Memory management is the act of managing computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when no longer needed. This is critical to any advanced computer system where more than a single process might be underway at any time
Memory management is the method by which an operating system handles and allocates primary memory. It tracks the status of memory locations as allocated or free, and determines how memory is distributed among competing processes. Memory can be allocated contiguously or non-contiguously. Contiguous allocation assigns consecutive blocks of memory to a process, while non-contiguous allocation allows a process's memory blocks to be scattered across different areas using techniques like paging or segmentation. Paging divides processes and memory into fixed-size pages and frames to allow non-contiguous allocation while reducing fragmentation.
The document discusses memory management techniques used in operating systems. It describes logical vs physical addresses and how relocation registers map logical addresses to physical addresses. It covers contiguous and non-contiguous storage allocation, including paging and segmentation. Paging divides memory into fixed-size frames and pages, using a page table and translation lookaside buffer (TLB) for address translation. Segmentation divides memory into variable-sized segments based on a program's logical structure. Virtual memory and demand paging are also covered, along with page replacement algorithms like FIFO, LRU and optimal replacement.
This document provides an overview of memory management techniques in operating systems, including both static and dynamic allocation approaches. It discusses fixed and variable partitioning for static allocation, as well as first-fit, next-fit, best-fit, and worst-fit algorithms for dynamic allocation. The document also covers fragmentation, base-limit registers, swapping, paging, and segmentation for virtual memory management. The key aspects of paging include using page tables to map virtual to physical addresses, allowing sharing and abstracting physical organization. Segmentation divides memory into logical segments specified by segment tables.
This presentation describes about the various memory allocation methods like first fit, best fit and worst fit in memory management and also about fragmentation problem and solution for the problem.
This document summarizes and compares paging and segmentation, two common memory management techniques. Paging divides physical memory into fixed-size frames and logical memory into same-sized pages. It maps pages to frames using a page table. Segmentation divides logical memory into variable-sized segments and uses a segment table to map segment numbers to physical addresses. Paging avoids external fragmentation but can cause internal fragmentation, while segmentation avoids internal fragmentation but can cause external fragmentation. Both approaches separate logical and physical address spaces but represent different models of how a process views memory.
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.
This document discusses different memory management techniques used in operating systems. It begins by describing the basic components and functions of memory. It then explains various memory management algorithms like overlays, swapping, paging and segmentation. Overlays divide a program into instruction sets that are loaded and unloaded as needed. Swapping loads entire processes into memory for execution then writes them back to disk. Paging and segmentation are used to map logical addresses to physical addresses through page tables and segment tables respectively. The document compares advantages and limitations of these approaches.
Memory management is the act of managing computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when no longer needed. This is critical to any advanced computer system where more than a single process might be underway at any time
Memory management is the method by which an operating system handles and allocates primary memory. It tracks the status of memory locations as allocated or free, and determines how memory is distributed among competing processes. Memory can be allocated contiguously or non-contiguously. Contiguous allocation assigns consecutive blocks of memory to a process, while non-contiguous allocation allows a process's memory blocks to be scattered across different areas using techniques like paging or segmentation. Paging divides processes and memory into fixed-size pages and frames to allow non-contiguous allocation while reducing fragmentation.
The document discusses memory management techniques used in operating systems. It describes logical vs physical addresses and how relocation registers map logical addresses to physical addresses. It covers contiguous and non-contiguous storage allocation, including paging and segmentation. Paging divides memory into fixed-size frames and pages, using a page table and translation lookaside buffer (TLB) for address translation. Segmentation divides memory into variable-sized segments based on a program's logical structure. Virtual memory and demand paging are also covered, along with page replacement algorithms like FIFO, LRU and optimal replacement.
This document provides an overview of memory management techniques in operating systems, including both static and dynamic allocation approaches. It discusses fixed and variable partitioning for static allocation, as well as first-fit, next-fit, best-fit, and worst-fit algorithms for dynamic allocation. The document also covers fragmentation, base-limit registers, swapping, paging, and segmentation for virtual memory management. The key aspects of paging include using page tables to map virtual to physical addresses, allowing sharing and abstracting physical organization. Segmentation divides memory into logical segments specified by segment tables.
This presentation describes about the various memory allocation methods like first fit, best fit and worst fit in memory management and also about fragmentation problem and solution for the problem.
This document summarizes and compares paging and segmentation, two common memory management techniques. Paging divides physical memory into fixed-size frames and logical memory into same-sized pages. It maps pages to frames using a page table. Segmentation divides logical memory into variable-sized segments and uses a segment table to map segment numbers to physical addresses. Paging avoids external fragmentation but can cause internal fragmentation, while segmentation avoids internal fragmentation but can cause external fragmentation. Both approaches separate logical and physical address spaces but represent different models of how a process views memory.
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.
This document discusses different memory management techniques used in operating systems. It begins by describing the basic components and functions of memory. It then explains various memory management algorithms like overlays, swapping, paging and segmentation. Overlays divide a program into instruction sets that are loaded and unloaded as needed. Swapping loads entire processes into memory for execution then writes them back to disk. Paging and segmentation are used to map logical addresses to physical addresses through page tables and segment tables respectively. The document compares advantages and limitations of these approaches.
Virtual Memory
• Copy-on-Write
• Page Replacement
• Allocation of Frames
• Thrashing
• Operating-System Examples
Background
Page Table When Some PagesAre Not in Main Memory
Steps in Handling a Page Fault
The document discusses memory management in operating systems. It covers key concepts like logical versus physical addresses, binding logical addresses to physical addresses, and different approaches to allocating memory like contiguous allocation. It also discusses dynamic storage allocation using a buddy system to merge adjacent free spaces, as well as compaction techniques to reduce external fragmentation by moving free memory blocks together. Memory management aims to efficiently share physical memory between processes using mechanisms like partitioning memory and enforcing protection boundaries.
This Presentation is for Memory Management in Operating System (OS). This Presentation describes the basic need for the Memory Management in our OS and its various Techniques like Swapping, Fragmentation, Paging and Segmentation.
a glance on memory management in operating system.
this note is useful for those who are keen to know about how the OS works and a brief explanation regarding several terms such
-paging
segmentation
fragmentation
virtual memory
page table
to A Level A2 Computing students, this light note may be helpful for your revision
The document discusses different memory management techniques used in operating systems. It begins with an overview of processes entering memory from an input queue. It then covers binding of instructions and data to memory at compile time, load time, or execution time. Key concepts discussed include logical vs physical addresses, the memory management unit (MMU), dynamic loading and linking, overlays, swapping, contiguous allocation, paging using page tables and frames, and fragmentation. Hierarchical paging, hashed page tables, and inverted page tables are also summarized.
n computer operating systems, demand paging is a method of virtual memory management. In a system that uses demand paging, the operating system copies a disk page into physical memory only if an attempt is made to access it and that page is not already in memory
Virtual memory is a technique that allows a program to use more memory than the amount physically installed on the system. When physical memory is full, infrequently used pages are written to disk. This allows processes with memory needs greater than physical memory to run. Common page replacement algorithms are first-in, first-out (FIFO), least recently used (LRU), and optimal (OPT) which replaces the page not used for the longest time. Virtual memory provides benefits like allowing more programs to run simultaneously but has disadvantages like reduced performance and system stability.
Virtual memory management techniques allow processes to access memory in a virtual address space that is larger than the actual physical memory. There are three main techniques:
1. Demand paging only loads pages into memory when they are needed, reducing I/O and memory usage but increasing access time due to page faults.
2. Copy-on-write shares pages between processes until a page is modified, then it is copied to avoid overwriting another process's page.
3. Page replacement algorithms select victim pages to remove from memory and write to disk when new pages are needed. Least recently used is commonly used but not optimal.
The document discusses various memory management techniques used by operating systems including memory allocation, paging, segmentation, virtual memory and page replacement algorithms. It provides details on how operating systems manage processes in memory using techniques like memory mapping, context switching, swapping and fragmentation handling. Various address translation mechanisms like logical, physical and virtual addresses are also summarized along with common page replacement algorithms like FIFO, LRU, OPT and their working.
Operating system paging and segmentationhamza haseeb
This document discusses paging and segmentation in operating systems. Paging divides memory into fixed-size pages for faster data access and allows physical addresses to be non-contiguous. It has advantages like no external fragmentation but disadvantages like internal fragmentation and consuming memory for page tables. Segmentation divides memory into segments of varying lengths and permissions for memory protection. It has advantages like no internal fragmentation and less memory used for segment tables, while lending itself to data sharing and protection but has the disadvantage of a more costly memory management algorithm.
This document summarizes a presentation on virtual memory given by 5 students for their Computer Architecture and Organization course. It includes definitions of virtual memory, how it works using demand paging and segmentation, why it is used to support multitasking and large programs, the mapping and address translation processes, page tables, page size and faults, and advantages and disadvantages of virtual memory such as protection, sharing, and memory and performance overhead.
Cache memory is a small, fast memory located close to the processor that stores frequently accessed data from main memory. When the processor requests data, the cache is checked first. If the data is present, there is a cache hit and the data is accessed quickly from the cache. If not present, there is a cache hit and the data must be fetched from main memory, which takes longer. Cache memory relies on principles of temporal and spatial locality, where frequently and nearby accessed data is likely to be needed again soon. Mapping functions like direct, associative, and set-associative mapping determine how data is stored in the cache. Replacement policies like FIFO, LRU, etc. determine which cached data gets replaced when new
Virtual memory allows programs to access more memory than the physical memory available on a computer by storing unused portions of memory on disk. It was first developed in 1959-1962 at the University of Manchester. Key aspects of virtual memory include: dividing memory into pages that can be swapped between disk and physical memory as needed, using page tables to map virtual to physical addresses, and page replacement algorithms like LRU to determine which pages to swap out. Virtual memory provides benefits like running more programs simultaneously but can reduce performance due to disk access times.
This chapter discusses early memory management techniques including fixed partitions, dynamic partitions, and relocatable dynamic partitions. It describes how these systems allocate and deallocate memory using concepts like first-fit and best-fit allocation, and how they utilize compaction to optimize memory usage. Special registers are used to track memory locations as programs are relocated during compaction.
Contiguous allocation is an early method for allocating main memory between the operating system and user processes. Each process is contained within a single contiguous section of memory. Relocation and limit registers are used to protect processes from each other and allow transient changes to the operating system. Multiple-partition allocation allocates variable sized partitions to processes out of memory holes. Storage allocation approaches like first-fit and best-fit are used to allocate partitions from the holes. Fragmentation can occur both externally and internally, taking up space that cannot be used.
This document discusses different approaches to memory management in operating systems. It begins by describing monoprogramming without swapping or paging, where one program uses all available memory at a time. It then describes multiprogramming using fixed memory partitions, either with separate queues for each partition or a single queue. The challenges of relocation and protection when programs are loaded at different addresses are also covered. Finally, it introduces the concepts of swapping and virtual memory for handling situations where not all active processes fit in main memory.
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.
The document summarizes the boot process of an operating system. It begins with the BIOS executing code from the ROM chip and loading the master boot record (MBR) from the hard disk. The MBR then loads the volume boot record (VBR) from the active partition, which loads the second stage boot loader like NTLDR or GRUB. This boot loader then loads and executes the kernel, which initializes the filesystem and launches core processes.
- Physical storage media can be classified by access speed, cost per unit of data, and reliability. This includes cache, main memory, flash memory, magnetic disks, optical disks, and magnetic tapes.
- Faster but more expensive media like cache and main memory are primary storage, while magnetic disks represent secondary storage. Tapes and optical disks provide tertiary, offline storage.
- Volatility also differs, with volatile storage like main memory losing data on power loss, while nonvolatile media like disks and flash retain data. The database typically resides on nonvolatile secondary storage for long-term access.
Virtual Memory
• Copy-on-Write
• Page Replacement
• Allocation of Frames
• Thrashing
• Operating-System Examples
Background
Page Table When Some PagesAre Not in Main Memory
Steps in Handling a Page Fault
The document discusses memory management in operating systems. It covers key concepts like logical versus physical addresses, binding logical addresses to physical addresses, and different approaches to allocating memory like contiguous allocation. It also discusses dynamic storage allocation using a buddy system to merge adjacent free spaces, as well as compaction techniques to reduce external fragmentation by moving free memory blocks together. Memory management aims to efficiently share physical memory between processes using mechanisms like partitioning memory and enforcing protection boundaries.
This Presentation is for Memory Management in Operating System (OS). This Presentation describes the basic need for the Memory Management in our OS and its various Techniques like Swapping, Fragmentation, Paging and Segmentation.
a glance on memory management in operating system.
this note is useful for those who are keen to know about how the OS works and a brief explanation regarding several terms such
-paging
segmentation
fragmentation
virtual memory
page table
to A Level A2 Computing students, this light note may be helpful for your revision
The document discusses different memory management techniques used in operating systems. It begins with an overview of processes entering memory from an input queue. It then covers binding of instructions and data to memory at compile time, load time, or execution time. Key concepts discussed include logical vs physical addresses, the memory management unit (MMU), dynamic loading and linking, overlays, swapping, contiguous allocation, paging using page tables and frames, and fragmentation. Hierarchical paging, hashed page tables, and inverted page tables are also summarized.
n computer operating systems, demand paging is a method of virtual memory management. In a system that uses demand paging, the operating system copies a disk page into physical memory only if an attempt is made to access it and that page is not already in memory
Virtual memory is a technique that allows a program to use more memory than the amount physically installed on the system. When physical memory is full, infrequently used pages are written to disk. This allows processes with memory needs greater than physical memory to run. Common page replacement algorithms are first-in, first-out (FIFO), least recently used (LRU), and optimal (OPT) which replaces the page not used for the longest time. Virtual memory provides benefits like allowing more programs to run simultaneously but has disadvantages like reduced performance and system stability.
Virtual memory management techniques allow processes to access memory in a virtual address space that is larger than the actual physical memory. There are three main techniques:
1. Demand paging only loads pages into memory when they are needed, reducing I/O and memory usage but increasing access time due to page faults.
2. Copy-on-write shares pages between processes until a page is modified, then it is copied to avoid overwriting another process's page.
3. Page replacement algorithms select victim pages to remove from memory and write to disk when new pages are needed. Least recently used is commonly used but not optimal.
The document discusses various memory management techniques used by operating systems including memory allocation, paging, segmentation, virtual memory and page replacement algorithms. It provides details on how operating systems manage processes in memory using techniques like memory mapping, context switching, swapping and fragmentation handling. Various address translation mechanisms like logical, physical and virtual addresses are also summarized along with common page replacement algorithms like FIFO, LRU, OPT and their working.
Operating system paging and segmentationhamza haseeb
This document discusses paging and segmentation in operating systems. Paging divides memory into fixed-size pages for faster data access and allows physical addresses to be non-contiguous. It has advantages like no external fragmentation but disadvantages like internal fragmentation and consuming memory for page tables. Segmentation divides memory into segments of varying lengths and permissions for memory protection. It has advantages like no internal fragmentation and less memory used for segment tables, while lending itself to data sharing and protection but has the disadvantage of a more costly memory management algorithm.
This document summarizes a presentation on virtual memory given by 5 students for their Computer Architecture and Organization course. It includes definitions of virtual memory, how it works using demand paging and segmentation, why it is used to support multitasking and large programs, the mapping and address translation processes, page tables, page size and faults, and advantages and disadvantages of virtual memory such as protection, sharing, and memory and performance overhead.
Cache memory is a small, fast memory located close to the processor that stores frequently accessed data from main memory. When the processor requests data, the cache is checked first. If the data is present, there is a cache hit and the data is accessed quickly from the cache. If not present, there is a cache hit and the data must be fetched from main memory, which takes longer. Cache memory relies on principles of temporal and spatial locality, where frequently and nearby accessed data is likely to be needed again soon. Mapping functions like direct, associative, and set-associative mapping determine how data is stored in the cache. Replacement policies like FIFO, LRU, etc. determine which cached data gets replaced when new
Virtual memory allows programs to access more memory than the physical memory available on a computer by storing unused portions of memory on disk. It was first developed in 1959-1962 at the University of Manchester. Key aspects of virtual memory include: dividing memory into pages that can be swapped between disk and physical memory as needed, using page tables to map virtual to physical addresses, and page replacement algorithms like LRU to determine which pages to swap out. Virtual memory provides benefits like running more programs simultaneously but can reduce performance due to disk access times.
This chapter discusses early memory management techniques including fixed partitions, dynamic partitions, and relocatable dynamic partitions. It describes how these systems allocate and deallocate memory using concepts like first-fit and best-fit allocation, and how they utilize compaction to optimize memory usage. Special registers are used to track memory locations as programs are relocated during compaction.
Contiguous allocation is an early method for allocating main memory between the operating system and user processes. Each process is contained within a single contiguous section of memory. Relocation and limit registers are used to protect processes from each other and allow transient changes to the operating system. Multiple-partition allocation allocates variable sized partitions to processes out of memory holes. Storage allocation approaches like first-fit and best-fit are used to allocate partitions from the holes. Fragmentation can occur both externally and internally, taking up space that cannot be used.
This document discusses different approaches to memory management in operating systems. It begins by describing monoprogramming without swapping or paging, where one program uses all available memory at a time. It then describes multiprogramming using fixed memory partitions, either with separate queues for each partition or a single queue. The challenges of relocation and protection when programs are loaded at different addresses are also covered. Finally, it introduces the concepts of swapping and virtual memory for handling situations where not all active processes fit in main memory.
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.
The document summarizes the boot process of an operating system. It begins with the BIOS executing code from the ROM chip and loading the master boot record (MBR) from the hard disk. The MBR then loads the volume boot record (VBR) from the active partition, which loads the second stage boot loader like NTLDR or GRUB. This boot loader then loads and executes the kernel, which initializes the filesystem and launches core processes.
- Physical storage media can be classified by access speed, cost per unit of data, and reliability. This includes cache, main memory, flash memory, magnetic disks, optical disks, and magnetic tapes.
- Faster but more expensive media like cache and main memory are primary storage, while magnetic disks represent secondary storage. Tapes and optical disks provide tertiary, offline storage.
- Volatility also differs, with volatile storage like main memory losing data on power loss, while nonvolatile media like disks and flash retain data. The database typically resides on nonvolatile secondary storage for long-term access.
Operating System
Topic Memory Management
for Btech/Bsc (C.S)/BCA...
Memory management is the functionality of an operating system which handles or manages primary memory. Memory management keeps track of each and every memory location either it is allocated to some process or it is free. It checks how much memory is to be allocated to processes. It decides which process will get memory at what time. It tracks whenever some memory gets freed or unallocated and correspondingly it updates the status.
This document discusses different approaches to memory management in computer systems. It explains that memory plays a central role, with the CPU and I/O system interacting with memory. It then describes four approaches to memory allocation and management: contiguous storage allocation, non-contiguous storage allocation, virtual storage using paging, and virtual storage using segmentation. Paging divides memory into fixed-size frames and logical memory into same-sized pages, using a page table to map logical to physical addresses. Segmentation divides a program into variable-sized segments and uses a segment table to map two-dimensional physical addresses. The most efficient approach sometimes combines paging and segmentation.
The document discusses memory management techniques used in operating systems. It covers logical versus physical address spaces and introduces paging as a memory management technique. Paging divides both main memory and disk storage into fixed-sized pages. Each process has a page table containing entries for its pages, with each entry mapping a page to a frame in main memory if present or being invalid if on disk. The CPU address is divided into a page number to index the table and an offset to access within the page.
UNIT 3-EXPLAINING THE MEMORY MANAGEMENT LOGICAL AND AND PHYSICAL DATA FLOW DI...LeahRachael
The document discusses different memory management techniques used in operating systems. It describes logical and physical addresses, and how memory management is the responsibility of the operating system. It then explains address binding, which maps logical addresses to physical addresses. Next, it covers overlays, which allow multiple programs to share memory by swapping parts in and out. It notes the advantages and disadvantages of overlays. Finally, it briefly discusses contiguous allocation, which allocates memory to a process in a single continuous block.
This document discusses memory management techniques in operating systems. It defines memory management as the functionality that handles primary memory and moves processes between main memory and disk. It describes process address spaces and different types of addresses. It also covers static vs dynamic loading and linking, swapping, memory allocation, fragmentation, paging, segmentation, and address translation. Paging breaks processes into fixed-size blocks called pages, while segmentation divides processes into variable-length segments. The operating system uses techniques like page mapping tables, segment maps, and memory compaction to manage memory.
Memory management handles allocation of memory to processes and tracks used and free memory. It uses techniques like paging, segmentation, and dynamic allocation from a heap. Paging maps logical addresses to physical pages, avoiding external fragmentation. Segmentation divides memory into logical segments of varying sizes. Dynamic allocation fulfills requests from the heap, managing free blocks and avoiding fragmentation and memory leaks.
The document discusses various topics related to memory management in operating systems including swapping, contiguous memory allocation, paging, segmentation, virtual memory concepts like demand paging, page replacement, and thrashing. It provides details on page tables, segmentation hardware, logical to physical address translation, and performance aspects of demand paging. The key aspects covered are memory management techniques to overcome fragmentation and enable efficient use of limited main memory.
This document provides an introduction to memory management techniques in operating systems. It discusses the differences between logical and physical addresses, the role of the memory management unit (MMU) in mapping logical to physical addresses, and memory allocation schemes including static contiguous allocation with equal or unequal partitions, dynamic contiguous allocation, and non-contiguous allocation using paging and segmentation. It also covers dynamic relocation, hardware support via relocation and limit registers, swapping, and fragmentation. The goal of memory management is to efficiently allocate and deallocate memory to running processes.
This document discusses memory management and paging in operating systems. It explains that memory management allocates space for application routines and prevents interference between programs. The memory hierarchy includes main memory, cache memory, and secondary storage. Paging is a memory management technique that divides processes and main memory into equal pages. It allows processes to be non-contiguous in memory. The operating system uses page tables to map logical addresses to physical addresses stored across different pages and frames. Paging reduces external fragmentation but can cause internal fragmentation.
1) Virtual memory simplifies address translation by creating a virtual memory space that contains the operating system and application programs, even though it does not physically exist.
2) Virtual memory is divided into two components - the first occupies real memory and contains the operating system and page pool, while the second occupies external storage and holds application programs, with pages swapped between real memory and external storage.
3) Address translation under virtual memory uses segment tables and page tables to map virtual addresses to physical addresses.
Main memory is where programs are loaded to run on the CPU. There are several techniques for managing memory allocation and binding programs to addresses in memory, including compile-time, load-time, and execution-time binding. Memory management is needed to map logical addresses used by programs to physical addresses in memory. Paging is a memory management technique that divides memory into pages to allow non-contiguous allocation and reduce fragmentation.
Operating systems use main memory management techniques like paging and segmentation to allocate memory to processes efficiently. Paging divides both logical and physical memory into fixed-size pages. It uses a page table to map logical page numbers to physical frame numbers. This allows processes to be allocated non-contiguous physical frames. A translation lookaside buffer (TLB) caches recent page translations to improve performance by avoiding slow accesses to the page table in memory. Protection bits and valid/invalid bits ensure processes only access their allocated memory regions.
Memory Management in Operating Systems for allVSKAMCSPSGCT
The document discusses memory management techniques used in computer systems. It describes the memory hierarchy from fast registers to slower main memory and disk. Memory management aims to efficiently allocate memory for multiple processes while providing protection, relocation, sharing and logical organization. Techniques include contiguous allocation, fixed and dynamic partitioning, paging using page tables, segmentation using segment tables, and swapping processes in and out of memory. Hardware support through relocation registers, memory management units, translation lookaside buffers and associative memory help map logical to physical addresses efficiently.
The document discusses memory management requirements and techniques. The principal responsibilities of memory management are to bring processes into memory for processor execution to ensure sufficient ready processes, and to handle the movement of information between logical and physical memory levels on behalf of the programmer. Memory can be partitioned using fixed, dynamic, or buddy system approaches. Paging and segmentation divide processes into uniform and variable sized chunks respectively and use address translation via tables to map virtual to physical addresses during relocation.
Magnetic disks provide most secondary storage and are relatively simple. Each disk contains one or more flat, circular platters coated with magnetic material. Disks are logically divided into tracks and sectors for reading and writing data. Disks spin rapidly and have read/write heads that can move to different tracks on the platters. Disk scheduling algorithms like SSTF aim to minimize access times by prioritizing requests located near the heads' current position. Disks can be attached directly via I/O ports or over a network using NAS or SAN storage. Disk management includes formatting, handling bad blocks, and using swap space on disk as an extension of main memory.
This document provides an introduction to parallel computing. It discusses serial versus parallel computing and how parallel computing involves simultaneously using multiple compute resources to solve problems. Common parallel computer architectures involve multiple processors on a single computer or connecting multiple standalone computers together in a cluster. Parallel computers can use shared memory, distributed memory, or hybrid memory architectures. The document outlines some of the key considerations and challenges in moving from serial to parallel code such as decomposing problems, identifying dependencies, mapping tasks to resources, and handling dependencies.
The document discusses Java packages. The key points are:
- Packages are containers that group related classes and interfaces together. They allow for organizing code and uniquely naming classes.
- The core Java packages are java.lang, java.util, java.io, java.awt, java.net, and java.applet. They contain fundamental classes for various purposes.
- To use classes from a package, the package must be imported or the fully qualified class name can be used. The package statement declares user-defined packages.
This document discusses exceptions in Java programs. It defines exceptions as runtime errors that occur when an unexpected condition arises. It describes different types of errors like runtime errors, logic errors, and syntax errors. It provides an example Java program that generates an exception by dividing a number by zero. Finally, it explains Java's exception handling mechanisms like try, catch, throw, throws and finally keywords to detect and manage exceptions.
PHP is an open source scripting language used for web development that can be embedded into HTML. It is executed on the server and allows code to be enclosed in special PHP tags. Variables in PHP start with a $ sign and automatically take the correct data type. Strings can be concatenated using the . operator and PHP supports various operators like arithmetic, assignment, comparison, and logical for working with values.
This document discusses static methods and abstract classes in PHP. Static methods can be called directly on a class without creating an instance. Abstract classes contain at least one abstract method that is declared but not implemented, requiring child classes to implement the method. The example shows an abstract Car class with an intro() method, and child classes Audi, Volvo and Citroen that implement intro() uniquely for each class.
Operating System File Management Unit v.pptxSanthiNivas
This document discusses file management. It begins by introducing the file manager and its responsibilities, which include file storage tracking, policy implementation, file allocation and deallocation. The file manager determines file storage locations and system/user access based on policy. It then defines key concepts like fields, records, files, databases, program files and data files. It describes how users interact with the file manager using logical commands and describes typical volume configurations including the master file directory and subdirectories. It concludes by discussing file descriptors and file naming conventions.
Input devices such as keyboards, mice, joysticks, light pens, and trackballs are used to provide data and control signals to computers. Keyboards allow text input and contain 104-105 keys laid out like a typewriter. Mice are popular pointing devices with left and right buttons used to control cursor position but not enter text. Other pointing devices include joysticks and light pens. Trackballs are upside-down mice located in front of laptop keyboards. Output devices like monitors, printers, and projectors receive computer data and translate it into visual, audio, textual, or printed forms for users.
1. The document provides information on HTML including definitions of key terms like HTML, URL, and browser. It also covers topics such as creating basic HTML documents, using headings, paragraphs, breaks, and horizontal rules.
2. The document discusses how to format text using bold, italics, underline, and color. It also covers inserting special characters and symbols.
3. The document describes how to create different types of lists like unordered lists, ordered lists, and defined lists as well as nesting lists.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help boost feelings of calmness, happiness and focus.
It gives detailed description about Points, Lines, Attributes of Output Primitives, Line Functions, Line Drawing Algorithms, DDA Line drawing algorithms, Bresenham’s Line Algorithm, Circle Generating Algorthims
This PPT gives detailed information about Computer Graphics, Raster Scan System, Random Scan System, CRT Display, Color CRT Monitors, Input and Output Devices
This document discusses various page layout and formatting options in Microsoft Word, including changing the page size and orientation, paper type, width and height, layout, background, inserting and deleting pages, templates, and creating and editing templates. Key steps are provided for changing common page settings like size, adding or removing pages, and using templates to format documents.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
A workshop hosted by the South African Journal of Science aimed at postgraduate students and early career researchers with little or no experience in writing and publishing journal articles.
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
Assessment and Planning in Educational technology.pptxKavitha Krishnan
In an education system, it is understood that assessment is only for the students, but on the other hand, the Assessment of teachers is also an important aspect of the education system that ensures teachers are providing high-quality instruction to students. The assessment process can be used to provide feedback and support for professional development, to inform decisions about teacher retention or promotion, or to evaluate teacher effectiveness for accountability purposes.
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2. Memory management : Early systems
Memory Allocation schemes:
Single user configurations
Fixed Partitions
Dynamic Partitions
Relocatable Dynamic Partitions
3. • Main memory –temporary memory(RAM)
• Secondary memory –Permanent memory(ROM)
• Single user contiguous scheme:
• Single Contiguous Memory Allocation is a simple
memory allocation scheme,
• Requires no special hardware features. Entire available memory
is allocated to a single job.
4. • In this scheme of allocation, the main memory is divided into 2
contiguous regions.
• One portion is permanently allocated to the operating system. All the remaining
memory is available for a single job, which has to be processed. The Job actually
uses some part of the allocated memory.
• Two h/w items need:
• 1.Register to store address
• 2. Accumulator keep track of the size ,the Program being read into memory
• It doesn’t support multiprogramming or N/W, handle one job at a time.
5. • All the computer's memory, usually with, the exception of a small portion
reserved for the operating system.
• Early years computer were physically large & low memory capacity.
• If the program doesn’t fit ,either the main memory must be increased or
program must be modified.
6. • Advantage:
• 1. Simple Allocation
• 2. Entire scheme requires less memory
• 3. Easy to implement & use.
• Disadvantage:
• 1. Memory & CPU not fully Utilized
• 2. User program is being limited.
7. • It allow multiprogramming within main memory-one partition for each job.
• Each Memory partition was designed when the system power on, and to be
reconfigured when the system shut down(Restart).
• Protect job’s memory space
• Once Partition assigned to a job , no other job will assign to that partition.
• Fixed partition allocation ,protection was mandatory for each partitions.
• Joint responsibility OS –H/W.
Fixed / Static Partitions:
8. • Its better than single contiguous allocation,
because it allow several program into
main memory at the same time.
11. DYNAMIC PARTITION:
• Partitions(MM) are created dynamically.
• Dynamic partition utilizes the memory when the 1st job load , jobs are not
in same size.
• It fit into the available space based on priority. (First come – First served
bases.).
• Memory creates fragment of free memory b/w blocks called external
fragmentation.
100k
150k
200k
OS
12. Best fit vs First fit:
• Best fit:
• The best fit deals with allocating the smallest free partition which meets
the requirement of the requesting process. This algorithm first searches the
entire list of free partitions and considers the smallest hole that is adequate.
It then tries to find a hole which is close to actual process size needed.
• J1-135k 100k - waiting job
• j2-75k 150k =15free
• j3-165k 200k =35 free
• Disadvantage: upcoming job must be wait till memory to be arrange
75k
165k
75k
135k
13. First fit
• In the first fit approach is to allocate the first free partition or hole large
enough which can accommodate the process. It finishes after finding
the first suitable free partition.
• 100k - waiting job
• 150k =100free
• 200k =150 free
J1-
10k
J2-
50k
J3-
50k
J4-
50k
14. Deallocation:100k free50k called de-allocation
• Deallocation of memory by the Operating System (OS) is a way to free the
Random Access Memory (RAM) of finished processes. New processes
are allocated again. This is how the OS works
with allocation and deallocation.
• In fixed partition- when job is completed memory manager resets the
memory block free –to store another job.
• 1.when the block to be de-allocated is adjacent(3-free-busy-free) to another
free block.
• 2.when the block to be de-allocated is b/w two free block.
• 3.when the block to be de-allocated is isolated from other free block.
J1-
50k
J1-50k
50k
15. Null entry:
• the status is changed from “a null entry to free” – indicate that a
new block of memory is available.
• When the null entry found, the beginning memory location of the
terminating job is entered in the beginning address column,(1000)
• the job size is entered under the memory block size column.
16. Relocatable dynamic partitions:
• In relocatable dynamic partition, memory manager in operating system
relocates the program, that is all empty blocks are gathered to form one
single block of large memory enough to accommodate some or all of the
jobs waiting in the queue.
• Compaction(defragmentation & garbage collection)- combining all the
empty memory spaces together.
17. Compaction
• it’s not a easy task, every program memory must be reallocated, so they are
contiguous, - every address, every reference to an address within the each
program must be adjusted to new location in memory.- OS must be
differentiate ADDRESS & DATA VALUE.
• All numbers are stored in memory as binary values.
• Assembly language instruction to ADD integer 1 to I,
• Instruction like ADDI A ,1 ex: (A+1)
18. Flag:
• A flag is a value that acts as a signal for a function or process. The value of
the flag is used to determine the next step of a program.
• Flags are often binary flags, which contain a Boolean value (true or false).
However, not all flags are binary, meaning they can store a range of values.
19. After relocation & compaction – free list & busy list updated
Show block of free memory show the new location of the job
under the process
Register: used to relocate the memory
1.Bound Register- store highest/lowest memory location
2.Relocation Register-value must be added to each address
referenced in program(correct memory address)
20. It has 3 approach in relocating memory:
• One is ->100k -75% used
• Balance 25% memory wasted
• Second is: compact memory only- constant checking of entry queue
• Make jobs were waiting.
• 3rd one:
• Prescribed amount of time elapsed, if chosen time is too small , system will
spend more time on compaction on processing.
21. PAGED MEMORY ALLOCATION:
• Before job loaded into memory divided into some parts called page-in memory location its called page frames.
• Paged memory allocation – based on dividing each incoming job into pages of equal size- some OS page size is equal size of
memory Block size.
• Page can be stored in any available page frame in main memory
• Operating systems, paging is a memory management scheme -a computer stores and retrieves data from secondary storage for
use in main memory. In this scheme, the operating system retrieves data from secondary storage in same-size blocks called
pages.
• Advantage : storing program is Non-contiguous in Main memory- so its more efficiently use any page of any job
22. • Before executing a program, memory manager prepares it by:
1) Determining the number of pages in the program
2) Locating enough empty “page frames” in main memory
3) Loading all of the program’s page into them(MM).
• 1st page contains first instruction.
• Last page contains last instruction
23. • job1 divided into 4 pages: page 0,page 1, page 2, page 3,
• Total job size: 350bytes,
• page 0 - 100
• page 1 - 100
• page 2 - 100
• page 3 – 50 (few job size perfectly fill with page size)so internal
fragmentation occurs.
• Next job must be wait till job1 ends.
• If job is Larger than 1100 bytes it never fit to memory.
• It is Non-Contiguous storage.