Explain generations of computers

1. FIVE GENERATIONS OF MODERN COMPUTERS
1. Introduction
2. First Generation Computer
3. Second Generation Computer
4. Third Generation Computer
5. Fourth Generation Computer
6. Fifth Generation Computer
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2. INTRODUCTION
 Computers are appear from 1940 onwards
1. First Generation Computer(1945-1955)
2. Second Generation Computer(1957-1963)
3. Third Generation Computer(1964-1971)
4. Fourth Generation Computer(1972 onwards)
5. Fifth Generation Computer(present & future)
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3. FIRST GENERATION COMPUTER(1945-1955)
 In 1946, two engineers from University of Pennsylvania,
John Presper Eckert(1916-1995)& John W.Mauchly , built
the first digital computer using parts called vacuum
tubes.- ENIAC(Electronic Numeric Integrator &
calculator)
 It consisting of 18,000 vacuum tubes, 70,000 resistors &
5 million soldered joints, it consuming 160 KiloWatts of
electric power.
 Von Neumann designed the Electronic Discrete Variable
Automatic Computer(EDVAC) in 1947, memory can hold
storage program & data.
 The stored memory technique & conditional control
transfer allow the computer to stop at any time & then
resumed.
 Key element in Neumann architecture is CPU.
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4. FIRST GENERATION COMPUTER(1945-1955)
 It is characterized by operating instructions ,
specific task for which computer was to be used.
 Each computer had a different binary-coded
program called a Machine Language.
 It is difficult to program & limited its versatility &
speed.
 Magnetic drum for storage.
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5. SECOND GENERATION COMPUTERS(1956-1963)
 The transistor was at work in the computer by 1955.
 Magnetic core- memory, transistors led to second
generation computers were faster, more reliable more
energy than FGC.
 IBM & LARC are developed for atomic energy
laboratories to handle large amount of data.
 The machines were too costly & powerful.
 Only 2 LARC’s were installed, one is placed in Lawrence
Radiation Labs in Livermore, California( computer named
Livermore Atomic Research Computer), another one
placed in U.S. Navy Research and Development Center
in Washington D.C 5

6. SECOND GENERATION COMPUTERS(1956-1963)
 SGC replaced machine language with assembly
language , programming codes to replace long difficult
binary codes. SGC used in business universities &
government like Honeywell & IBM.
 It contained transistors in place of vacuum tubes, it also
have printers, tape, disk storage, memory, operating
system & stored programs.
 It was the stored program & programming language
that gave the flexibility to cost effective & productive for
business.
 Instructions to run a computer for specific task, different
set of instructions for different computers.
 Integrating transistors & other components into circuits
that could be placed on small chip of silicon. 6

7. THIRD GENERATION COMPUTERS(1964-1971)
 Transistors generated a great heat, which damaged
computers internal parts, quartz rock eliminated this
problem.
 Jack Kilby , an Engineer with Texas Instruments , developed
the Integrated Circuit(IC)in 1958.
 IC combined 3 electronic components onto a small silicon
disc made from quartz, Scientists fit more components on a
single chip, called a semiconductor.
 To process either scientific or non scientific applications.
 It had a large set of built-in instructions , that execute.
 Useful in scientific processing & record-keeping
applications.
 The use of OS that allow machines to run many different
programs with CPU & Computers memory. 7

8. FOURTH GENERATION COMPUTERS(1972
ONWARDS)
 Large –Scale Integration (LSI)-could fit 100s of
components onto one chip.
 1980’s Very Large Scale Integration(VLSI)- 100-1000’s of
components onto a chip.
 Ultra- Large Scale Integration(VLSI)-millions of chip.
 Increased their power efficiency & reliability,
microprocessors could be manufactured then
programmed to meet any number of demands.
 Microwaveovens, televisions & automobiles used
microprocessors.
 In the mid 1970’s computers are user friendly software
packages and also word processor & spreadsheet. 8

9. FOURTH GENERATION COMPUTERS(1972
ONWARDS)
 In the early 1980’s, arcade video games-pacman,
Home video game system-Atari 2600.
 In 1981, IBM introduced its Personal Computer for use in
homes, offices and schools.
 2 million computers used in 1981’s.
 5.5million computers used in 1982.
 Ten years later 65 million computers were used.
 Apple’s Macintosh introduced in 1984.
 Macintosh offered an OS, it allows users to move screen
icons(Graphical User Interface or GUI)instead of typing
instructions.
 Users controlled the screen cursor using a mouse.
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10. FOURTH GENERATION COMPUTERS(1972 ONWARDS)
 Smaller computers are more powerful , they could be
linked together or networked to share memory space ,
software, information & communicated with each other.
 Networked computers allowed individual computers to
form electronic co-operations.
 Using either direct wiring , called a Local Area
Network(LAN) or telephone lines.
 With the popularity of Internet and WWW & With mobile
computing, everyone can access the data from anywhere.
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11. FIFTH GENERATION COMPUTERS(PRESENT &
FUTURE)
 The example of fifth generation computer is fictional
HAL9000 from Arthur C.Clarke’s novel 2001.
 Using recent engineering advances, computers may be
able to accept spoken word instructions & imitate human
reasoning.
 Parallel processing –many CPU’s to work as one.
 Semiconductor technology – the flow of electricity with
little or no resistance, improving the speed of information
flow.
 Fifth generation computers are mega chips & Artificial
Intelligence(AI), will use super large-scale integrated
(SLSI)chips –A microprocessor millions of electronic
components in a single chip. 11

12. FIFTH GENERATION COMPUTERS(PRESENT & FUTURE)
 5th generation computers are designed to contain a large
number of processors, grouped into three major
subsystems- a knowledge base system, an inference
mechanism & an intelligent user Interface.
 The knowledge base system, has a very large store of
knowledge with a set of processors, which access & update
it.
 The inference mechanism draws reasoned conclusions
from the knowledge base. Much of its processing will be
drawing logical inferences of ‘If<condition>then<action>
variety.
 The intelligent user interface is the point of contact between
a fifth generation computers & its users, based on
communication in a large subset of a natural language.
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13. FIG. SCHEMATIC REPRESENTATION OF A FIFTH GENERATION COMPUTER
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k
knowledgebase
Inference
processor
Intelligent User Interfaces
Application
systems

14. CPU &MEMORY UNITS
1. Introduction
2. Central processing Unit(CPU)
3. Memory
4. Memory organization
5. Different types of memory
6. RAM
a. DYNAMIC RAM
b. STATIC RAM
1. ROM PROM EPROM EEPROM
2. Registers
3. Instruction set
4. Machine cycle
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15. INTRODUCTION
 Computer needs both Hardware & Software.
 Hardware Consists of the mechanical and electronic devices –
can see & touch.(i)Processing H/W (ii)Peripheral devices
 Software Consists of programs.
 The operating Systems and data the reside in the memory and
storage devices.
 Four functions
 Receive Input: Accept information from outside through various
input devices like the keyboard, mouse etc.
 Process information –perform arithmetic & logic operations
 Produce output: communicate information through output devices
like monitor, printer, etc
 Storage information: store the information like hard disk, floppy
disks. 15

16. CENTRAL PROCEESING UNIT(CPU)
 The part of the computer that executes program
instructions is known as the processor or CPU.
 The CPU consists of 3 main components
 (i)control Unit (ii)Arithmetic & Logic Unit(ALU)
(iii)Registers.
Control Unit:
All the computer’s resources are managed from the control
unit. It is the logical hub of the computer.
The instructions or instruction set , list all the operations that
the CPU can perform.
Each instruction in the instruction set is expressed in
microcode- a series of basic directions that tells the CPU
how to execute more complex operations. 16

17. ARITHMETIC LOGIC UNIT(ALU)
 It performs two types of operations arithmetic &
Logical operations.
 Arithmetic operations: Addition, Subtraction,
Multiplication, Division,& Exponent.
 Logical operations: =,≠ ,≤ ,≥, < , >.
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18. MEMORY
 Memory units are the internal storage areas in a computer.
 Memory-data storage (chips), storage- memory that exists on
tapes or disks.The term memory usually referred to as physical
memory.
 Virtual memory- expands physical memory onto a hard disk.
 Physical memory usually referred to as the main memory or the
RAM.
 Main memory hold a single byte of information .
 For example 1MB of memory can hold 1 million bytes (or
characters) of information.
 Two types of memory
 RAM
 ROM
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19. MEMORY ORGANIZATION
 Memories are characterized by their function, capacity, & response time.
 The performance of a memory system is defined by2 different measures –
access time & cycle time.
 Access time also known as response time or latency:-how quickly the memory
can respond to a read or right request.
 This time varies from about 80 nanoseconds(1 ns= one billionth (10-9) of a
second.
 The unit of information transferred between items in the hierarchy is a Block.
Blocks transferred to and from cache are known as cache lines, and units
transferred between primary & secondary memory also known as pages.
 Replacement strategy- determines which block currently in a higher level will
be removed to make a room for the new block. (FIFO,LRU)
 A request i.e satisfied is known as hit, a request that must be passed to a
lower level of the hierarchy is a miss. The percentage of requests that result in
hits determines the hit race.
 Effective Access Time(EAT)= Hit rate* cache Access time+(1-Hit rate)* main
memory access time.
 =0.98*10+0.02*100=9.8+2=11.8 ns.
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20. RAM (RANDOM ACCESS MEMORY)
 RAM- READ and WRITE memory.
 You can both write data into RAM & read data from RAM.
 KiloBytes(KB)-1024 Bytes
MegaBytes(MB)-1024 KB
GigaBytes(GB)-1024 MB
 It is volatile- it requires a steady flow of electricity to maintain
its contents, when power is turned off, data was lost.
 It can be accessed randomly.
 Two basic types of RAM
 Dynamic RAM(DRAM)
 Static RAM(SRAM)
 2 Types differ in their technology
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21. DIFFERENCE B/W DRAM & SRAM
Dynamic ram
needs to refreshed
thousands of times
per second
Static ram needs
to be refreshed
less often
Slower, less
expensive
Faster, more
expensive
Both ram are
volatile 21

22. DYNAMIC RAM(DRAM)
 Conventional DRAM: Oldest & slow DRAM.It uses the standard
memory addressing method. 1st row address sent to the memory
& then column address.
 FPM (Fast Page Mode)DRAM: FPM DRAM or Fast Page Mode
DRAM was designed to be faster than conventional types of
DRAM. As such it was the main type of DRAM used in PCs,
although it is now well out of date as it was only able to support
memory bus speeds up to about 66 MHz.
 EDO(Extended Data Out) DRAM: Extended Data Out DRAM
was a form of DRAM that provided a performance increase over
FPM DRAM. Yet this type of DRAM was still only able to operate
at speeds of up to about 66 MHz.
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23. DYNAMIC RAM(DRAM)
 BEDO DRAM: The Burst EDO DRAM was a type
of DRAM that gave improved performance of the
straight EDO DRAM. The advantage of the BEDO
DRAM type is that it could process four memory
addresses in one burst saving three clock cycles
when compared to EDO memory. This was done by
adding an on-chip address counter count the next
address.
SDRAM: Synchronous DRAM is a type of DRAM
that is much faster than previous, conventional
forms of RAM and DRAM. It operates in a
synchronous mode, synchronising with the bus
within the CPU.
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24. DYNAMIC RAM(DRAM)
 Double Data Rate SDRAM(DDR SDRAM)
 Direct Rambus DRAM(DRDRAM)
 Synchronous –link DRAM(SLDRAM)
STRENGTHS OF STATIC RAM
 Simplicity: it dono’t require external refresh cicuitary
 Speed: faster than DRAM
 Cost: Expensive
 Size: more space.
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25. ROM(READ ONLY MEMORY)
 For example , a computer with 8MB RAM , has
approximately 8 million bytes of memory that
programs can use.
 A small amount of read-only memory that hold
instructions for starting up the computer.
 A data has been prerecorded. Once data has been
written onto a ROM chip, it can’t be removed & can
only be read.
 It is non volatile.rom stores critical programs such as
computer booting , ROM used in calculators &
printers (fonts are stored in ROMs)
 Permance: any values stored in the ROM are
always there. Whether power is on or off.
 Security: ROM can’t easily be modified provides a
measure of security againt accidental content
change.
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26. PROM(PROGRAMMABLE READ ONLY
MEMORY)
 It can store a program. But once the PROM has
been used. You can’t wipe it.
 PROM’s retain their contents when the computer is
turned off.
 To write data onto PROM chip –need a special
device called a PROM programmer or a PROM
burner. This process is called burning the PROM
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• It is manufactured as blank
memory
PROM
• It is programmed during the
manufacturing process
ROM

27. EPROM(ERASABLE PROGRAMMABLE
READ-ONLY MEMORY
 It is a special type of PROM , that can be erased by
exposing it to ultraviolet light.
 The ultraviolet light clears its contents , making it
possible to reprogram the memory.
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• It can be written to only once & can’t be
erased.
PROM
• It mostly used in PC’s , they enable the
manufacturer to change contents of the
PROM. Bugs can be removed & new
version installed shortly before delivery.
EPROM

28. EEPROM(ELECTRICALLY ERASABLE
PROGRAMMABLE READ-ONLY MEMORY
 It is a special type of PROM. It can be erased by
exposing it to an electrical charge.
 EEPROM retains its contents when the power is
turned off.
 ROM,EEPROM is not as fast as RAM.
 EEPROM is similar to flash memory(flash EEPROM)
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• Data to be written or
erased one byte at a time.
EEPROM
• Data to be written or
erased in blocks.
Flash memory

29. FLASH MEMORY
 It is a special type of EEPROM. It can be erased &
reprogrammed in blocks instead of one byte at a
time.
 Many PC’s have their BIOS(BASIC INPUT
OUTPUT SYSTEM)stored on a flash memory chip
, so it can be easily updated if necessary.
 Such BIOS is called Flash BIOS.
 Flash memory also possible in modems.
 it enables the modern manufacturer to support new
protocols as they become standardized.
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30. REGISTERS
 Several additional storage locations called
registers.
 These appear in the CU & ALU & make processing
more efficient.
 It is a sort of staging area, where temporarily hold
data & instructions during processing.
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31. FACTORS AFFECTING PROCESSOR SPEED
 Registers: the size of the register is called Wordlength.
 Memory:swapping is a new technique, in which portions
of data are copied into main memory as they are
needed, swapping occurs when there is a no room in
memory for needed data.
 When one portion of program code or data copied into
memory(swap in), an equal sized portion is copied
out(swap out) to make a room.
 Clock speed: Clock Speeds are usually determined in
MHz, 1 MHz representing 1 million cycles per second, or
in GHz, 1 GHz representing 1 thousand million cycles
per second. 4.77 MHZ OR 4.77 million cycles per
second-OPERATE on first pc. Now 2GB.
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32. FACTORS AFFECTING PROCESSOR SPEED
 Clock Cycle:is a single tick or vibration of the clock & its
is the time taken to turn a transistor off & back on again.
 Bus: A collection of wires through which data is
transmitted from one part of a computer to another.
 You can think of a bus as a highway on which data
travels within a computer. When used in reference to
personal computers,
 the term bus usually refers to internal bus. This is a bus
that connects all the internal computer components to
the CPU and main memory. There's also an expansion
bus or external that enables expansion boardsto access
the CPU and memory.
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33. BUS
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34.  All buses consist of two parts -- an address busand
a data bus. The data bus transfers actual data
whereas the address bus transfers information
about where the data should go.
 The size of a bus, known as its width, is important
because it determines how much data can be
transmitted at one time.
 For example, a 16-bit bus can transmit 16 bits of
data, whereas a 32-bitbus can transmit 32 bits of
data.
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