This file contains complete information about computer Architecture. 1. What is a computer. 2. Types of computers 3. Block Diagram of Computer. 4 . Processor, Memory 5. Computer Generati

1. Computer Architecture
Created By: Md Shabbir

2. What is a computer
• A computer is a machine that can be instructed to carry out
sequences of arithmetic or logical operations automatically
via computer programming.
• Modern computers have the ability to follow generalized sets of
operations, called programs. These programs enable computers to
perform an extremely wide range of tasks.

3. Digital , Analog Computer &hybrid Computer
• The basic difference between Analog and Digital computers is the
type of data they process. Analog computers process analog, i.e.
continuously varying, data. Digital computer process data which is
binary, i.e. in the form of 0 and 1.
• Hybrid computers are computers that exhibit features of
analog computers and digital computers. The digital component
normally serves as the controller and provides logical and numerical
operations, while the analog component often serves as a solver of
differential equations and other mathematically complex equations.

4. Different types of computers
S.No. Type Specifications
1 PC (Personal Computer)
It is a single user computer system having
moderately powerful microprocessor
2 Workstation
It is also a single user computer system,
similar to personal computer however has a
more powerful microprocessor.
3 Mini Computer
It is a multi-user computer system, capable
of supporting hundreds of users
simultaneously.
4 Main Frame
It is a multi-user computer system, capable
of supporting hundreds of users
simultaneously. Software technology is
different from minicomputer.
5 Supercomputer
It is an extremely fast computer, which can
execute hundreds of millions of instructions
per second.

5. Personal Computer
A PC can be defined as a small, relatively inexpensive
computer designed for an individual user.
PCs are based on the microprocessor technology that
enables manufacturers to put an entire CPU on one chip.
Businesses use personal computers for word processing,
accounting, desktop publishing, and for running
spreadsheet and database management applications. At
home, the most popular use for personal computers is
playing games and surfing the Internet.
Although personal computers are designed as single-user
systems, these systems are normally linked together to
form a network.

6. Workstations
Workstation is a computer used for engineering
applications (CAD/CAM), desktop publishing, software
development, and other such types of applications which
require a moderate amount of computing power and
relatively high quality graphics capabilities.
Workstations generally come with a large, high-resolution
graphics screen, large amount of RAM, inbuilt network
support, and a graphical user interface. Most workstations
also have mass storage device such as a disk drive, but a
special type of workstation, called diskless workstation,
comes without a disk drive.
Common operating systems for workstations are UNIX
and Windows NT. Like PC, workstations are also single-
user computers like PC but are typically linked together to
form a local-area network, although they can also be used
as stand-alone systems.

7. Mini Computer
Minicomputers are mainly multi-users systems where more
than one user can work simultaneously.
Mini computer examples: IBM’s AS/400e, Honeywell200.
Used for database management
Used for Business Transactions
Used for scientific computations
File handling & Engineering Computations

8. Mainframe Computers
Mainframe is very large in size and is an expensive
computer capable of supporting hundreds or even
thousands of users simultaneously. Mainframe executes
many programs concurrently and supports many
simultaneous execution of programs.
Used in scientific research, consumer statistics, and census
data, because it is capable to execute multiple complex
programs concurrently at the ultra speed.
Today, most eminent vendors of mainframe computers are
IBM, Hitachi, Amdahl, and Unisys. Examples are IBM zSeries,
System z9 and System z10 servers

9. Super Computers
Supercomputers are one of the fastest computers
currently available. Supercomputers are very expensive
and are employed for specialized applications that require
immense amount of mathematical calculations (number
crunching).
For example, weather forecasting, scientific simulations,
(animated) graphics, fluid dynamic calculations, nuclear energy
research, electronic design, and analysis of geological data (e.g.
in petrochemical prospecting).

10. Basic Blocks of Computer System
Mainly computer system consists of Four parts, that are
• central processing unit (CPU),
• Input Devices,
• Output Devices.
• Memory
The Central Processing Unit (CPU) is divided into three parts again:
• arithmetic logic unit (ALU)
• control unit (CU).
• The set of instruction is in the form of raw data.

11. The data is entered through input devices such as the
keyboard, mouse, etc. This set of instruction is processed
by the CPU after getting the input by the user, and then
the computer system produces the output. The computer
can show the output with the help of output devices to the
user, such as monitor, printer, etc.

12. • A large amount of data is stored in the computer memory with the
help of primary and secondary storage devices.
• The CPU is like the heart/brain of the computer. The user does not
get the desired output, without the necessary option taken by the
CPU.
• The Central processing unit (CPU) is responsible for the processing of
all the instructions which are given by the user to the computer
system.
•

13. Central Processing Unit (CPU)
The control unit (CU)
• controls all the activities or operations which are
performed inside the computer system.
• It receives instructions or information directly from
the main memory of the computer.
• When the control unit receives an instruction set or
information, it converts the instruction set to control
signals then;
• these signals are sent to the central processor for
further processing. The control unit understands
which operation to execute, accurately, and in
which order.
Arithmetic and Logical Unit
It is the combinational digital electronic circuit that can
perform arithmetic operations on integer binary
numbers. It presents the arithmetic and logical
operation.

14. What is register memory
• Register memory is the smallest and fastest memory in a computer. It
is located in the CPU in the form of registers
• A register temporarily holds frequently used data, instructions, and
memory address that are to be used by CPU. They hold instructions
that are currently processed by the CPU.
• Registers hold a small amount of data around 32 bits to 64 bits. The
speed of a CPU depends on the number and size (no. of bits) of
registers that are built into the CPU.

15. Different types of registers
• Data Register: It is a 16-bit register, which is used to store operands (variables) to
be operated by the processor. It temporarily stores data, which is being
transmitted to or received from a peripheral device.
• Program Counter (PC): It holds the address of the memory location of the next
instruction, which is to be fetched after the current instruction is completed. So,
it is used to maintain the path of execution of the different programs and thus
executes the programs one by one, when the previous instruction gets
completed.
• Instructor Register: It is a 16-bit register. It stores the instruction which is fetched
from the main memory. So, it is used to hold instruction codes, which are to be
executed. The Control Unit takes instruction from Instructor Register, then
decodes and executes it.
• Accumulator Register: It is a 16-bit register, which is used to store the results
produced by the system. For example, the results generated by CPU after the
processing are stored in the AC register.

16. Main Components of a Computer
• These are mainly five components of the computer system.
• Processor.
• Main Memory.
• Secondary Memory.
• Input Devices.
• Output Devices.

17. Components of a Computer

18. Processor
The processor is an electric circuitry within the computer system. The Central
processing unit is the central processor or main processor of the computer system.
The processor carries out the instructions of the computer program with the help
of basic arithmetic and logic, input/output operations.
Main Memory
The Random Access Memory is the main memory of the computer system, which is
known as RAM. The main memory can store the operating system software,
application software, and other information. The Ram is one of the fastest
memory, and it allows the data to be readable and writeable. Main memory is
where programs and data are kept when the processor is actively using them.
When programs and data become active, they are copied from secondary memory
into main memory where the processor can interact with them. A copy remains in
secondary memory.

19. Secondary memory
We can store the data and programs on a long-term basis in the secondary memory. The
hard disks and the optical disks are the common secondary devices. It is slow and cheap
memory as compare to primary memory. This memory is not connected to the processor
directly.
It has a large capacity to store the data. The hard disk has a capacity of 500 gigabytes. The
data and programs on the hard disk are organized into files, and the file is the collection of
data on the disk. The secondary storage is not directly accessed by the CPU; that’s why it is
different from the primary storage.
The hard disk is about 100 times the capacity of the main memory. The main difference
between primary and secondary storage is speed and capacity. There are several large
blocks of data which are copied from the hard disk into the main memory.

20. Input Devices
• The user provides the set of instruction or information to the
computer system with the help of input devices such as the keyboard,
mouse, scanner, etc. The data representation to the computer system
is in the form of binary language after that the processor processes
the converted data. The input unit implements the data which is
instructed by the user to the system.
• We can enter the data from the outside world into the primary
storage as the input through input devices. The input devices are the
medium of communication between the outside world and the
computer system.

21. Output Devices
• The output devices produce or generate the desired result according to our
input, such as a printer, monitor, etc. These devices convert the data into a
human-readable form from binary code.
• The computer system is linked or connected to the outside world with the
help of output devices. The primary examples of output devices are a
printer, projector, etc. These devices have various features which are given
below:
• These devices receive or accept the data in the binary form.
• The output devices convert the binary code into the human-readable form.
• These devices produce the converted result and show to the user.

22. Fetch Execute &Decode
• The fetch execute cycle is the basic operation (instruction) cycle of a
computer (also known as the fetch decode execute cycle).
• During the fetch execute cycle, the computer retrieves a program
instruction from its memory. It then establishes and carries out the
actions that are required for that instruction.
• The cycle of fetching, decoding, and executing an instruction is
continually repeated by the CPU whilst the computer is turned on.

23. Fetch cycle
• The Program Counter contains the address of the memory location
that has the next instruction which has to be fetched
• This Address is copied from the Program Counter to the MAR
• From there it travels on the Address bus to the RAM
• The contents in the memory location move via the data bus to the
memory data register and then to the Instruction Register. PC is
incremented by one.
• The instruction is finally decoded and executed.

24. Computer Generations ----Ist Generation
• The period of first generation was from 1946-1959. The computers of
first generation used vacuum tubes as the basic components for
memory and circuitry for CPU (Central Processing Unit). These tubes,
like electric bulbs, produced a lot of heat and the installations used to
fuse frequently. Therefore, they were very expensive and only large
organizations were able to afford it.
• In this generation, mainly batch processing operating system was
used. Punch cards, paper tape, and magnetic tape was used as input
and output devices. The computers in this generation used machine
code as the programming language.

25. Computer Generations --1st
• The main features of the first generation are −
• Vacuum tube technology
• Unreliable
• Supported machine language only
• Very costly
• Generated a lot of heat
• Slow input and output devices
• Huge size
• Need of AC
• Non-portable
• Consumed a lot of electricity

26. • Some computers were −
• ENIAC
• EDVAC
• UNIVAC

27. Computer Generation 2nd
• The period of second generation was from 1959-1965. In this
generation, transistors were used that were cheaper, consumed less
power, more compact in size, more reliable and faster than the first
generation machines made of vacuum tubes. In this generation,
magnetic cores were used as the primary memory and magnetic tape
and magnetic disks as secondary storage devices.
• In this generation, assembly language and high-level programming
languages like FORTRAN, COBOL were used. The computers used
batch processing and multiprogramming operating system.

28. • The main features of second generation are −
• Use of transistors
• Reliable in comparison to first generation computers
• Smaller size as compared to first generation computers
• Generated less heat as compared to first generation computers
• Consumed less electricity as compared to first generation computers
• Faster than first generation computers
• Still very costly
• AC required
• Supported machine and assembly languages

29. Some computers of this generation were −
IBM 1620
IBM 7094
CDC 1604
CDC 3600
UNIVAC 1108

30. 3rd Generation
• The period of third generation was from 1965-1971. The computers of third
generation used Integrated Circuits (ICs) in place of transistors. A single IC
has many transistors, resistors, and capacitors along with the associated
circuitry.
• The IC was invented by Jack Kilby. This development made computers
smaller in size, reliable, and efficient. In this generation remote processing,
time-sharing, multiprogramming operating system were used. High-level
languages (FORTRAN-II TO IV, COBOL, PASCAL PL/1, BASIC, ALGOL-68 etc.)
were used during this generation.

31. • The main features of third generation are −
• IC used
• More reliable in comparison to previous two generations
• Smaller size
• Generated less heat
• Faster
• Lesser maintenance
• Costly
• AC required
• Consumed lesser electricity
• Supported high-level language
•

32. • Some computers of this generation were −
• IBM-360 series
• Honeywell-6000 series
• PDP (Personal Data Processor)
• IBM-370/168
• TDC-316

33. 4th Generation
• The period of fourth generation was from 1971-1980. Computers of
fourth generation used Very Large Scale Integrated (VLSI) circuits. VLSI
circuits having about 5000 transistors and other circuit elements with
their associated circuits on a single chip made it possible to have
microcomputers of fourth generation.
• Fourth generation computers became more powerful, compact,
reliable, and affordable. As a result, it gave rise to Personal Computer
(PC) revolution. In this generation, time sharing, real time networks,
distributed operating system were used. All the high-level languages
like C, C++, DBASE etc., were used in this generation.

34. 4th Generation
• The period of fourth generation was from 1971-1980. Computers of
fourth generation used Very Large Scale Integrated (VLSI) circuits. VLSI
circuits having about 5000 transistors and other circuit elements with
their associated circuits on a single chip made it possible to have
microcomputers of fourth generation.
• Fourth generation computers became more powerful, compact,
reliable, and affordable. As a result, it gave rise to Personal Computer
(PC) revolution. In this generation, time sharing, real time networks,
distributed operating system were used. All the high-level languages
like C, C++, DBASE etc., were used in this generation.

35. • The main features of fourth generation are −
• VLSI technology used
• Very cheap
• Portable and reliable
• Use of PCs
• Very small size
• Pipeline processing
• No AC required
• Concept of internet was introduced
• Great developments in the fields of networks
• Computers became easily available

36. • Some computers of this generation were −
• DEC 10
• STAR 1000
• PDP 11
• CRAY-1(Super Computer)
• CRAY-X-MP(Super Computer)

37. 5th Generation
• The period of fifth generation is 1980-till date. In the fifth generation,
VLSI technology became ULSI (Ultra Large Scale Integration)
technology, resulting in the production of microprocessor chips
having ten million electronic components.
• This generation is based on parallel processing hardware and AI
(Artificial Intelligence) software. AI is an emerging branch in computer
science, which interprets the means and method of making
computers think like human beings. All the high-level languages like C
and C++, Java, .Net etc., are used in this generation.

38. • The main features of fifth generation are −
• ULSI technology
• Development of true artificial intelligence
• Development of Natural language processing
• Advancement in Parallel Processing
• Advancement in Superconductor technology
• More user-friendly interfaces with multimedia features
• Availability of very powerful and compact computers at cheaper rates

39. • Some computer types of this generation are −
• Desktop
• Laptop
• NoteBook
• UltraBook
• ChromeBook
•

40. • Computer Architecture
• Computer Architecture is a blueprint for design and implementation
of a computer system. It provides the functional details and behavior
of a computer system and comes before computer organization.
Computer architecture deals with 'What to do?'
• Computer Organization
• Computer Organization is how operational parts of a computer
system are linked together. It implements the provided computer
architecture. Computer organization deals with 'How to do?'