A computer is an electronic device that processes data according to instructions stored in its memory. It accepts raw data as input, processes the data, stores the results if needed, and provides output. Computers can solve problems quickly and accurately, store and retrieve large amounts of data, and display information through documents and images. The basic components of a computer system are hardware and software. Hardware refers to the physical parts like the processor and memory, while software provides instructions for the hardware to function. Together, hardware and software allow computers to perform a wide range of tasks.

1. Introduction to
computer system

2. What is a computer?
• The term ‘computer’ is derived from the Latin word ‘compute’ which
means to calculate.
• To calculate means to carry out arithmetic and logical evaluations.
• A computer is an electronic, digital, programmable, and automatic machine
• Which takes raw fact as input from the user, processes it, stores it if
necessary and gives meaningful information as output to the user.

3. Importance of Computer
• Solving numerical problems
• Storing and retrieving information
• Creating and displaying document and picture

4. Introduction to computers
• Electronic device operating under the control of instructions stored in its own memory
• that can accept data according to specified rules, produce results and stores the result for
future use.
• A computer is a programmable machine capable of :
 taking input raw data through the input devices such as mouse, keyboard or any other input
devices.
 Storing the input data into main memory and disks such hard disk, cd or any other medium
 Processing it at the Central Processing Unit (CPU)
 Giving out the result as output on the screen or the any visual display unit.

5. The Input-Process-Output Concept
• Computer is an electronic device that accepts data, processes data, generates
output and stores data.
• concept of generating output information from the input is referred as input
process output concept.

6. Input Process Output Concept
• Input: the computer accepts input data from the user via an input device like
a keyboard. The input data can be characters, word, text, sound, images,
documents etc.
• Process: the computer processes the input data, for this it performs some
actions on the data by using the instructions or programs given by the user
of the data.(The action could be arithmetic or logic calculations, editing or
modifying a document, etc.) during processing data instructions and output
are stored temporarily in computers main memory.

7. • Output: The output is the result generated after the processing of data. The
output may be in the form of text, sound, image, documents, etc.
• The computer may display the output on the monitor, or send to the printer
for printing or play the output.
• Storage: The input data, instructions and output are stored permanently in
the secondary storage devices like disk or tape. The stored data can be
retrieved whenever required.

8. Characteristics of computer
• Word length
i. A digital computer operates on binary digits- 0 and 1
ii. It manipulates data only in the term of 0 and 1.
iii. the number of bits a computer can process at a time in parallel is called its
word length
iv. Word length varies as 8, 16, 32 or 64 bits. It is the measurement of computing
power of a computer i.e. the longer the word length the more powerful the
computer is.

9. Characteristics of computer
• Speed
i. The time take by a computer to perform any task is called the speed of the
computer.
ii. It takes only few seconds for calculations that we take hours to complete.
iii. The speed of computer is in term of micro seconds (10^-6 part of a
second) or Nano-seconds (10^-9 part of a second)

10. Characteristics of computer
• Storage
i. The computer has mass storage section where we can store large volume of data
for future work.
ii. Such data can be easily accessible whenever needed
iii. Magnetic disk magnetic tapes and optical disk are used as the mass storage devices
iv. The storage capacity of computers is measured in term of KB , MB , GB and TB,
etc.
v. The smallest unit is bit and the unit of 8 bits is1 byte.

11. Characteristics of computer
• Accuracy
i. A computer is an accurate machine
ii. The degree of accuracy of a computer is very high and every calculations
is performed with the same accuracy.
iii. It can perform large number of tasks without errors nut if we feed wrong
data to the computer it returns the same wrong information called
GIGO(Garbage In Garbage Out)

12. Characteristics of computer
• Diligence
i. It is the capacity of performing same tasks repeatedly multiple times
without feeling tiredness, boring, lack of concentration and fatigue with
same speed and accuracy.
ii. It can work for hours without creating an error.
iii. If millions of calculations have to be performed, a computer will perform
every calculations with same accuracy .

13. Characteristics of computer
• Versatility
i. The feature of a computer to perform more than one task having different
characteristics is called versatility of computer
ii. It can carry out processes ranging from simple mathematical calculations to highly
complex and logical evaluations for any extended period of time
iii. Computers are being used in diff areas for diff tasks
iv. The capability of a comp to perform diff tasks and has a wide range of areas
depending upon different programs used in it is known as versatility .

14. Characteristics of computer
• Non-Intelligent
i. A comp is a dumb machine and it cannot do any work without instructions from user .
ii. It performs the instructions at tremendous speed and with accuracy,
iii. It is you to decide what you want to do and in what sequence
iv. So a computer cannot take its own decision as you can.
v. It has no feelings & emotions,
vi. It has no feelings emotions taste thus it does not get tired even after long hours of work.
vii. It doesn't distinguish between users

15. Computer System
• A computer system is a combination of hardware and software that is used to
perform a wide variety of tasks, such as processing data, communicating with other
devices, and running applications.
• Hardware refers to the physical components of a computer system, such as the
processor, memory, storage, and input/output devices.
• Software refers to the programs and operating systems that run on the computer
and provide instructions for the hardware to follow.
• Together, the hardware and software work together to allow a computer to process
information, store and retrieve data, and perform a variety of functions.

16. Computers perform 5 basic operations
 To convert raw data into information computer performs:
Inputting: It is the process of entering the data and instructions to the comp
by any input devices.
o inputting of data and instructions is very important because of al the
manipulation and processing will be performed on the inputted data, where
as instruction tells the computer what to do with the inputted data

17. Storing: Storing basically means saving data and instructions so that they are
available for initial or additional processing as and when required.
Processing: Processing means performing mathematical or logical operations on
data in order to convert them into meaningful information.
Outputting: the process of producing useful information or results for the users,
such as a printed report or displayed o the monitor is termed as outputting
Controlling: It means directing the manner and sequence in which all the
operations( inputting, storing, processing, outputting) are performed.

18. Applications Of Computers
• Bank – electronic money transfer, statistical report, vouchers, balance sheet,
etc. ATM, EFTS, etc. are computerized services provided by bank
• Education – teaching learning tool, result processing, student data
processing, question preparations, online education, etc.
• Industries- research, budgeting and processing, robots used in complicated
industrial processes
• Research hospitals data processing science and engineering government
business and advertisement library, etc.

19. Classification of computers
• Computers can be classified as general purpose and special purpose
• Special purpose refers to Analog and Hybrid Computers whereas general
purpose computers are digital computers.
• According to functional style also we have three types of computers:
I. Analog
II. Digital
III. Hybrid

20. Computers
On The basis of Work Size Model Brand
Analog Super XT IBM PC
Digital Mainframe AT Apple/ Macintosh
Hybrid Mini
Micro
PS/2

21. Classification o the basis of working principle
(Application or Function)
Analog Computer
Digital Computer
Hybrid Computer

22. Analog Computer
• It is one which operates on continuous data, usually of a physical nature such as length
voltage or currents etc.
• It is a special purpose device dedicated to do a single task
• It is based on analog signals which are continuous signals
• Mainly used in scientific and industrial application.
• Used in hospitals to measure the size of stone in kidney, CT scan
• Its powerful in solving differential equations.
• They represent physical quantities in the form of waves or in continuous form.
• Examples: Plessey, speedometer, thermometer, barometer, etc.

23. Analog Computer
• Plessey • speedometer

24. Digital Computer
• It is the one which works with binary digits (0s and 1s)
• Based on digital signals i.e. discrete signals.
• It does not measure the physical values
• It operates on data, including magnitudes, letters and symbols, that are expressed in
binary form- i.e. using only two digits 0 and 1.
• A general purpose device, dedicated to do multiple tasks.
• Most computers used today are digital computers.
• For example IBM PC, Apple/ Macintosh etc.

25. Digital computers
• IBM PC • Apple/Macintosh

26. Difference Between
Analog Computer
• Work with physical values such as pressure,
temperature, etc.
• Based with continuous data
• Very low accuracy
• Faster than digital
• Single purpose
• It has no or limited storage
• Low cost and portable
• It cannot be reprogrammed
Digital Computer
• Works with binary digits(0s and 1s)
• Based with discrete data
• High accuracy
• Slower than analog
• Multi purpose
• High storage capacity
• Cost is high and easily not portable
• It can be reprogrammed

27. Hybrid Computer
• One that combines the best features of both analog and hybrid computers
• Helps the user to process both continuous and discrete data
• Can convert analog signals into digital signals and digital signals into analog signals.
• Generally used in scientific applications, aero planes, jet planes, industries, hospitals
• High cost and mostly used in hospitals to measure the heart beat of the patient.

28. Classification on the basis of size
Super computers
Mainframe computers
Mini computers
Micro computer

29. Super Computers
• Largest fastest and most expensive computers
• Large memory capacity and very high processing speed
• 10 times more faster than other computers
• Used for solving very difficult and complex problems
• It is multiuser multiprocessor large computer with a very high efficiency
• These computers have multiple CPU that can process multiple instructions at a
time, known as parallel processing
• A number of RISC processors are used.

30. Examples
• CRAY-XMP/14 ETA 10 CDC-205

31. Applications of Super computers
• In Petroleum industry
• Aerospace industry, automobile industry
• Structural mechanics, meteorological
• Biomedical research, weapon research , scientific computing and research,
• Military research and defense systems,
• Encrypting and decrypting sensitive intelligence information
• Study of DNA structure and genetic engineering

32. Mainframe computers
• Large general purpose computer designed for large scale processing
• Very powerful processor large amounts of main memory and a huge backing
storage capacity.
• Accessed through one or more terminals
• Normally they are used in banking, airlines and railways
• Example: IBM 1401, ICL 2959/10, IBM S/390 etc.

33. IBM S/390 IBM 1401

34. Characteristics of mainframe computer
• They are very large in size with large storage capacity and high processing speed.
• They support large number of terminals
• They have centrally located cpu
• It is general purpose computer
• They are used by large agencies and government for large scale data processing
• Consists of multiple processors, GB’s of memory and TB’s of storage and supports
multiple users
• Less expensive than super computer
• They can run multiple operating system hence called virtual machine.

35. Mini Computer
• It is medium size i.e. it is bigger than micro and smaller than mainframe
• Small number of terminals approximately 50
• They are general purpose computers
• Less powerful than mainframe but more powerful than micro computers.
• They are used in medium sized organization
• They are used in business as centralized computer or as internet server
• Less expensive than mainframe but more expensive than micro computers
• Examples: IBM AS, Prime Series, HP 9000, IBM8000 Series, etc.

36. Micro Computer
• Smallest of all and single user
• A micro computer has microprocessor as its CPU.
• Extensively used in home and offices
• They are cheap, compact and can be easily accommodated on a study table
• It supports multimedia , networking, graphics, 3D graphics and games
• It supports different types of operating systems like GUI and CUI
• Diff types of micro computers are: desktop, laptop, palmtop, PDA, smartphones

37. Classification on the basis of Brand
• IBM PC
• IBM Compatible
• Apple/ Macintosh Computer

38. IBM PC
• International Business Machine is the largest computer manufacturing company establishing
in 1924 AD in USA.
• IBM manufactured mainframe computers followed by micro and mini computers
• It produces both hardware and software of computer system
• The computer developed by IBM itself is called IBM PC.
• Also called original or branded computers
• Reliable durable and have better quality but expensive than IBM Compatible
• Designed for professional and scientific problem solver.
• IBM PCs are nearly 28% in the market.

39. IBM Compatibles
• Computers having some functional characteristics and principles of IBM
PCs.
• It can perform all the task that an IBM PC does
• The basic architecture is similar to IBM PC excepting few technologies

40. Apple Macintosh
• series of personal computers designed and developed by Apple Inc
• The Macintosh was the first personal computer to be sold to the general
public with a graphical user interface (GUI) and a mouse.
• The Macintosh is known for its ease of use, reliability, and innovative design.

41. On the basis of Model
• XT Computer
• AT Computer
• PS/2 Computer

42. XT Computer
• XT stands for eXtra Technology and these computer uses CUI (Character
User Interface).
• It is comparatively less flexible and slower than other models
• XT computers can’t run todays versions of software and programs
• Examples: Intel 8085 / 8086 / 8088.

43. AT Computer
• AT stands for Advanced Technology
• these computers are based on GUI (Graphics User Interface).
• Their I/ O device are flexible and faster
• It has processor and large storage capacity, complex calculation.
• Example: Pentium 80286 / 386 / 488.

44. PS / 2 Computer
• PS stands for Personal System.
• It is refinement of AT computer.
• It runs on battery.
• They have faster I /O devices and uses GUI based software.

45. Mobile Computing
• Technology that allows transmission of data, voice and video via a computer or any
other wireless enabled device without having to be connected to a fixed physical link
• Refers to the use of portable devices, such as laptops, tablets, and smartphones, to
access and process information, communicate with others, and perform various
tasks while on the go.
• Allows users to stay connected and productive no matter where they are
• Mobile computing relies on a number of technologies, including wireless
networking, mobile operating systems, and cloud computing.

46. • Mobile computing works based on three concepts
i. Mobile communication
ii. Mobile hardware
iii. Mobile software

47. Mobile communication
The exchange of data and voice using existing wireless networks.
it allows people to stay connected and in touch with others no matter where
they are.
operate over different frequencies and use different technologies to transmit
and receive data

48. Mobile Hardware
• A small and portable computing device with the ability to retrieve and
process data.
• Smartphones, handheld and wearable devices fall under mobile hardware.
• These devices typically have an Operating System (OS) embedded in them
and able to run application software on top of it.
• Equipped with sensors, full-duplex data transmission and have the ability to
operate on wireless networks such as IR, WiFi, and Bluetooth.

49. Mobile Software
• software program which is developed specifically to be run on mobile
hardware
• This is usually the operating system in mobile devices.
• Provide features such as touchscreen, cellular connectivity, Bluetooth, Wi-Fi,
sensors, etc.

50. Characteristics of Mobile Computing
• Portability
• Social Interactivity
• Individual
• Connectivity
• Small Size
• Wireless Communication

51. Principles of Mobile Computing
• Portability – facilitate movement of device within the mobile computing
environment
• Connectivity – availability to continuous connection w/ minimal lag & no
interruption while movement
• Social Interactivity – maintaining the connectivity to collaborate w/ other
users
• Individuality – adapting technology to meet individual needs

52. Anatomy of a Digital Computer

53. The basic computer organization have
following units
• Input unit
• Memory unit
• Processing unit
• Output unit
• CPU
• Registers

54. CPU (Central Processing Unit)
• CPU is also known as the brain of a computer as it executes the program
instructions.
• The CPU has two parts that is
i. Control unit (CU)
ii. ALU (Arithmetic Logic Unit)

55. Control unit (CU)
• tells that how the rest of the computer system carries out a program’s
instructions.
• fetches instructions from memory, decodes them to determine the operation
to be performed, and then sends control signals to the other components to
carry out the operation
• It also retrieves data from memory as needed and stores the results of
operations back in memory.

56. ALU (Arithmetic Logic Unit)
• ALU does two kinds of operations - arithmetical and logical.
• Arithmetical operations of ALU are the fundamental mathematical
operations
• Logical type operation is two pieces of data these are use to compare to see
whether one is equal to, less than or greater than the other one.

57. Memory Unit
• Computer memory is the working storage part or area in the computer.
• There are two types of computer memory: primary memory and secondary
memory.
i. Main memory
ii. Cache memory
iii. Register

58. Main Memory
• RAM is the primary or main memory.
• It is volatile in nature
• It holds the data for a short period of time only, i.e. only until the system is
running.
• Files and instructions are saved in different secondary storage systems and
they are fetched to the RAM before the execution.

59. Cache Memory
• It is the smallest and fastest form of memory.
• The contents that require to be fetched frequently are stored in the cache
memory.
• The processor before looking for the content in RAM checks here and goes
to RAM only if the content isn’t available here.
• Cache memory is always placed between RAM and the processor.

60. Register
• There are special-purpose temporary storage units which are called registers.
• They are the form of memory with the highest transfer speed.
• These registers are used for holding instructions, data and intermediate
results that are currently being processed.

61. Memory and Classification of Memory in
Computer
• Besides processing data and getting the results for immediate use computer is used
for storing data as well.
• there are two types of memory in a computer system,
• one for storing data that are currently being handled by the CPU
• and another for storing data and results for future reference.
• There is a third type of memory as well which is known as internal process memory.
• These are placed either near to the CPU or inside the CPU itself.

62. Memory Representation
• 1 Byte = 8 Bits
• 1 KB = 1024 Bytes
• 1 MB = 1024 KB = 1048576 Bytes
• 1 GB = 1024 MB = 1073741824 Bytes
• 1 TB = 1024 GB = 1099511627776 Bytes

63. • There are mainly two types of memory:
i. Primary Memory
ii. Secondary Memory

64. Primary memory
• Main memory of computer which is used to store the information
(programs and data) that the computer is currently using.
• Primary memory is categorized into two main types:
i. Random Access Memory (RAM)
ii. Read Only Memory (ROM)

65. Random Access Memory (RAM)
• RAM (Random Access Memory) is the internal memory of the CPU for
storing data, program and program result.
• It is read/write memory which stores data until the machine is working.
• RAM is volatile, i.e. data stored in it is lost when we switch of the computer
or if there is a power failure.
• RAM is small, both in terms of its physical size and in the amount of data it
can hold.

66. • RAM is of two types
I. Static RAM (SRAM)
II. Dynamic RAM (DRAM)

67. Static RAM
• The word static indicates that the memory retains its contents as long as
power is being supplied.
• Data is lost when the power gets down due to volatile nature.
• SRAM is used as cache memory and has very fast access.
• SRAM uses multiple transistors (four to six), for each memory cell.
• It does not have a capacitor in each cell.

68. Characteristic of the Static RAM
• It has long life
• There is no need to refresh
• Faster
• Used as cache memory
• Large size
• Expensive
• High power consumption

69. Dynamic RAM (DRAM)
• DRAM, unlike SRAM, must be continually refreshed (recharged) in order to
maintain the data.
• DRAM is used for most system memory because it is cheap and small.
• It uses transistors and capacitors.
• The transistors are arranged in a matrix of rows and columns.
• The capacitor holds the bit of information 0 and 1.
• The transistor and capacitor are paired to make a memory cell.

70. Characteristics of the Dynamic RAM
• It has short data lifetime
• Need to be refreshed continuously
• Slower as compared to SRAM
• Used as RAM
• Lesser in size
• Less expensive
• Less power consumption

71. Read Only Memory (ROM)
• ROM stands for Read Only Memory.
• This type of memory is non-volatile.
• The information is stored permanently in such memories during
manufacture
• A ROM, stores such instructions that are required to start a computer.
• ROM chips are not only used in the computer but also in other electronic
items like washing machine and microwave oven.

72. Following are the various types of ROM
• Masked ROM
• Programmable ROM
• Erasable Programmable ROM
• Electrically Erasable Programming ROM
• Flash ROM

73. Programmable ROM (PROM)
• It is a memory chip on which write operation can be performed only once.
• The data on this ROM is written permanently and cannot be erased
afterwards.
• The writing process on such ROM is called ‘Burning ROM’.
• It is mostly used in video games and electronic dictionaries.

74. Erasable Programmable ROM (EPROM)
• In such type of ROM, data can be erased or destroyed using Ultra-Violet
(UV) rays.
• facility of changing the content is available.
• facilitates the storage of data for longer terms.

75. Electrically Erasable Programmable ROM
(EEPROM)
• It is the type of ROM in which data can be erased or destroyed electrically
with the means of electric charge.
• data can be written or read at the rate of one bit per unit time which makes
it slow.

76. Flash ROM (FROM)
• It is a variation of EEPROM that uses floating gate transistors which can store data
for a longer period of time
• It is mainly used in mobile phones, digital cameras, etc.
• It is the fastest form of ROM.
• It uses continuous memory cells for storing data.
• It is of two types.
a. NAND Flash ROM
b. NOR Flash ROM

77. Secondary storage