MIS: Computers, Dr. Ashish K. Gupta

8/10/2013
1
Computers
Dr. Ashish K. GuptaDr. Ashish K. Gupta
MBBS, MS-Surgery, PGDHHM, MBA-HCA (FMS) Gold
Medalist, MAHA, PG in Quality Management & AHO,
Consultant Surgeon, Hospital Consultant,
NABH-Assessor, CMD Blue Ocean Consultants
Director Programs AHA
Study Objectives:
1. History
2. Computers- Structure & Functions
3. Computer Functions
1. Processing data
2. Data Storage
3. Data Movement:
4. Control Mechanism:
4. Computer Subunits
1. Central Processing Unit CPU
2. Main Memory
3. Input Output Units
4. Interconnections
5. Computer Speed
6. Gates & Memory Cells
7. Microchip Speed
8. Microchip
9. CPU
10. Main Memory
11. Secondary Memory
12. Input Output Devices
Saturday, August 10, 2013 drashishkgupta@gmail.com 2
(Study Duration= 1 Hour)
History
• Computers have brought about a revolution in the field of
computing as a result of technological advancement in the
field of electronics
• ‘Abacus’ the first mathematical devices used to facilitate
arithmetical computation was invented by the ancient
Chinese before the birth of Christ
• Abacus used beads strung of wires & is even today in use
First Mechanical Computer
• Also KA ‘Analytical Engine’
• Designed by Charles Babbage
• Between 1830 & 1850 marked the birth of
computer age
• It was able to perform basic arithmetical
functions
Five components of Charles
Babbage’s Analytical Engine
• A store to hold numbers
• An arithmetic unit (which he called the ‘Mill’) to
perform arithmetical operations
• A control unit to control & coordinate various
activities in the correct sequence
• An input device to transfer both numbers &
instructions into the computer
• An output device to display the results of
computation
Remarkably..
• Even today’s computers are built around the same
concepts
• Modern computers however provide three major
advantages:
– Enabling the computer to operate at electronic speed (an
electron travels 1 foot in I billionth of a second
– Providing tremendous reliability
– Making the computer a general purpose machine

8/10/2013
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History Contd..
• The first computer was KA UNIVAC (Universal Automatic
Computer) using vacuum tube circuits & was used by the US
Census Bureau in 1951. this belonged to the First Generation of
Computers
• Invention of transistor by Bell Labs USA gave birth to Second
Generation Computers which used transistors instead of
vacuum tubes. IBM 1401
• Third generation computers introduced in mid 1960s with the
invention of tiny integrated circuits on silicon chips. IBM
released its 360 series computers
• Computers with large scale ICs became available in 1969 & were
KA fourth generation computers. But there is no general
agreement on what constitutes a Fourth Generation Computer
History Contd..
• Invention of the micro-processor in 1972 changed the
computing scene dramatically
• A Microprocessor when integrated with memory & input/
output units became a micro-computer
• Micro-computer is very small in size, at the same time is very
powerful & provides a user friendly atmosphere for users to
interact with it
• The first business microcomputer KA APPLE 11 was released
in USA in 1977
History Contd..
• Recent advances in the field of artificial intelligence are being
used to design a ‘thinking computer’
• It has been tried to infuse intelligence into the computers
• These are KA Fifth generation computers
• A special feature anticipated in these computers is their ability
to respond to spoken words
ComputersComputers-- Structure & FunctionsStructure & Functions
• Structure & functions of computers are simple
• A computer is expected to perform four operations:
– Data processing
– Data storage
– Data movement
– Control
ComputerComputer
FunctionsFunctions
Data
Movement
Control
Mechanism
Data
Processing
Data
storage
Computer FunctionsComputer Functions
1. Processing data: From the point of view of a user this data
may take a variety of forms & the range of processing
requirements are very broad, but fundamentally within the
computer there are very few types of data processing
2. Data Storage: Essential for a computer. Even when the
processing is being done on the fly & the results are being
generated as the data is being fed, there is some form of
temporary storage required. Storage requirements are
therefore for short & long term

8/10/2013
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3. Data Movement: From outside world & manipulated data
back to the outside world. The movement of data can be
both to the devices directly attached to the computer i.e.
peripherals or to the remote devices. The form of movement
is KA Input, Output & when to the remote devices, data
communications
4. Control Mechanism: All of the above requires some measure
of control. Computers run several programs at the same
time, for many users at the same time. Inputs from one user
must be segregated from the inputs of others & ditto for the
outputs. This control is exercised by the instructions supplied
by the users of the computers themselves. Within the
computer there is a control unit that manages the resources
& aligns the functioning of various parts in accordance with
these instructions
Computer Subunits: HardwareComputer Subunits: Hardware
Corresponding to these
functions there are sub-
units within a computer to
accomplish these. They are;
1. Central Processing Unit
CPU
2. Main Memory
3. Input Output Units
4. Interconnections
ComputerComputer
SubunitsSubunits
Input/
Output
Inter
connections
Central
Processing
Unit
Main
Memory
Computer
Computer SpeedComputer Speed
• We have seen that computers have been increasingly
becoming faster & cheaper
• Obvious questions are:
– What is the speed of a computer?
– How is it related to the size of the computer?
• The four functions of data processing, data movement, data
storage & data control inside a digital computer are provided
by only two fundamental structures:
– Gates &
– Memory cells, interconnected to each other
Gates & Memory CellsGates & Memory Cells
• These are constructed out of simple electronic components
like:
– Resistors
– Capacitors etc.
– These are now fabricated on a single silicon chip
– Small scale integration combines thousands of these
components at a time & today a very large scale
integration can combine millions of these components on
a single chip

8/10/2013
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Gates & Memory CellsGates & Memory Cells
This means:
• Gates & memory elements can be placed much closer to each
other reducing the time electrical impulses to travel hence
increasing speed
• More & more gates & memory can be placed in the same
space increasing speed for the same size
• There is a reduction in power & cooling requirements
• The computer becomes smaller
• The interconnections become more & more reliable
Microchip SpeedMicrochip Speed
• Microchips work with an arrangement of clock speed or
frequency, in one cycle they execute one operation
• Speed is measured in hertz, i.e. cycles per second
1 Kilo Hertz= 10 3 Hertz 1000 Hertz
1 Mega Hertz= 103 Kilo Hertz 1000000 Hertz
1 Giga Hertz= 103 Mega Hertz 1000000000 Hertz
MicrochipMicrochip
• Microchip is the brain behind the computer
• Processing unit works along the Main Memory & Input Output
Unit to perform tasks that we see computers performing
• The processing unit is also KA Central Processing Unit CPU
CPUCPU
• CPU is the most important component of a computer’s
hardware & has an arithmetic logic unit (ALU) & a control
unit
• ALU performs all the arithmetical (+, x, ÷) & logical (Is A=B? Is
a given character equal to M for Male & F for Female?)
operations
• All arithmetic & logical operations are performed in the CPU
in a special storage area called registers
• The size of register is a very important consideration in
determining the speed of processing
• Register size means the amount of information that can be
held by the register at a time for processing- Larger the Faster
CPU Contd..CPU Contd..
• CPU’s processing power is measured in million instructions
per second (MIPS)
• Speed of CPU was measured in
– Milliseconds (1/1000th of a second) on first generation computers
– Micro-seconds on second generation computers (one millionth of a
second)
– Nano-seconds on third & fourth generation computers (one billionth
of a second)
– It is expected to be measured in pico-seconds (one 1000th of a nano-
second) in near future fifth generation computers.
Architecture of Computer HardwareArchitecture of Computer Hardware
Input Device Output Device
Control Unit
ALU
e.g. Keyboard,
Mouse, Mike,
Camera, Scanner,
CD/DVD Rom
CPU e.g. Printer, Display
Screen, Speakers,

8/10/2013
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CPU: Control UnitCPU: Control Unit
• Control unit in CPU controls & coordinates all operations of a CPU
• It ensures that required information is transferred between main
memory, ALU, Input devices & Output devices in required &
desired sequence
• It also contains logic circuits & storage needed for control of
multiple input output devices
• When a program begins an input operation, control unit identifies
the input devices & sets up electronic data path for the data &
instructions to enter CPU
• Subsequently control unit executes various operations in CPU in
desired manner
• Upon completion of job, control unit identifies the required
output devices & sets up data paths for supplying the output
informationto the desired output devices
Main Memory (MM)Main Memory (MM)
• MM stores a variety of critical information required for
processing by CPU
How does it store information?
• A computer works on electricity
• A binary number system that uses only two digits, namely 0 &
1 is a convenient way to represent information
• 1 represents presence of an electric impulse & 0 represents its
absence
• Information in a computer consists of data (numerical & non-
numerical) & instructions that are made up of large number of
characters like decimal numbers 0 to 9, alphabets A to Z,
arithmetic operations +, -, x, ÷ etc., relational operators etc. &
many special characters like (, . ? “ ; :) etc.
Main MemoryMain Memory
• With two binary digits we can represent four different
characters (00, 01, 11)
• With three digits we can represent eight different characters
(000, 100, 010, 001, 110, 011, 101, 111)
• Computers use eight binary digits (bits) to represent
informationinternally, allowing up to 256256 different characters
• A collection of eight bits is called a byte
• One byte is used to represent or store one character internally
• Most computers use 2 or 4 bytes to represent numbers
(positive & negative) internally
• Memory unit stores all information in memory cells, KA
memory locations, in binary digits
• Each memory location has a unique address
• Contents of a memory location are provided to the central
processing unit by referring to the address of the memory
location
• The amount of information that can be held in the main
memory is KA Memory capacity
• This capacity is measured in Kilobytes (KB)
• 1 KB stands for 103 which are approximately 1000 bytes
• A mega byte stands for 106 which are approximately one
million bytes or 1000 KB
• Earlier computers used magnetic core memory
• Modern computers use semi-conductor memory, which is
faster & cheaper than magnetic core memory
• Semi-conductor memory is also available in a small board
• This has made SC Memory more popular & attractive
• Only drawback of SC memory is that it is volatile i.e. it loses its
contents in the event of power failure. However this is not a
serious drawback & is overcome by back-up power
• SC memory is also KA RAM (Random Access Memory)
• RA means that any part of the memory can be accessed for
reading & writing
• RAM capacity is a useful indicator to compare the main memory
capacity of various computers
• Another part of main
memory is ROM (Read Only
Memory)
• ROM allows its contents to
be read only, a does not
allow users to store their
programs
• Usually ROM contains utility
programs supplied by
manufacturers

8/10/2013
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Secondary MemorySecondary Memory
• SM is essential to any computer due to its limited MM
• Three types of SM available:
1. Serial access memory: This provides only a serial access to retrieve
information stored in it
2. Random access memory: Provides a random access to retrieve
information stored in it
3. Index sequential method: The file here is accessed by certain tables that
divide the file into definite areas. The read/ write head is taken to the
beginning of the concerned area & therefore the file is accessed
sequentially
• Like a cassette tape provides serial access & LP record providing
a random access memory
• Computers use magnetic tapes to provide serial access memory
& magnetic discs to provide random access memory
Input & Output DevicesInput & Output Devices
• The input or output units of a computer system establishes
the communication between the system & its users.
• A large number of input output devices are available.
• Few devices are:
– Punched card: Most ancient input medium. A card reader is reqd.
– Terminals: Very popular input, output units. Directly connected to CPU
is used to send in information & extract information either as a print
on a paper (Hard copy terminal) or on a display screen (Soft copy
terminal)
– Key-to-tape, key-to-disk & key-to-diskette: are stand alone data entry
stations and are convenient to use
– A graphic display terminal: Displays information in both character &
graphic forms. These are extensively used for CAD/CAM (Computer
Aided Design/ Manufacture) applications
– A plotter: Is used to obtain printed copies of graphic outputs. Used by
architects & designers
– Printers: Popular output devices. Classified as line printers, dot
printers. Line printer prints one line at a time while the dot matrix
printer prints one character at one time
– Daisy Wheel printers & Letter Quality Printers: These are also
character printers, but they produce excellent quality output. Very
expensive & slow
– All the printers discussed above are impact printers as they make
physical contact with the paper while printing; a non impact printer
transfers information to paper without any physical contact. E.g. Laser
printers, Xerographic printers, Electrostatic printers
• Source data automation: This is the recent trend for data
input. The equipments used for source data automation
capture data as a by-product of a business activity thereby
completely eliminating manual input of data
– Magnetic Ink Character Recognition: Used by banking system to read
account numbers on cheques directly & to do necessary processing
– Optical Mark Recognition Devices: Can sense marks on computer
readable paper. Used in academic & testing institutions to grade
aptitude tests wher candidates mark the answers on a special sheet of
paper that are directly read by the optical mark recognition devices;
Another example if Bar Code Reader.
Questions?

MIS: Computers, Dr. Ashish K. Gupta

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