This document provides an introduction to the basic components of a computer system. It defines key terms like peripheral devices, input devices, output devices, and the system unit. It describes the basic operations of fetching/inputting, storing, executing/processing, outputting, and controlling that all computer systems perform. It explains the central processing unit (CPU) and its main components - the control unit, arithmetic logic unit, and memory unit. It also discusses other important components like buses, computer memory, ports, and different types of memory like primary/internal memory and secondary/external auxiliary memory.

1. INTRODUCTION TO
COMPUTER
Lecture #5

2. Components of a computer
Unit 2

3. Some common terms
 What is a computersystem?
 A computer along with a number of components attached to
it is known as a computer system.
 What areperipheraldevices?
 The devices that are attached with a system unit under the
control of CPU are called peripheral devices.
 Defineinput devices.
 Input devices are used to enter data or instructions into a
computer. e.g. keyboard, mouse, mice, scanner, light pen
etc.

4. Some common terms
 Defineoutput devices.
 Output devices give out the results to the user. They
show results and outputs. e.g. monitor, printer,
speaker etc.
 What is the‘systemunit’?
 It is the main unit of a computer system. It enables
various parts of a computer system to work
together. It contains CPU or microprocessor,
magnetic memory, semiconductor memory and disc
drives etc

5. operations performed by any computer
system
 All computer systems perform the following five basic
operations
 Fetching/Inputting: Receive data and instructions for the
system.
 Storing: Stores data and instructions to be used for
processing.
 Executing/Processing: Executes the instructions to
process data.
 Outputting: Transfer the results in a form usable by
humans or other machines.
 Controlling: Directing the manner and sequence in

6. CPU
 The Central Processing Unit (CPU) is the
brain of a computer.
 It controls the entire operations of a
computer system and executes
instructions given to it.
 It is here where raw data is transformed
into meaningful information.

7. A typical CPU performs the following
basic functions.
 Inte rpre ts data and instructio ns.
 Ge ne rate s co ntro lsig nals.
 Pe rfo rm arithm e tic and lo g ic o pe ratio ns.
 Pro duce s addre ss bits ne e de d by m e m o ry.

8. Components of CPU
 CPU chip consists of mainly three
Components
 Control Unit (CU)
 Arithmetic & Logic Unit (ALU)
 MemoryUnit (MU)

9. Control Unit (CU)
 Control Unit is the most important part of the
CPU as it manages all the resources of a
computer system.
 It works like a traffic cop directing flow of data
within a computer system. I
 t comprises of registers which function as
temporary storage devices inside it.
 It fetches instructions from RAM and stores
them in the registers and then transfers them to

10. Arithmetic & Logic Unit
(ALU)
 ALU consists of a number of adder and
logic gates.
 It performs all the arithmetic and logic
operations that take place in a computer.
 Arithmetic operations are addition,
subtraction, multiplication etc.
 Logic operations are comparison
operations, AND, OR, NOT etc.

11. Memory Unit (MU)
 A CPU has small and temporary memory
locations called registers.
 Data currently being processed is stored in
these registers.
 There are fourteen basic types of registers.

12. Bus
 A bus is a collection of electronic wires
through which data is transmitted from one
part of a computer to another.
 There are three types of buses in a
computer; data bus, address bus and
control bus.

13. Data Bus
 The data bus is an electrical path through
which data can travel between the
computers central processing unit, memory
and peripherals.
 The number of wires affects the speed at
which data travels between different
components.
 Each channel in data bus can travel one bit
of data a time. Hence a 16 bit data bus can

14. Address Bus
 The address bus is an electrical path that
connects CPU with memory.
 It is used to identify particular locations in
memory where data is stored.
 The number of wires in address bus tells the
maximum number of memory addresses. For
example 8 bit data is enough to represent 28
=
256 different values.
 Thus 8 bit address could address 256 bytes of

15. Control Bus
 The control unit controls the activities of all
the units of a computer.
 The function of control bus is sto carry the
control signals generated by the control
Unit.
 For example one line of the control bus is
used to indicate whether the CPU is
currently reading from or writing to the
main memory.

16. Computermemory
 Memory is the storage device inside the
computer where data and programs are
stored.
 The basic type of memory is set of chips
located on the motherboard so that data
can travel quickly between CPU and other
devices.
 The other is the external memory that uses
tapes and disks to store information.

17. Types Of Memory
 There are two basic types of memory
inside the computer system.
 Primary/InternalMainMemory
 Secondary/External AuxiliaryMemory

18. Primary /Internal Main
Memory
 Main memory of a computer is its internal
memory also called primary memory.
 Generally the main memory is on
semiconductor chips housed on motherboard.
 Main memory is very fast and it is directly
accessible by the CPU.
 There are two types of main memory Read
Only Memory (ROM) and Random Access
Memory (RAM).

19. Read Only Memory (ROM)
 It is a permanent memory of a computer. It
handles many important tasks.
 One of these tasks is to provide instructions
to the CPU during start up or booting
process.
 Another important role of ROM is to
generate characters when a key is
depressed.
 It is a nonvolatile memory i.e. the

20. RandomAccess Memory
(RAM)
 Ram is known as the working memory of
the computer as every program is loaded
into it while execution.
 This memory is directly accessed by the
computer.
 It is fast but volatile memory as it loses its
contents when computer is turned off or
electricity fails.

21. Secondary/External Auxiliary Memory
 Secondary storage devices are physically
separate but connected directly to the
motherboard through a cable.
 Unlike primary memory it is the slowest but
permanent memory as it retains its contents
when computer is switched off or electricity fails.
 Its contents are not directly accessed therefore,
its contents must be loaded into RAM while
execution.
 Secondary storage devices include magnetic

22. ComputerPorts
 A port is a socket or interface in a computer that is
used to plug-in different devices.
 Most of the computers have various ports. Internally,
there are several ports for connecting disk drives,
display controllers and keyboards.
 Externally computers have ports for connecting
modems, printers, scanners and other peripheral
devices.
 Generally, there are two main types of ports (Serial
Ports and Parallel Ports) but there is another type of
port known as USB port.

23. Serial Port
 A serial port is an interface through which only one
bit can be transferred at a time.
 A serial port has 9 or 25 pins and it is also known
as male connector.
 A serial port is general purpose interface that can
be used for almost any type of devices including,
Modem, mice and printers.
 In personal computers serial ports are generally
designated as COM1, COM2 and COM3 etc.

24. Parallel Port
 A parallel port is an interface through which more than
one bit at a time.
 A parallel port has 8, 16 or 32 channels or wires and it is
also known as female connector.
 Each channel carries one bit of information, so the
amount of information to be transmitted from parallel
ports depends on the number of channels present in
them.
 It is the kind of port used to connect tape drives, CD-
ROMs, extra hard disks and most of the printers.
 In personal computers parallel ports are generally

25. USBPort
 USB port is a standard cable connection
interface on personal computers.
 USB ports allow electronic devices to be
connected via cables to a computer.
 USB ports can also supply electric power
across the cable to devices without their
own power source.