Introduction
to Computers
Basic Components
What
Is a Computer?
machine for processing data
raw
data given as input
output is information
what is the
difference?
extracting
desired information from data
what
is the information required?
how
should it be found from the given data?
specified
by the user
What
Is Programming?
information
extracted by performing operations on data
operations to be performed specified by a sequence of instructions,
called program
a
few basic instructions are available
task
of finding an appropriate sequence of basic instructions to get desired output
is programming
What
Is Utilization?
computer is a tool
unless
used for some purpose, by itself, it does not achieve anything
use
of a computer in different domains
originally
intended only for numerical calculations in science and engineering
also the
main emphasis of this course
commercial
applications now dominate
Block
Diagram of a Computer
CPU
cpu
stands for central processing unit
heart
(and/ or brain) of the computer
controls
functioning of all components
ALU
, arithmetic-logic unit which performs arithmetic and other operations
instruction
decoder which decodes what operation is to be performed on what data and where
the result should be sent
program
counter decides the next instruction
Main
Memory
main
memory stores all instructions and data
contains
many locations, each having an integer address
no
distinction between instruction and data
location
accessed directly using its address, called random access memory (RAM)
data
access is very fast (nanoseconds)
all
data is lost when power is switched off
Data
Representation
all
data and instructions are stored in bits
bits is
short form of binary digit 0 or 1
easy to
implement as an electronic switch
each
location typically contains 32 bits
number of
locations typically > 10 million
data
and instructions encoded in bits
all
operations reduced to operations on bits
may
vary from one computer to another
Main
Memory
Peripherals
all
other components are called peripherals
peripherals
are external devices which allow users to interact with a computer
controlled
by the CPU
hard
disk or secondary memory
stores data
in permanent form
keyboard
allows users
to enter data in the computer
Peripherals
visual
display unit (VDU)
displays
data on a screen
floppy
disk
stores data
in portable form
printers
print data
on paper
network
connections
connect to
other computers
Functioning of a Computer
program
is stored in main memory
CPU
reads instruction to be executed from location specified by program counter
instruction
contains addresses of locations containing data and the result
CPU
decodes and executes instruction
program
counter updated to next instruction
continues
till a special HALT instruction
Operating
System
operating
system (OS) is a program permanently resident in main memory
controls
execution of all other programs
controls
input-output from peripheral devices
acts
as interface between users and machine
allows
sharing of machine resources
many
standard OS available
unix, linux,
windows, dos etc
Summary
basic
idea of computers and programming
main
components of a computer
CPU and main
memory
peripherals
hard disk,
keyboard, VDU, printer etc
basic
functioning of a computer
role
of an operating system