Subject: COA

Functional Units of Computer System

Prepared By:
Ms. Sheilly
Asstt . Prof.
CSE
 Digital Computer
 Digital Computer: A digital computer can be
defined as a programmable machine which
reads the binary data passed as instructions,
processes this binary data, and displays a
calculated digital output. Therefore, Digital
computers are those that work on the digital
data.
Functional Components of
Computer
Input Unit
 The input unit consists of input devices
that are attached to the computer.
 Following are some of the important
input devices which are used in a
computer −
Keyboard
Mouse
Joy Stick
Light pen
Track Ball
Scanner
Graphic Tablet
Microphone
Magnetic Ink Card Reader(MICR)
Optical Character Reader(OCR)
Bar Code Reader
Optical Mark Reader(OMR)
CPU

 Central Processing Unit (CPU)

 Once the information is entered into the

computer by the input device, the processor
processes it.

 The CPU is called the brain of the computer

because it is the control center of the  The CPU has three main
computer. components which are responsible
 It first fetches instructions from memory and for different functions –
then interprets them so as to know what is to Arithmetic Logic Unit (ALU),
be done. Control Unit (CU) and Memory
 Thereafter CPU executes or performs the
registers/Memory Unit.
required computation and then either stores
the output or displays on the output device.
Output Unit
 The output unit consists of output
devices that are attached with the
computer.

 It converts the binary data coming

from CPU to human understandable
form. The common output devices are
monitor, printer, plotter etc.

 Following are some of the important

output devices used in a computer.
Monitors
Graphic Plotter
Printer
Headphones
Speakers
Projectors
Memory Registers
 Registers are the smallest data holding
elements that are built into the processor
itself.

 Registers are the memory locations that

are directly accessible by the processor.

 The registers hold the instruction or

operands that is currently being accessed
by the CPU

 These are used to store the data which is

directly used by the processor.

 Registers can be of different sizes(16 bit,

32 bit, 64 bit and so on) and each register
inside the CPU has a specific function like
storing data, storing an instruction, storing
address of a location in memory etc.
Memory
 Memory attached to the CPU is used  When a program is executed, it’s
for storage of data and instructions data is copied to the internal
and is called internal memory. memory and is stored in the
memory till the end of the
 The internal memory is divided into
many storage locations, each of which
execution.
can store data or instructions. Each
memory location is of the same size
 The internal memory is also called
and has an address. the Primary memory or Main
memory. This memory is also
 With the help of the address, the called as RAM, i.e. Random
computer can read any memory Access Memory.
location easily without having to
search the entire memory.
Difference between Memory and
Registers
 Registers are
the high-
speed accessible
storage elements.
 Processor can access
registers faster than
the main memory.
System Bus
 The system bus is a pathway composed
of cables and connectors used to carry
data between a computer microprocessor
and the main memory.
 A bus is a communication system that
transfers data between components inside
a computer, or between computers.
 This expression covers all related
hardware components (wire, optical
fiber, etc.) and software, including
communication protocols.
 It combines the functions of a data
bus to carry information, an address bus
to determine where it should be sent,
and a control bus to determine its
operation or carry signals from processor
to other components.
Memory
Memory is primarily of three types −
 Cache Memory
 Primary Memory/Main Memory
 Secondary Memory
Main Memory
 The main memory acts as the  The integrated circuits for the main
central storage unit in a memory are classified into two major
units:
computer system.  RAM (Random Access Memory)
integrated circuit chips
 It is a relatively large and fast  ROM (Read Only Memory)
memory which is used to store integrated circuit chips
programs and data during the  RAM is referred to as volatile
run time operations. memory and is lost when the power
is turned off whereas ROM in non-
 The primary technology used volatile and the contents are retained
for the main memory is based even after the power is switched off.
For ex-ROM stores the instruction for
on semiconductor integrated the PC to start up when its turned on
circuits. again.
 Secondary Memory
 This type of memory is also
known as external memory or
non-volatile. It is slower than the
main memory.

 These are used for storing

data/information permanently.

 The contents of secondary

memories are first transferred to
the main memory, and then the
CPU can access it.

 For example, disk, CD-ROM,

DVD, etc.
 Cache Memory
 Cache memory is a very high speed semiconductor memory which can speed up the CPU.

 It acts as a buffer between the CPU and the main memory.

 It is used by CPU(which automatically turns to cache memory in search of data) to

reduce the average cost(time/energy) to access data from the main memory as RAM is
slower and farther away form CPU.

 It is used to hold those parts of data and program which are most frequently used by the
CPU.

 The parts of data and programs are transferred from the disk to cache memory by the
operating system, from where the CPU can access them

 It is the fastest memory in a computer, and is typically integrated onto the motherboard
and directly embedded in the processor or main random access memory (RAM).
 Cache Memory
 Advantages:  Disadvantages:
 Cache memory is faster  Cache memory has
than main memory. limited capacity.
 It consumes less access  It is very expensive.
time as compared to main
memory.
 It stores the program that
can be executed within a
short period of time.
 It stores data for
temporary use.
Switched Mode Power Supply(SMPS)

 1.Switch mode power supplies  3.Basically, it is a device in which

(SMPSs) are used in a range of energy conversion and regulation
applications as an efficient and is provided by power
effective source of power. semiconductors that are
continuously switching “on” and
 2.SMPS is a power supply that “off” with high frequency.
uses a switching regulator to
control and stabilize the output  4.SMPS is defined as when the
voltage by switching the load power supply is involved with the
current on and off. These power switching regulator to change the
supplies offer a greater power electrical power from one form to
conversion and reduce the overall another form with required
power loss. characteristics is called SMPS.
 Motherboard
 The motherboard serves as a  Features of Motherboard:
single platform to connect all
of the parts of a computer
 Motherboard varies greatly in
supporting various types of
together.
components.
 Motherboard supports a single
 It connects the CPU, memory, type of CPU and few types of
hard drives, optical drives, memories.
video card, sound card, and  Video cards, hard disks, sound
other ports and expansion cards have to be compatible with
cards directly or via cables. the motherboard to function
properly.
 Motherboards, cases, and power
 It can be considered as the
supplies must be compatible to
backbone of a computer. work properly together.
 Computer Ports
A port has the following characteristics − PS/2 Port
 External devices are connected to a computer  Used for old computer keyboard
using cables and ports.
 Ports are slots on the motherboard into which a and mouse.
cable of external device is plugged in.  Also called mouse port.
 Examples of external devices attached via
 Most of the old computers provide
ports are the mouse, keyboard, monitor,
microphone, speakers, etc. two PS/2 port, each for the mouse
and keyboard.
 Various Ports of computer are:
 IEEE 1284-compliant Centronics
Serial Port
 Used for external modems and older computer port.
mouse
 Two versions: 9 pin, 25 pin model
 Data travels at 115 kilobits per second
Parallel Port
 Used for scanners and printers.
 Also called printer port.
 25 pin model.
 IEEE 1284-compliant Centronics port.
Firewire Port
 Transfers large amount of data at very fast speed.
 Connects camcorders and video equipment to the computer.
 Data travels at 400 to 800 megabits per seconds.
 Invented by Apple.
 It has three variants: 4-Pin FireWire 400 connector, 6-Pin FireWire 400 connector, and 9-Pin FireWire 800 connector.

Modem Port
 Connects a PC's modem to the telephone network.
 Ethernet Port
 Connects to a network and high speed Internet.
 Connects the network cable to a computer.
 This port resides on an Ethernet Card.
 Data travels at 10 megabits to 1000 megabits per seconds depending upon the network bandwidth.

Game Port
 Connect a joystick to a PC
 Now replaced by USB
 Digital Video Interface, DVI port
 Connects Flat panel LCD monitor to the computer's high-end video graphic cards.
 Very popular among video card manufacturers.
 Sockets
 Sockets connect the microphone and speakers to the sound card of the computer.
Universal Serial Bus (or USB) Port

 It can connect all kinds of external USB devices

such as external hard disk, printer, scanner, mouse,
keyboard, etc.
 It was introduced in 1997.
 Most of the computers provide two USB ports as
minimum.
 Data travels at 12 megabits per seconds.
 USB compliant devices can get power from a USB
port.

VGA Port
 Connects monitor to a computer's video card.
 It has 15 holes.
 Similar to the serial port connector. However,
serial port connector has pins, VGA port has holes.

Power Connector
 Three-pronged plug.
 Connects to the computer's power cable that plugs
into a power bar or wall socket.
 Computer Interfaces
 In computing, an interface is a There are five main types
shared boundary across which two
or more separate components of of user interface:
a computer system exchange  command line (CLI)
information. The exchange can be  graphical user interface
between software,
computer hardware, peripheral (GUI)
devices, humans, and  menu driven (mdi)
combinations of these.
 form based (fbi)
 User interface - The features of a  natural language (NLI)
computer system which allows the
user to interact with it.
 Command Line Interface
 It involves the computer
responding to commands
typed by the operator. This
type of interface has the
drawback that it requires the
operator to remember a
range of different commands
and is not ideal for novice
users.
 GUI
 Graphical user interfaces
(GUI) are sometimes also
referred to as WIMP
because they
use Windows, Icons, Menus
and Pointers. Operators use
a pointing device (such as a
mouse, touchpad or
trackball) to control a
pointer on the screen which
then interacts with other on-
screen elements.
 Menu Driven Interface
 A menu driven interface is
commonly used on cash
machines (also known as
automated teller machines
(ATM's), ticket machines and
information kiosks (for example
in a museum).

 They provide a simple and easy

to use interface comprised of a
series of menus and sub-menus
which the user accesses by
pressing buttons, often on a
touch-screen device.
 Form Based Interface
 A form-based interface uses
text-boxes, drop-down menus,
text areas, check boxes, radio
boxes and buttons to create an
electronic form which a user
completes in order to enter data
into a system.

 This is commonly used on

websites to gather data from a
user, or in call centres to allow
operators to quickly enter
information gathered over the
phone.
 Natural Language Interace
 A natural language  An Example of this type of
interface is a spoken interface is Voice
interface where the user Recognition. This is the kind
of interface used by the
interacts with the
popular iPhone application
computer by talking to it. called Siri
Sometimes referred to as
a 'conversational
interface', this interface
simulates having a
conversation with a
computer.
 Expansion Cards
 An expansion card is an  Examples: sound cards,
electronic card/board that is video graphics cards,
used to add extra network cards and so on.
functionality to a computer.
It is inserted into an expansion  Expansion cards are also
slot on the motherboard of a known as add-on cards or
computer. interface cards.
 All expansion cards are used
to enhance the quality of their  The basic purpose of
specific function. For
expansion cards is to
example, video graphics cards
enhance the existing abilities
are used to enhance the video
quality on a computer. of the motherboard.
 Types of Expansion Cards
•Sound cards:
Sound cards expand the sound
capabilities of a PC. ...
•Video cards: Video cards can
increase the overall
performance of a system,
depending upon the card that is
installed. ...
•Network cards. ...
•Serial and parallel cards. ...
•USB cards. ...
•FireWire cards. ...
•Storage cards. ...
Modem cards
 Ribbon Cables
 A ribbon cable is a flat, thin cable
composed of multiple small-grade
cables placed parallel to each other.

 With each core situated side by side,

they form a wide-flat cable
resembling a piece of ribbon, hence
its name.

 Ribbon cables are usually used

as interconnects for internal
peripherals in computers, such as
hard drives, CD drives, and floppy
drives. On some older computer
systems they were also used
for external connections.
 Memory chip
 A memory chip is an integrated circuit
made out of millions of capacitors and
transistors that can store data or can be
used to process code.
 Memory chips can
hold memory either temporarily
through random
access memory (RAM), or
permanently through read
only memory (ROM).
 Memory chips are semiconductor
devices used as internal storage areas
within a computer.
 In a semiconductor memory chip, each
bit of binary data is stored in a tiny
circuit called a memory cell consisting
of one to several transistors.
Processor
Thank
You