allow users to access and navigate web pages through URLs. Common uses of the Internet mentioned include online communication, software sharing, product promotion, and e-commerce.
The document discusses different types of computers based on their mode of use. It describes notebook computers, personal computers, workstations, mainframe systems, supercomputers, clients and servers, and handheld computers. For each type, it provides details on their typical uses, characteristics, operating systems, vendors, and how they differ from each other.
Secondary storage devices are non-volatile memory that stores large amounts of data at lower costs than primary memory. There are two main types of secondary storage devices: sequential access devices like magnetic tapes that are very fast for sequential data but slow for random access, and direct access storage devices (DASDs) like hard disks that allow for high-capacity random access storage. Magnetic disks are the most widely used secondary storage, offering high storage capacity, reliability, and the ability to directly access stored data.
The document discusses the benefits of meditation for reducing stress and anxiety. Regular meditation practice can help calm the mind and body by lowering heart rate and blood pressure. Studies have shown that meditating for just 10-20 minutes per day can have significant positive impacts on both mental and physical health over time.
The document discusses different types of computer software. It defines software and describes the relationship between software and hardware. There are two major types of software: system software, which controls computer operations, and application software, which performs specific tasks. The document outlines how software is developed and acquired, including buying pre-written software, customizing software, and downloading public domain software. It also discusses firmware, middleware, and the steps involved in software development.
The document discusses secondary storage devices and their classification. It covers magnetic tape, including half-inch tape reels, half-inch tape cartridges, and quarter-inch streamer tape. Magnetic tape uses sequential access and stores data on magnetic tape through read/write heads. Data is organized into files, blocks, and records with markers separating structures on the tape. Magnetic tape capacity and transfer rates depend on recording density and tape speed.
The document discusses secondary storage devices and focuses on magnetic tape. It defines secondary storage and its advantages over primary storage. It classifies common secondary storage devices as sequential or direct access. The document then describes the basic components, storage organization, capacity, transfer rate, and operation of magnetic tapes. Magnetic tape is presented as a sequential access storage device that stores data in the form of magnetic spots on a tape ribbon.
The document discusses secondary storage devices and focuses on magnetic tape. It defines secondary storage and its advantages over primary storage. It classifies common secondary storage devices as sequential or direct access. The document then describes the basic components, storage organization, capacity, transfer rate, and operation of magnetic tapes. Magnetic tape is presented as a sequential access storage device that stores data in the form of magnetic spots on a tape ribbon.
This document discusses secondary storage devices and focuses on magnetic tape. It defines secondary storage and explains how it overcomes limitations of primary storage. Magnetic tape is described as a sequential-access storage device. Key concepts about magnetic tape are explained, including storage organization using frames, tracks and blocking of records. The document also covers magnetic tape storage capacity and data transfer rate. It describes how a tape drive reads and writes data to magnetic tape and is controlled by a tape controller.
The document discusses secondary storage devices and their advantages over primary storage. It covers different types of magnetic tape storage, including half-inch tape reels, half-inch tape cartridges, and quarter-inch streamer tape. The key details covered include tape organization, storage capacity, data transfer rates, tape drives, and tape controllers. Magnetic tape is described as a commonly used sequential-access storage device.
The document is the first chapter of a textbook on computer fundamentals. It introduces computers by defining them as electronic devices that can perform high-speed calculations and process data. It describes the characteristics of computers and how they have evolved over several generations from early mechanical calculators and vacuum tube-based machines to today's integrated circuit-based devices. The chapter also outlines the key hardware and software technologies of each generation of computers.
The document discusses the internal structure and components of a computer's processor and memory. It describes the central processing unit (CPU) as having two main components - the control unit and arithmetic logic unit. The CPU contains registers for storing instructions and data temporarily during processing. Memory is classified as either volatile random access memory (RAM) or non-volatile read-only memory (ROM). Caches provide extremely fast temporary storage between the CPU and main memory to minimize processing speed differences. Different types of processors, memory technologies, and capacities are also outlined.
The document discusses the processor and memory architecture of a computer system. It covers the internal structure of the processor including the central processing unit (CPU), control unit, arithmetic logic unit, registers, and instruction set. It also discusses main memory, different types of processors like RISC, CISC, EPIC and multi-core, and memory concepts like word length, organization, and types of fixed and variable word-length memory. The goal is to explain the key components and concepts related to how the processor and memory work together in a computer system.
The document discusses the processor, memory, and their basic architecture in a computer system. It covers the internal structure of the processor including the central processing unit (CPU) and its two components - the control unit and arithmetic logic unit. It describes the main memory, different types of processors like RISC, CISC, EPIC and multi-core, and characteristics of the memory like volatile nature, random access, and organization. Types of registers and factors affecting processor speed are also summarized.
The document discusses the internal structure of processors and different types of memory. It covers topics like the central processing unit (CPU) which consists of a control unit and arithmetic logic unit. It describes the basic architecture of a computer system including registers, cache memory, and main memory. It also discusses characteristics of different processor types like RISC, CISC, multi-core and different memory types including RAM, ROM, and their variations.
The document discusses the processor, memory, and their basic architecture in a computer system. It covers the internal structure of the processor including the central processing unit (CPU) and its two components - the control unit and arithmetic logic unit. It describes the main memory, different types of processors like RISC, CISC, EPIC and multi-core, and characteristics of the memory like volatile nature, random access, and organization. Types of registers and factors affecting processor speed are also summarized.
The document discusses the history and evolution of computers from the earliest mechanical adding machines through five generations of computers. It describes key characteristics of each generation including representative systems, software technologies, and hardware technologies. The first generation used vacuum tubes, the second used transistors, and subsequent generations used integrated circuits that increased in complexity from SSI to VLSI and ULSI. Each generation brought faster, smaller, more reliable and powerful computers.
The document provides an overview of computer fundamentals and the evolution of computers through different generations. It discusses how computers can perform high-speed calculations and process data. The key characteristics of computers are described such as their automatic, speedy, accurate, and versatile nature. The evolution of early mechanical calculators and computers is summarized, followed by the defining features of the five generations of computers including the technologies and applications that emerged with each generation from the 1940s to the present.
Chapter 01 introduction to computers computingUmair falak
The document provides an overview of computer fundamentals and the evolution of computers through different generations. It discusses how computers can perform high-speed calculations and process data. The key characteristics of computers are described such as their automatic, speedy, accurate, and versatile nature. The evolution of early mechanical calculators and computers is summarized, followed by the defining features of the five generations of computers including the technologies and applications that emerged with each generation from the 1940s to the present.
The document provides an overview of computer fundamentals and the evolution of computers through different generations. It discusses how computers evolved from early mechanical calculators and machines to the present day systems. The key characteristics of computers like speed, accuracy, versatility are explained. The major milestones in computer development are highlighted along with the representative systems, technologies and applications of each generation from first to fifth generation computers.
The document provides an overview of computer fundamentals and the evolution of computers through different generations. It discusses how computers can perform high-speed calculations and process data. The key characteristics of computers are described such as their automatic, speedy, accurate, and versatile nature. The evolution of early mechanical calculators and computers is summarized, followed by the defining features of the five generations of computers including the technologies and applications that emerged with each generation from the 1940s to the present.
The document provides an overview of computer fundamentals and the evolution of computers through different generations:
- It defines a computer as an electronic device that can perform high-speed calculations and process data. Computers have characteristics like speed, accuracy, versatility, and ability to store and recall large amounts of information.
- Early computers were large, expensive, and unreliable. Advances in transistor and integrated circuit technologies led to smaller, more powerful computers through successive generations from vacuum tubes to microprocessors. Modern computers range from portable devices to powerful supercomputers.
computer_fundamentals by sinha & sinha.pdfSarthakGoel39
The document discusses the basic organization and operations of a computer system. It covers the five basic operations of inputting, storing, processing, outputting, and controlling. It describes the main components of a computer system including the input and output units, storage unit, arithmetic logic unit, control unit, and central processing unit. It also provides an overview of computer generations and the evolution of computers from the first generation using vacuum tubes to the modern fifth generation using microprocessors and integrated circuits.
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This document outlines the key concepts covered in Chapter 1 of the book "Computer Fundamentals: Pradeep K. Sinha & Priti Sinha". The chapter introduces computers, defining them as electronic devices that can perform high-speed calculations and process data by storing, manipulating and outputting information. It discusses the evolution of computers from early mechanical calculators to modern electronic digital computers through five generations of technology. Finally, it describes the characteristic features of computers like their automatic, fast, accurate and versatile nature for processing large amounts of stored data.
Similar to Computer Fundamentals Chapter 08 secondary storage (20)
This document describes a proposed nanoscale medical robot, or nanorobot, that could be used as a miniature surgeon inside the human body. It would be introduced via the femoral artery and propelled through the circulatory system. Onboard sensors would help it locate unwanted tissue like tumors or blood clots. It could then destroy this tissue using techniques like resonant microwaves, heat, or physical trauma, without releasing harmful substances. The nanorobot's small size allows it to access and treat problems otherwise inaccessible to normal medical procedures. It has the potential to provide cures for various ailments by operating at the cellular level inside the body.
This document describes a proposed nanoscale medical robot, or nanorobot, that could be used as a miniature surgeon inside the human body. It would be introduced through the femoral artery and propelled through the circulatory system. Onboard sensors would help it locate unwanted tissue like tumors or blood clots. It could then destroy this tissue using techniques like resonant microwaves, heat, or physical trauma, without releasing harmful substances. The nanorobot's small size allows it to access and treat problems otherwise inaccessible to normal medical procedures. It has the potential to cure or control many ailments by operating at the molecular level inside the body.
The document discusses the history and importance of chocolate in human civilization. It notes that chocolate originated in Mesoamerica over 3000 years ago and was prized by the Aztecs and Mayans for its taste. Cocoa beans were used as currency and their cultivation was tightly regulated. The Spanish brought cocoa to Europe in the 16th century, starting its global spread and the development of the chocolate industry.
Here are the key responsibilities:
- Project manager plans and oversees entire project.
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The document discusses business data processing and databases. It defines data and information, and explains how data processing converts raw data into useful information. It then describes the data storage hierarchy and common methods for organizing data, such as the file-oriented and database-oriented approaches. Finally, it discusses database models and management systems.
The document discusses computer languages and programming. It describes three categories of programming languages: machine languages, assembly languages, and high-level languages. It also discusses common programming language tools like assemblers, compilers, linkers, and interpreters. Popular programming languages like FORTRAN, COBOL, BASIC, Pascal, C, C++, C#, Java, RPG, LISP and SNOBOL are also mentioned. The key characteristics and uses of machine languages, assembly languages, high-level languages, compilers, linkers and interpreters are summarized.
The document discusses planning computer programs through algorithms, flowcharts, and pseudocode. It provides examples of algorithms to calculate the number of students who passed with first division and to calculate total bonus amounts for employees. It also describes how algorithms can be represented as programs, flowcharts, or pseudocode. Flowcharts use standardized symbols connected by arrows to show the sequence of instructions, and examples of decision symbols are shown. Finally, an example problem is provided to draw a flowchart to calculate and print a student's percentage marks based on input data.
The document appears to be a series of blank lines with no discernible text or information. In 3 sentences or less, there is no meaningful content that can be summarized from the given document. The document does not contain any words, phrases, or ideas that could be briefly summarized.
The document discusses various topics relating to software project management including:
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2. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Learning Objectives
In this chapter you will learn about:
§ Secondary storage devices and their need
§ Classification of commonly used secondary storage
devices
§ Difference between sequential and direct access
storage devices
§ Basic principles of operation, types, and uses of
popular secondary storage devices such as magnetic
tape, magnetic disk, and optical disk
(Continued on next slide)
Ref Page 117 Chapter 8: Secondary Storage Devices Slide 2/98
3. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Learning Objectives
(Continued from previous slide..)
§ Commonly used mass storage devices
§ Introduction to other related concepts such as RAID,
Jukebox, storage hierarchy, etc.
Ref Page 117 Chapter 8: Secondary Storage Devices Slide 3/98
4. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Limitations of Primary Storage
§ Limited capacity because the cost per bit of storage
is high
§ Volatile - data stored in it is lost when the electric
power is turned off or interrupted
Ref Page 117 Chapter 8: Secondary Storage Devices Slide 4/98
5. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Secondary Storage
§ Used in a computer system to overcome the limitations
of primary storage
§ Has virtually unlimited capacity because the cost per bit
of storage is very low
§ Has an operating speed far slower than that of the
primary storage
§ Used to store large volumes of data on a permanent
basis
§ Also known as auxiliary memory
Ref Page 117 Chapter 8: Secondary Storage Devices Slide 5/98
6. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Classification of Commonly Used Secondary
Storage Devices
Secondary Storage
Devices
Sequential Access Direct Access Devices
Device
Magnetic Tape
Magnetic Optical Disks Memory Storage
Disks Devices
Flash Memory
Floppy Hard CD-ROM Card
WORM CD-RW DVD Drive
Disk Disks
(CD-R)
Zip Disk Disk Pack Winchester Disk
Ref Page 118 Chapter 8: Secondary Storage Devices Slide 6/98
7. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Sequential-access Storage Devices
§ Arrival at the desired storage location may be preceded
by sequencing through other locations
§ Data can only be retrieved in the same sequence in which
it is stored
§ Access time varies according to the storage location of
the information being accessed
§ Suitable for sequential processing applications where
most, if not all, of the data records need to be processed
one after another
§ Magnetic tape is a typical example of such a storage
device
Ref Page 118 Chapter 8: Secondary Storage Devices Slide 7/98
8. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Direct-access Storage Devices
§ Devices where any storage location may be selected
and accessed at random
§ Permits access to individual information in a more
direct or immediate manner
§ Approximately equal access time is required for
accessing information from any storage location
§ Suitable for direct processing applications such as on-
line ticket booking systems, on-line banking systems
§ Magnetic, optical, and magneto-optical disks are
typical examples of such a storage device
Ref Page 118 Chapter 8: Secondary Storage Devices Slide 8/98
9. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape Basics
§ Commonly used sequential-access secondary storage
device
§ Physically, the tape medium is a plastic ribbon, which
is usually ½ inch or ¼ inch wide and 50 to 2400 feet
long
§ Plastic ribbon is coated with a magnetizable recording
material such as iron-oxide or chromium dioxide
§ Data are recorded on the tape in the form of tiny
invisible magnetized and non-magnetized spots
(representing 1s and 0s) on its coated surface
§ Tape ribbon is stored in reels or a small cartridge or
cassette
Ref Page 119 Chapter 8: Secondary Storage Devices Slide 9/98
10. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape - Storage Organization
(Example 1)
A frame Characters for
Track/Channel
numbers corresponding codes
0 12 3 4 5 6 7 8 9 A B C D E F G
Parity bit 7
6 Each vertical
Zone
line represents
5
a binary 1 bit
4
Numeric 3
2
1
Illustrates the concepts of frames, tracks, parity bit, and character-by-character data
storage
Ref Page 119 Chapter 8: Secondary Storage Devices Slide 10/98
11. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape - Storage Organization (Example 2)
Track/ channel Characters for
numbers A frame for each corresponding codes
character
0 1 2 3 4 5 6 7 8 9 A B Each vertical
8’s digit line represents
9
a binary
Track 2’s digit 8
1 bit
representation Added zone 7
Added zone 6
Zone 5
Parity bit 4
Zone 3
Unit’s digit 2
4’s digit 1
Illustrates the concepts of frames, tracks, parity bit, and character-by-character data
storage
Ref Page 120 Chapter 8: Secondary Storage Devices Slide 11/98
12. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape - Storage Organization (Example 3)
Tape motion
IBG R1 IBG R2 IBG R3 IBG R4 IBG R5 IBG R6
(a) An unblocked tape. There is an IBG after each record.
Tape motion
IBG R1 R2 IBG R3 R4 IBG R5 R6 IBG R7 R8 IBG
(b) A tape which uses a blocking factor of two. There is an IBG after every two records.
Tape motion
IBG R1 R2 R3 IBG R4 R5 R6 IBG R7 R8 R9 IBG
(c) A tape which uses a blocking factor of three. There is an IBG after every three records.
Illustrates the concepts of blocking of records, inter-block gap (IBG), and blocking factor
Ref Page 120 Chapter 8: Secondary Storage Devices Slide 12/98
13. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape - Storage Organization (Example 4)
File header
File header File trailer label of next
label label file
Tape motion
Block of Block of
IBG IBG IBG IBG
records records
Illustrates the concepts of multiple blocks of records forming a file that is
separated from other files by a file header label in the beginning and a file trailer
label at the end of the file
Ref Page 120 Chapter 8: Secondary Storage Devices Slide 13/98
14. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape-Storage Organization (Example 5)
Tape header
label File trailer
label of
BOT File header File trailer
label last file
marker label
unused IBG IB Blocks of records of IBG IBG IB unused
the file separated by
tape G G tape
IBGs
Tape motion
EOT marker
Illustrates the concepts of Beginning of Tape (BoT) and End of Tape
(EoT) markers, and tape header label
Ref Page 120 Chapter 8: Secondary Storage Devices Slide 14/98
15. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape Storage Capacity
§ Storage capacity of a tape =
Data recording density x Length
§ Data recording density is the amount of data that can be
stored on a given length of tape. It is measured in bytes
per inch (bpi)
§ Tape density varies from 800 bpi in older systems to
77,000 bpi in some of the modern systems
§ Actual storage capacity of a tape may be anywhere from
35% to 70% of its total storage capacity, depending on
the storage organization used
Ref Page 120 Chapter 8: Secondary Storage Devices Slide 15/98
16. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape – Data Transfer Rate
§ Refers to characters/second that can be transmitted to
the memory from the tape
§ Transfer rate measurement unit is bytes/second (bps)
§ Value depends on the data recording density and the
speed with which the tape travels under the read/write
head
§ A typical value of data transfer rate is 7.7 MB/second
Ref Page 121 Chapter 8: Secondary Storage Devices Slide 16/98
17. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape – Tape Drive
§ Used for writing/reading of data to/from a magnetic
tape ribbon
§ Different for tape reels, cartridges, and cassettes
§ Has read/write heads for reading/writing of data on
tape
§ A magnetic tape reel/cartridge/cassette has to be first
loaded on a tape drive for reading/writing of data on it
§ When processing is complete, the tape is removed
from the tape drive for off-line storage
Ref Page 121 Chapter 8: Secondary Storage Devices Slide 17/98
18. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape – Tape Controller
§ Tape drive is connected to and controlled by a tape
controller that interprets the commands for operating the
tape drive
§ A typical set of commands supported by a tape controller
are:
Read reads one block of data
Write writes one block of data
Write tape header label used to update the contents of tape header label
Erase tape erases the data recorded on a tape
Back space one block rewinds the tape to the beginning of previous block
(Continued on next slide)
Ref Page 121 Chapter 8: Secondary Storage Devices Slide 18/98
19. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Tape – Tape Controller
(Continued from previous slide..)
Forward space one block forwards the tape to the beginning
of next block
Forward space one file forwards the tape to the beginning
of next file
Rewind fully rewinds the tape
Unload releases the tape drive’s grip so
that the tape spool can be
unmountedfrom the tape drive
Ref Page 121 Chapter 8: Secondary Storage Devices Slide 19/98
20. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Types of Magnetic Tape
§ ½-inch tape reel
§ ½-inch tape cartridge
§ ¼-inch streamer tape
§ 4-mm digital audio tape (DAT)
Ref Page 121 Chapter 8: Secondary Storage Devices Slide 20/98
21. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Half-inch Tape Reel
§ Uses ½ inch wide tape ribbon stored on a tape reel
§ Uses parallel representation method of storing data, in
which data are read/written a byte at a time
§ Uses a read/write head assembly that has one
read/write head for each track
§ Commonly used as archival storage for off-line storage
of data and for exchange of data and programs
between organizations
§ Fast getting replaced by tape cartridge, streamer tape,
and digital audio tape they are more compact, cheaper
and easier to handle
Ref Page 122 Chapter 8: Secondary Storage Devices Slide 21/98
23. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Tape Drive of Half-inch Tape Reel
Supply Take-up
reel Magnetic tape reel
Read/write
head assembly
Vacuum
columns
Tape loops
varying in
length
Ref Page 122 Chapter 8: Secondary Storage Devices Slide 23/98
24. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Half-inch Tape Cartridge
§ Uses ½ inch wide tape ribbon sealed in a cartridge
§ Has 36 tracks, as opposed to 9 tracks for most half-inch
tape reels
§ Stores data using parallel representation. Hence, 4 bytes
of data are stored across the width of the tape. This
enables more bytes of data to be stored on the same
length of tape
§ Tape drive reads/writes on the top half of the tape in
one direction and on the bottom half in the other
direction
Ref Page 122 Chapter 8: Secondary Storage Devices Slide 24/98
26. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Quarter-inch Streamer Tape
§ Uses ¼ inch wide tape ribbon sealed in a cartridge
§ Uses serial representation of data recording (data bits
are aligned in a row one after another in tracks)
§ Can have from 4 to 30 tracks, depending on the tape
drive
§ Depending on the tape drive, the read/write head
reads/writes data on one/two/four tracks at a time
§ Eliminates the need for the start/stop operation of
traditional tape drives
(Continued on next slide)
Ref Page 123 Chapter 8: Secondary Storage Devices Slide 26/98
27. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Quarter-inch Streamer Tape
(Continued from previous slide..)
§ Can read/write data more efficiently than the
traditional tape drives because there is no start/stop
mechanism
§ Make more efficient utilization of tape storage area
than traditional tape drives because IBGs are not
needed
§ The standard data formats used in these tapes is
known as the QIC standard
Ref Page 123 Chapter 8: Secondary Storage Devices Slide 27/98
28. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Quarter-inch Streamer Tape (Example)
Recording area Recording area
begins here ends here
Tracks
1 1 0 1 1 0 0 1 1 1 0 1 0.
2 ..
0 0 1 0 1 0 0 1 1 1 0 1...
3 Unused Unused
4 portion portion
of the of the
5 tape tape
6
7
8
Ref Page 123 Chapter 8: Secondary Storage Devices Slide 28/98
29. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
4mm Digital Audio Tape (DAT)
§ Uses 4mm wide tape ribbon sealed in a cartridge
§ Has very high data recording density
§ Uses a tape drive that uses helical scan technique for
data recording, in which two read heads and two write
heads are built into a small wheel
§ DAT drives use a data recording format called Digital
Data Storage (DDS), which provides three levels of
error-correcting code
§ Typical capacity of DAT cartridges varies from
4 GB to 14 GB
Ref Page 123 Chapter 8: Secondary Storage Devices Slide 29/98
30. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
The Helical Scan Techniques
Used in DAT Drives
Write head B
Read head A
Spinning
Read head B
helical
scan
Write head A
Moving tape
Shaft
Ref Page 123 Chapter 8: Secondary Storage Devices Slide 30/98
31. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Advantages of Magnetic Tapes
§ Storage capacity is virtually unlimited because as many
tapes as required can be used for storing very large
data sets
§ Cost per bit of storage is very low for magnetic tapes.
§ Tapes can be erased and reused many times
§ Tape reels and cartridges are compact and light in
weight
§ Easy to handle and store.
§ Very large amount of data can be stored in a small
storage space
(Continued on next slide)
Ref Page 123 Chapter 8: Secondary Storage Devices Slide 31/98
32. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Advantages of Magnetic Tapes
(Continued from previous slide..)
§ Compact size and light weight
§ Magnetic tape reels and cartridges are also easily
portable from one place to another
§ Often used for transferring data and programs from
one computer to another that are not linked together
Ref Page 123 Chapter 8: Secondary Storage Devices Slide 32/98
33. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Limitations of Magnetic Tapes
§ Due to their sequential access nature, they are not
suitable for storage of those data that frequently
require to be accessed randomly
§ Must be stored in a dust-free environment because
specks of dust can cause tape-reading errors
§ Must be stored in an environment with properly
controlled temperature and humidity levels
§ Tape ribbon may get twisted due to warping, resulting
in loss of stored data
§ Should be properly labeled so that some useful data
stored on a particular tape is not erased by mistake
Ref Page 123 Chapter 8: Secondary Storage Devices Slide 33/98
34. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Uses of Magnetic Tapes
§ For applications that are based on sequential data
processing
§ Backing up of data for off-line storage
§ Archiving of infrequently used data
§ Transferring of data from one computer to another that
are not linked together
§ As a distribution media for software by vendors
Ref Page 124 Chapter 8: Secondary Storage Devices Slide 34/98
35. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk - Basics
§ Commonly used direct-access secondary storage device.
§ Physically, a magnetic disk is a thin, circular
plate/platter made of metal or plastic that is usually
coated on both sides with a magnetizable recording
material such as iron-oxide
§ Data are recorded on the disk in the form of tiny
invisible magnetized and non-magnetized spots
(representing 1s and 0s) on the coated surfaces of the
disk
§ The disk is stored in a specially designed protective
envelope or cartridge, or several of them are stacked
together in a sealed, contamination-free container
Ref Page 124 Chapter 8: Secondary Storage Devices Slide 35/98
36. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Storage Organization
Illustrates the Concept of Tracks
200 Track 000
§ A disk’s surface is divided into
Tracks
a number of invisible
concentric circles called tracks
§ The tracks are numbered
consecutively from outermost
to innermost starting from
zero
Track
§ The number of tracks on a
… …
199 disk may be as few as 40 on
small, low-capacity disks, to
several thousand on large,
high-capacity disks
Ref Page 125 Chapter 8: Secondary Storage Devices Slide 36/98
37. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Storage Organization
Illustrates the Concept of Sectors
A sector
§ Each track of a disk is
subdivided into sectors
§ There are 8 or more
sectors per track
§ A sector typically contains
512 bytes
§ Disk drives are designed to
read/write only whole
sectors at a time
Ref Page 125 Chapter 8: Secondary Storage Devices Slide 37/98
38. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Storage Organization
Illustrates Grouping of Tracks and Use of Different
Number of Sectors in Tracks of Different Groups for
Increased Storage Capacity
§ Innermost group of tracks
has 8 sectors/track
§ Next groups of tracks has
9 sectors/track
§ Outermost group of tracks
has 10 sectors/track
Ref Page 125 Chapter 8: Secondary Storage Devices Slide 38/98
39. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Disk Address or
Address of a Record on a Disk
§ Disk address represents the physical location of the
record on the disk
§ It is comprised of the sector number, track number,
and surface number (when double-sided disks are
used)
§ This scheme is called the CHS addressing or Cylinder-
Head-Sector addressing. The same is also referred to
as disk geometry
Ref Page 126 Chapter 8: Secondary Storage Devices Slide 39/98
40. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Storage Organization
(Illustrates the Concept of Cylinder)
Central shaft
Upper surface
not used
Read/Write head
Surface - 0 Direction of
Surface - 1 movement of
access arms
Surface - 2 assembly
Cylinder
Surface - 3
Access arms
Surface - 4
assembly
Surface - 5
Lower surface
not used
No. of disk platters = 4, No. of usable surfaces = 6. A set of corresponding
tracks on all the 6 surfaces is called a cylinder.
Ref Page 127 Chapter 8: Secondary Storage Devices Slide 40/98
41. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Storage Capacity
Storage capacity of a disk system = Number of recording surfaces
× Number of tracks per surface
× Number of sectors per track
× Number of bytes per sector
Ref Page 126 Chapter 8: Secondary Storage Devices Slide 41/98
42. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk Pack – Access Mechanism
One read/write
head per surface Central shaft
Direction of
movement of
access arms
assembly
Access arms
assembly
Vertical cross section of a disk system. There is one read/write head per
recording surface
Ref Page 127 Chapter 8: Secondary Storage Devices Slide 42/98
43. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Access Time
§ Disk access time is the interval between the instant a
computer makes a request for transfer of data from a
disk system to the primary storage and the instant this
operation is completed
§ Disk access time depends on the following three
parameters:
– Seek Time: It is the time required to position the
read/write head over the desired track, as soon as
a read/write command is received by the disk unit
– Latency: It is the time required to spin the desired
sector under the read/write head, once the
read/write head is positioned on the desired track
Ref Page 128 Chapter 8: Secondary Storage Devices Slide 43/98
44. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Access Time
– Transfer Rate: It is the rate at which data are
read/written to the disk, once the read/write head
is positioned over the desired sector
§ As the transfer rate is negligible as compared to seek
time and latency,
Average access time
= Average seek time + Average latency
Ref Page 128 Chapter 8: Secondary Storage Devices Slide 44/98
45. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Disk Formatting
§ Process of preparing a new disk by the computer
system in which the disk is to be used.
§ For this, a new (unformatted) disk is inserted in the disk
drive of the computer system and the disk formatting
command is initiated
§ Low-level disk formatting
§ Disk drive’s read/write head lays down a magnetic
pattern on the disk’s surface
§ Enables the disk drive to organize and store the
data in the data organization defined for the disk
drive of the computer
(Continued on next slide)
Ref Page 129 Chapter 8: Secondary Storage Devices Slide 45/98
46. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Disk Formatting
(Continued from previous slide..)
§ OS-level disk formatting
§ Creates the File Allocation Table (FAT) that is a
table with the sector and track locations of data
§ Leaves sufficient space for FAT to grow
§ Scans and marks bad sectors
§ One of the basic tasks handled by the computer’s
operating system
§ Enables the use of disks manufactured by third party
vendors into one’s own computer system
Ref Page 129 Chapter 8: Secondary Storage Devices Slide 46/98
47. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Disk Drive
§ Unit used for reading/writing of data on/from a
magnetic disk
§ Contains all the mechanical, electrical and
electronic components for holding one or more
disks and for reading or writing of information on
to it
(Continued on next slide)
Ref Page 129 Chapter 8: Secondary Storage Devices Slide 47/98
48. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Disk Drive
(Continued from previous slide..)
§ Although disk drives vary greatly in their shape, size
and disk formatting pattern, they can be broadly
classified into two types:
– Those with interchangeable magnetic disks,
which allow the loading and unloading of
magnetic disks as and when they are needed for
reading/writing of data on to them
– Those with fixed magnetic disks, which come
along with a set of permanently fixed disks. The
disks are not removable from their disk drives
Ref Page 129 Chapter 8: Secondary Storage Devices Slide 48/98
49. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Magnetic Disk – Disk Controller
§ Disk drive is connected to and controlled by a disk
controller, which interprets the commands for
operating the disk drive
§ Typically supports only read and write commands,
which need disk address (surface number,
cylinder/track number, and sector number) as
parameters
§ Connected to and controls more than one disk drive, in
which case the disk drive number is also needed as a
parameters of read and write commands
Ref Page 130 Chapter 8: Secondary Storage Devices Slide 49/98
50. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Types of Magnetic Disks
Magnetic Disks
Floppy Disks Hard Disks
Zip/Bernoulli Disks Disk Packs Winchester
Disks
Ref Page 130 Chapter 8: Secondary Storage Devices Slide 50/98
51. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Floppy Disks
§ Round, flat piece of flexible plastic disks coated with
magnetic oxide
§ So called because they are made of flexible plastic
plates which can bend
§ Also known as floppies or diskettes
§ Plastic disk is encased in a square plastic or vinyl jacket
cover that gives handling protection to the disk surface
(Continued on next slide)
Ref Page 130 Chapter 8: Secondary Storage Devices Slide 51/98
52. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Floppy Disks
(Continued from previous slide..)
§ The two types of floppy disks in use today are:
§ 5¼-inch diskette, whose diameter is 5¼-inch.
It is encased in a square, flexible vinyl jacket
§ 3½-inch diskette, whose diameter is 3½-inch.
It is encased in a square, hard plastic jacket
§ Most popular and inexpensive secondary storage
medium used in small computers
Ref Page 131 Chapter 8: Secondary Storage Devices Slide 52/98
53. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
A 5¼-inch Floppy Disk
User’s label for
Manufacturer’s
identification purpose
label
Write protect notch
Drive spindle
hole in disk
5¼ - inch
Drive access opening
in jacket
Aperture in the jacket
through which the
read/write head makes
direct contact with the
disk surface
5¼ - inch
A 5¼-inch floppy disk enclosed within jacket. The drive mechanism clamps
on to a portion of the disk exposed by the drive access opening in the jacket
Ref Page 131 Chapter 8: Secondary Storage Devices Slide 53/98
54. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
A 3½-inch Floppy Disk
Opening for inserting the
Light indicator disk inside the drive
(blinks when
read/write
operation takes Floppy disk
place) (a) Front view of a floppy disk eject button
drive.
Sliding metal
piece cover
3½” - inch
User’s label for
identification
Write-protect
plastic tab
3½” - inch
(b) A 3½ - inch floppy disk.
Ref Page 131 Chapter 8: Secondary Storage Devices Slide 54/98
55. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Storage Capacities of Various Types of Floppy
Disks
Size No. of Approximate
(Diameter No. of No. of No. of Capacity
surfaces tracks sectors/track bytes/sector in bytes capacity
in inches)
5¼ 2 40 9 512 3,68,640 360 KB
5¼ 2 80 15 512 12,28,800 1.2 MB
3½ 2 40 18 512 7,37,280 720 KB
3½ 2 80 18 512 14,74,560 1.4 MB
3½ 2 80 36 512 29,49,120 2.88 MB
Ref Page 131 Chapter 8: Secondary Storage Devices Slide 55/98
56. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Hard Disks
§ Round, flat piece of rigid metal (frequently aluminium)
disks coated with magnetic oxide
§ Come in many sizes, ranging from 1 to 14-inch
diameter.
§ Depending on how they are packaged, hard disks are of
three types:
§ Zip/Bernoulli disks
§ Disk packs
§ Winchester disks
§ Primary on-line secondary storage device for most
computer systems today
Ref Page 132 Chapter 8: Secondary Storage Devices Slide 56/98
57. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Zip/Bernoulli Disks
§ Uses a single hard disk platter encased in a plastic
cartridge
§ Disk drives may be portable or fixed type
§ Fixed type is part of the computer system, permanently
connected to it
§ Portable type can be carried to a computer system,
connected to it for the duration of use, and then can be
disconnected and taken away when the work is done
§ Zip disks can be easily inserted/removed from a zip drive
just as we insert/remove floppy disks in a floppy disk
drive
Ref Page 132 Chapter 8: Secondary Storage Devices Slide 57/98
58. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Disk Packs
§ Uses multiple (two or more) hard disk platters
mounted on a single central shaft
§ Disk drives have a separate read/write head for each
usable disk surface (the upper surface of the top-most
disk and the lower surface of the bottom most disk is
not used)
§ Disks are of removable/interchangeable type in the
sense that they have to be mounted on the disk drive
before they can be used, and can be removed and
kept off-line when not in use
Ref Page 132 Chapter 8: Secondary Storage Devices Slide 58/98
59. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Winchester Disks
§ Uses multiple (two or more) hard disk platters
mounted on a single central shaft
§ Hard disk platters and the disk drive are sealed
together in a contamination-free container and cannot
be separated from each other
(Continued on next slide)
Ref Page 132 Chapter 8: Secondary Storage Devices Slide 59/98
60. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Winchester Disks
(Continued from previous slide..)
§ For the same number of disks, Winchester disks have
larger storage capacity than disk packs because:
– All the surfaces of all disks are used for data
recording
They employ much greater precision of data recording,
resulting in greater data recording density
§ Named after the .30-30 Winchester rifle because the
early Winchester disk systems had two 30-MB disks
sealed together with the disk drive
Ref Page 132 Chapter 8: Secondary Storage Devices Slide 60/98
61. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Advantages of Magnetic Disks
§ More suitable than magnetic tapes for a wider range of
applications because they support direct access of data
§ Random access property enables them to be used
simultaneously by multiple users as a shared device. A
tape is not suitable for such type of usage due to its
sequential-access property
§ Suitable for both on-line and off-line storage of data
(Continued on next slide)
Ref Page 133 Chapter 8: Secondary Storage Devices Slide 61/98
62. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Advantages of Magnetic Disks
(Continued from previous slide..)
§ Except for the fixed type Winchester disks, the storage
capacity of other magnetic disks is virtually unlimited
as many disks can be used for storing very large data
sets
§ Due to their low cost and high data recording densities,
the cost per bit of storage is low for magnetic disks.
§ An additional cost benefit is that magnetic disks can be
erased and reused many times
§ Floppy disks and zip disks are compact and light in
weight. Hence they are easy to handle and store.
§ Very large amount of data can be stored in a small
storage space
(Continued on next slide)
Ref Page 133 Chapter 8: Secondary Storage Devices Slide 62/98
63. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Advantages of Magnetic Disks
§ Due to their compact size and light weight, floppy disks
and zip disks are also easily portable from one place to
another
§ They are often used for transferring data and programs
from one computer to another, which are not linked
together
§ Any information desired from a disk storage can be
accessed in a few milliseconds because it is a direct
access storage device
(Continued on next slide)
Ref Page 133 Chapter 8: Secondary Storage Devices Slide 63/98
64. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Advantages of Magnetic Disks
(Continued from previous slide..)
§ Data transfer rate for a magnetic disk system is
normally higher than a tape system
§ Magnetic disks are less vulnerable to data corruption
due to careless handling or unfavorable temperature
and humidity conditions than magnetic tapes
Ref Page 133 Chapter 8: Secondary Storage Devices Slide 64/98
65. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Limitations of Magnetic Disks
§ Although used for both random processing and
sequential processing of data, for applications of the
latter type, it may be less efficient than magnetic
tapes
§ More difficult to maintain the security of information
stored on shared, on-line secondary storage devices,
as compared to magnetic tapes or other types of
magnetic disks
(Continued on next slide)
Ref Page 134 Chapter 8: Secondary Storage Devices Slide 65/98
66. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Limitations of Magnetic Disks
(Continued from previous slide..)
§ For Winchester disks, a disk crash or drive failure often
results in loss of entire stored data. It is not easy to
recover the lost data. Suitable backup procedures are
suggested for data stored on Winchester disks
§ Some types of magnetic disks, such as disk packs and
Winchester disks, are not so easily portable like
magnetic tapes
§ On a cost-per-bit basis, the cost of magnetic disks is
low, but the cost of magnetic tapes is even lower
(Continued on next slide)
Ref Page 134 Chapter 8: Secondary Storage Devices Slide 66/98
67. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Limitations of Magnetic Disks
(Continued from previous slide..)
§ Must be stored in a dust-free environment
§ Floppy disks, zip disks and disk packs should be
labeled properly to prevent erasure of useful data by
mistake
Ref Page 134 Chapter 8: Secondary Storage Devices Slide 67/98
68. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Uses of Magnetic Disks
§ For applications that are based on random data
processing
§ As a shared on-line secondary storage device.
Winchester disks and disk packs are often used for
this purpose
§ As a backup device for off-line storage of data. Floppy
disks, zip disks, and disk packs are often used for this
purpose
(Continued on next slide)
Ref Page 134 Chapter 8: Secondary Storage Devices Slide 68/98
69. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Uses of Magnetic Disks
(Continued from previous slide..)
§ Archiving of data not used frequently, but may be
used once in a while. Floppy disks, zip disks, and
disk packs are often used for this purpose
§ Transferring of data and programs from one
computer to another that are not linked together.
Floppy disks and zip disks are often used for this
purpose
§ Distribution of software by vendors. Originally sold
software or software updates are often distributed by
vendors on floppy disks and zip disks
Ref Page 134 Chapter 8: Secondary Storage Devices Slide 69/98
70. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Optical Disk – Basics
§ Consists of a circular disk, which is coated with a thin
metal or some other material that is highly reflective
§ Laser beam technology is used for recording/reading
of data on the disk
§ Also known as laser disk / optical laser disk, due to
the use of laser beam technology
§ Proved to be a promising random access medium for
high capacity secondary storage because it can store
extremely large amounts of data in a limited space
Ref Page 134 Chapter 8: Secondary Storage Devices Slide 70/98
71. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Optical Disk – Storage Organization
§ Has one long spiral track, which starts at the outer edge
and spirals inward to the center
§ Track is divided into equal size sectors
(a) Track pattern on an optical disk (b) Track pattern on a magnetic disk
Difference in track patterns on optical and magnetic disks.
Ref Page 135 Chapter 8: Secondary Storage Devices Slide 71/98
72. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Optical Disk – Storage Capacity
Storage capacity of an optical disk
= Number of sectors
× Number of bytes per sector
The most popular optical disk uses a disk of 5.25 inch
diameter with storage capacity of around 650 Megabytes
Ref Page 135 Chapter 8: Secondary Storage Devices Slide 72/98
73. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Optical Disk – Access Mechanism
Laser Laser
beam beam
source source
Prism Prism
Sensor Sensor
Laser beam gets Laser beam gets
scattered by a pit reflect by a land
(represents 0) (represents1)
Land Land
Pit Land
Pit Pit
Ref Page 136 Chapter 8: Secondary Storage Devices Slide 73/98
74. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Optical Disk – Access Time
§ With optical disks, each sector has the same length
regardless of whether it is located near or away from
the disk’s center
§ Rotation speed of the disk must vary inversely with
the radius. Hence, optical disk drives use a constant
linear velocity (CLV) encoding scheme
§ Leads to slower data access time (larger access time)
for optical disks than magnetic disks
§ Access times for optical disks are typically in the
range of 100 to 300 milliseconds and that of hard
disks are in the range of 10 to 30 milliseconds
Ref Page 137 Chapter 8: Secondary Storage Devices Slide 74/98
75. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Optical Disk Drive
§ Uses laser beam technology for reading/writing of data
§ Has no mechanical read/write access arm
§ Uses a constant linear velocity (CLV) encoding scheme,
in which the rotational speed of the disk varies inversely
with the radius
Ref Page 136 Chapter 8: Secondary Storage Devices Slide 75/98
76. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Optical Disk Drive
Volume control button used
Light
when the drive is used to Optical disk
indicator
play a music CD
A headphone socket Is placed on
enables the user to top of this
plug-in head-phones groove
and listen to recorded Tray eject Direction of
sound when the drive button movement of
is used to play music the tray
CDs. Optical disk tray
Ref Page 137 Chapter 8: Secondary Storage Devices Slide 76/98
77. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Types of Optical Disks
The types of optical disks in use today are:
CD-ROM
§ Stands for Compact Disk-Read Only Memory
§ Packaged as shiny, silver color metal disk of 5¼
inch (12cm) diameter, having a storage capacity of
about 650 Megabytes
§ Disks come pre-recorded and the information
stored on them cannot be altered
§ Pre-stamped (pre-recorded) by their suppliers, by a
process called mastering
(Continued on next slide)
Ref Page 138 Chapter 8: Secondary Storage Devices Slide 77/98
78. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Types of Optical Disks
(Continued from previous slide..)
§ Provide an excellent medium to distribute large
amounts of data in electronic dorm at low cost.
§ A single CD-ROM disk can hold a complete
encyclopedia, or a dictionary, or a world atlas, or
biographies of great people, etc
§ Used for distribution of electronic version of
conference proceedings, journals, magazines,
books, and multimedia applications such as video
games
§ Used by software vendors for distribution of
software to their customers
Ref Page 138 Chapter 8: Secondary Storage Devices Slide 78/98
79. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Types of Optical Disks
WORM Disk / CD-Recordable (CD-R)
§ Stands for Write Once Read Many. Data can be written
only once on them, but can be read many times
§ Same as CD-ROM and has same storage capacity
§ Allow users to create their own CD-ROM disks by using
a CD-recordable (CD-R) drive that can be attached to
a computer as a regular peripheral device
§ Data to be recorded can be written on its surface in
multiple recording sessions
(Continued on next slide)
Ref Page 138 Chapter 8: Secondary Storage Devices Slide 79/98
80. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Types of Optical Disks
(Continued from previous slide..)
§ Sessions after the first one are always additive
and cannot alter the etched/burned information of
earlier sessions
§ Information recorded on them can be read by any
ordinary CD-ROM drive
§ They are used for data archiving and for making a
permanent record of data. For example, many
banks use them for storing their daily transactions
Ref Page 138 Chapter 8: Secondary Storage Devices Slide 80/98
81. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Types of Optical Disks
CD-Read/Write (CD-RW)
§ Same as CD-R and has same storage capacity
§ Allow users to create their own CD-ROM disks by
using a CD-recordable (CD-R) drive that can be
attached to a computer as a regular peripheral
device
§ Data to be recorded can be written on its surface in
multiple recording sessions
§ Made of metallic alloy layer whose chemical
properties are changed during burn and erase
§ Can be erased and written afresh
Ref Page 138 Chapter 8: Secondary Storage Devices Slide 81/98
82. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Types of Optical Disks
Digital Video / Versatile Disk (DVD)
§ Looks same as CD-ROM but has capacity of 4.7 GB or
8.5 GB
§ Designed primarily to store and distribute movies
§ Can be used for storage of large data
§ Allows storage of video in 4:3 or 16:9 aspect-ratios in
MPEG-2 video format using NTSC or PAL resolution
§ Audio is usually Dolby® Digital (AC-3) or Digital
Theater System (DTS) and can be either monaural or
5.1 Surround Sound
Ref Page 138 Chapter 8: Secondary Storage Devices Slide 82/98
83. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Advantages of Optical Disks
§ The cost-per-bit of storage for optical disks is very low
because of their low cost and enormous storage density.
§ The use of a single spiral track makes optical disks an ideal
storage medium for reading large blocks of sequential data,
such as music.
§ Optical disk drives do not have any mechanical read/write
heads to rub against or crash into the disk surface. This
makes optical disks a more reliable storage medium than
magnetic tapes or magnetic disks.
§ Optical disks have a data storage life in excess of 30 years.
This makes them a better storage medium for data
archiving as compared to magnetic tapes or magnetic disks.
Ref Page 139 Chapter 8: Secondary Storage Devices Slide 83/98
84. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Advantages of Optical Disks
§ As data once stored on an optical disk becomes
permanent, danger of stored data getting
inadvertently erased/overwritten is removed
§ Due to their compact size and light weight, optical
disks are easy to handle, store, and port from one
place to another
§ Music CDs can be played on a computer having a CD-
ROM drive along with a sound board and speakers.
This allows computer systems to be also used as
music systems
Ref Page 139 Chapter 8: Secondary Storage Devices Slide 84/98
85. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Limitations of Optical Disks
§ It is largely read-only (permanent) storage medium.
Data once recorded, cannot be erased and hence the
optical disks cannot be reused
§ The data access speed for optical disks is slower than
magnetic disks
§ Optical disks require a complicated drive mechanism
Ref Page 139 Chapter 8: Secondary Storage Devices Slide 85/98
86. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Uses of Optical Disks
§ For distributing large amounts of data at low cost
§ For distribution of electronic version of conference
proceedings, journals, magazines, books, product
catalogs, etc
§ For distribution of new or upgraded versions of
software products by software vendors
(Continued on next slide)
Ref Page 140 Chapter 8: Secondary Storage Devices Slide 86/98
87. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Uses of Optical Disks
(Continued from previous slide..)
§ For storage and distribution of a wide variety of
multimedia applications
§ For archiving of data, which are not used frequently,
but which may be used once in a while
§ WORM disks are often used by end-user companies to
make permanent storage of their own proprietary
information
Ref Page 140 Chapter 8: Secondary Storage Devices Slide 87/98
88. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Memory Storage Devices
Flash Drive (Pen Drive)
§ Relatively new secondary storage device based on
flash memory, enabling easy transport of data from
one computer to another
§ Compact device of the size of a pen, comes in
various shapes and stylish designs and may have
different added features
§ Plug-and-play device that simply plugs into a USB
(Universal Serial Bus) port of a computer, treated as
removable drive
§ Available storage capacities are 8MB, 16MB, 64MB,
128MB, 256MB, 512MB, 1GB, 2GB, 4GB, and 8GB
Ref Page 140 Chapter 8: Secondary Storage Devices Slide 88/98
89. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Memory Storage Devices
Memory Card (SD/MMC)
§ Similar to Flash Drive but in card shape
§ Plug-and-play device that simply plugs into a port
of a computer, treated as removable drive
§ Useful in electronic devices like Camera, music
player
§ Available storage capacities are 8MB, 16MB, 64MB,
128MB, 256MB, 512MB, 1GB, 2GB, 4GB, and 8GB
Ref Page 141 Chapter 8: Secondary Storage Devices Slide 89/98
90. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Mass Storage Devices
§ As the name implies, these are storage systems
having several trillions of bytes of data storage
capacity
§ They use multiple units of a storage media as a single
secondary storage device
§ The three commonly used types are:
1. Disk array, which uses a set of magnetic disks
2. Automated tape library, which uses a set of
magnetic tapes
3. CD-ROM Jukebox, which uses a set of CD-ROMs
§ They are relatively slow having average access times
in seconds
Ref Page 142 Chapter 8: Secondary Storage Devices Slide 90/98
91. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Disk Array
§ Set of hard disks and hard disk drives with a
controller mounted in a single box, forming a single
large storage unit
§ It is commonly known as a RAID (Redundant Array
of Inexpensive Disks)
§ As a secondary storage device, provides enhanced
storage capacity, enhanced performance, and
enhanced reliability
Ref Page 142 Chapter 8: Secondary Storage Devices Slide 91/98
92. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Disk Array
§ Enhanced storage capacity is achieved by using
multiple disks
§ Enhanced performance is achieved by using parallel
data transfer technique from multiple disks
§ Enhanced reliability is achieved by using techniques
such as mirroring or striping
§ In mirroring, the system makes exact copies of files
on two hard disks
§ In striping, a file is partitioned into smaller parts and
different parts of the file are stored on different disks
Ref Page 142 Chapter 8: Secondary Storage Devices Slide 92/98
93. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
A RAID Unit
Multiple
disks
RAID Controller
Computer
Ref Page 142 Chapter 8: Secondary Storage Devices Slide 93/98
94. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Automated Tape Library
§ Set of magnetic tapes and magnetic tape drives with
a controller mounted in a single box, forming a
single large storage unit
§ Large tape library can accommodate up to several
hundred high capacity magnetic tapes bringing the
storage capacity of the storage unit to several
terabytes
§ Typically used for data archiving and as on-line data
backup devices for automated backup in large
computer centers
Ref Page 142 Chapter 8: Secondary Storage Devices Slide 94/98
95. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
CD-ROM Jukebox
§ Set of CD-ROMs and CD-ROM drives with a
controller mounted in a single box, forming a single
large storage unit
§ Large CD-ROM jukebox can accommodate up to
several hundred CD-ROM disks bringing the storage
capacity of the storage unit to several terabytes
§ Used for archiving read-only data in such
applications as on-line museums, on-line digital
libraries, on-line encyclopedia, etc
Ref Page 143 Chapter 8: Secondary Storage Devices Slide 95/98
96. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Storage Hierarchy
As a single type of storage is not superior in speed of access, capacity, and
cost, most computer systems make use of a hierarchy of storage
technologies as shown below.
Smaller capacity, faster Cache Larger capacity,
access time, and higher memory slower access time,
cost per bit stored Main and lower cost per
memory bit stored
On-line, direct-access and
sequential-access secondary
storage device such as hard disk
Off-line, direct-access and sequential-access
secondary storage devices such as magnetic
tape, floppy disk, zip disk, WORM disk, etc.
Mass storage devices such as tape library, CD juke box, etc.
Ref Page 144 Chapter 8: Secondary Storage Devices Slide 96/98
97. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Key Words/Phrases
§ Automated tape library § Floppy disk
§ Auxiliary memory § Hard disk
§ Block § Inter-block gap (IBG)
§ Blocking § Inter-record gap (IRG)
§ Blocking factory § Land
§ CD-ROM § Latency
§ CD-ROM jukebox § Magnetic disk
§ Check bit § Magnetic tape
§ Cylinder § Magnetic tape drive
§ Data transfer rate § Mass storage devices
§ Direct access device § Master file
§ Disk array § Odd parity
§ Disk controller § Off-line storage
§ Disk drive § On-line storage
§ Disk formatting § Optical disk
§ Disk pack § Parallel representation
§ DVD § Parity bit
§ Even parity § Pit
§ File Allocation Tube (FAT)
(Continued on next slide)
Ref Page 144 Chapter 8: Secondary Storage Devices Slide 97/98
98. Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Key Words/Phrases
(Continued from previous slide..)
§ QIC Standard
§ Record
§ Redundant Array of Inexpensive Disks (RAID)
§ Secondary storage
§ Sector
§ Seek time
§ Sequential access device
§ Storage hierarchy
§ Tape controller
§ Track
§ Transaction file
§ Winchester disk
§ WORM disk
§ Zip disk
Ref Page 144 Chapter 8: Secondary Storage Devices Slide 98/98