introduction to computers and component

1. Ms. Yagni Desai

2.  Computer architecture refers to those
attributes of a system visible to a
programmer.
 Those attributes that have a direct impact on
the logical execution of a program.
 The attributes:
◦ Instruction set,
◦ The number of bits used to represent various data
types (e.g., numbers, characters),
◦ I/O mechanisms,
◦ Techniques for addressing memory
 Eg.
◦ It is an architectural design issue whether a
computer will have a multiply instruction.
Ms. Yagni Desai

3.  Computer organization refers to the
operational units and their interconnections
that realize the architectural specifications.
 Those hardware details transparent to the
programmer.
 The attributes:
◦ Control signals
◦ Interfaces between the computer and peripherals
◦ The memory technology used
 Eg.
◦ It is an organizational issue whether that instruction
will be implemented by a special multiply unit or by
a mechanism that makes repeated use of the add
unit of the system.
Ms. Yagni Desai

4.  Structure: The way in which the components
are interrelated.
 Function: The operation of each individual
component as part of the structure.
 Data Processing
 Data storage
 Data movement
 Control
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6.  Data are received from or delivered to a
device that is directly connected to the
computer, the process is known as input–
output (I/O), and the device is referred to as a
peripheral.
 Data are moved over longer distances, to or
from a remote device, the process is known
as data communications.
Ms. Yagni Desai

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8.  All of computers linkages to the external
environment can be classified as peripheral
devices or communication lines.
Ms. Yagni Desai

9.  Central processing unit (CPU): Controls the
operation of the computer and performs its
data processing functions; often simply
referred to as processor.
 Main memory: Stores data.
 I/O: Moves data between the computer and
its external environment.
 System interconnection: Some mechanism
that provides for communication among CPU,
main memory, and I/O.
◦ Eg. system bus, consisting of a number of
conducting wires to which all the other
components attach.
Ms. Yagni Desai

10. Ms. Yagni Desai

11.  CPU’s major structural components are:
 Control unit: Controls the operation of the
CPU and hence the computer.
 Arithmetic and logic unit (ALU): Performs the
computer’s data processing functions.
 Registers: Provides storage internal to the
CPU.
 CPU interconnection: Some mechanism that
provides for communication among the
control unit, ALU, and registers.
Ms. Yagni Desai

12. Parallel Port
USB
Mouse&Keyboard
Power Supply
Plug in
PCI Slot
CPU Slot
ISA Slot CPU Chip
RAM Slots
CMOS Battery Floppy Controller
IDE Controller
AGP Slot Ms. Yagni Desai

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17.  Blaise Pascal invented the first mechanical
adding machine in 1642
 In 1671, Baron GottFried Wilhelm Von Leibniz
of Germany invented the first calculator for
multiplication.
 Keyboard machines originated in the United
States around 1880 that we use today.
 Around 1880 Herman Hollerith came with the
concepts of punched cards that were used as
input medium in computers even in late
1970s
Ms. Yagni Desai

18.  Business machines and calculators made their
appearance in Europe and America towards
the end of the nineteenth century.
 Charles Babbage, is considered the father of
modern digital computers.
 In 1822 Babbage designed “Difference
Engine” that could compute statistical tables.
 In 1842, Babbage came out with his new idea
of a completely automatic Analytical Engine
for performing basic arithmetic functions for
any mathematical problem at an average
speed of 60 additions per minute.
Ms. Yagni Desai

19.  The Mark 1 Computer (1937-44):
◦ Known as Automatic Sequence Controlled
Calculator.
◦ Full Automatic calculating machine designed by
Howard A. Aiken in collaboration with IBM.
◦ Electro-mechanical device based on techniques
used in punched card machines.
◦ Reliable, but complex in design and huge.
◦ It used over 3000 electrically activated switches to
control its operations and was 50 feet long and 8
feet high.
◦ This machine was capable of performing 5 basic
arithmetic operations:
 Addition, subtraction, multiplication, division , table
reference on numbers as big as 23 decimal digits.
◦ It took 0.3 second to add two numbers and 4.5
seconds for multiplication of 2 numbers.
Ms. Yagni Desai

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22.  The Atanasoff-Berry Computer (ABC)
(1939-42) :
◦ Dr. John Atanasoff developed with his assistant
Clifford Berry to solve mathematical equations.
◦ It was called ABC after inventors & assistant name
◦ Used 45 vacuum tubes for internal logic and
capacitors for storage.
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26.  The ENIAC (1943-46):
◦ Electronic Numerical Integrator And Calculator
(ENIAC) was the first Electronic Computer.
◦ Developed by Moore School of U.S.A by Professors J.
Presper Eckert and John Mauchly.
◦ ENIAC was developed for military needs.
◦ It was huge, took 20X40 square feet room and used
18,000 vacuum tubes.
◦ It could add 2 numbers in 200 microseconds.
◦ Multiply 2 numbers in 2000 microseconds.
Ms. Yagni Desai

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28.  The EDVAC (1946-52):
◦ Abbreviated form of Electronic Discrete Variable
Automatic Computer.
◦ Drawback of ENIAC was its program wired on
boards that made difficult to change the program.
◦ Dr. John Von Newuman’s “Stored Program” concept
solved above mentioned problem.
◦ Idea behind this concept is that sequence of
instructions and data stored in memory of
computer for automatically directing flow of
operations.
◦ Multiple programs can be stored on same computer
using this “Stored Program” concept.
◦ Due to this Modern Digital Computers also called
Stored Program digital computers.
Ms. Yagni Desai

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30. ◦ Von Neumann gave idea of storing instructions and
data in binary form (0 and 1), instead of decimal
numbers or human readable form.
 The EDSAC (1947-49):
◦ Abbreviated name of Electronic Delay Storage
Automatic Calculator (EDSAC)
◦ It was developed by group of scientists headed by
Professor Maurice Wilkes at the Cambridge
University Mathematical Laboratory in May 1949
◦ Addition operation took 1500 microseconds and
Multiplication took 4000 microseconds.
Ms. Yagni Desai

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32.  The UNIVAC I (1951):
◦ Abbreviated name of Universal Automatic Computer
◦ 1st UNIVAC machines was installed in Census Bureau
in 1951 & was used for continuously 10 years.
◦ 1st business use of UNIVAC I was by General Electric
Corporation in 1954.
◦ In 1952, the International Business Machines (IBM)
corporation introduced the IBM-701 commercial
computer.
◦ Then improved models of UNIVAC I and other 700-
series machines were introduced.
◦ In 1953, IBM produced IBM-650 and sold over 1000
of these computers.
Ms. Yagni Desai

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34.  There are 5 computer generations known till
today.
 Generations with their characteristics are
stated below.
 First Generation (1942-1955)
◦ Vacuum tube is a fragile(delicate ) glass device, It
used filaments (fiber) as a source of electronics.
◦ It could control and amplify electronic signals.
◦ It was the only high-speed electronic switching
device available those days.
Ms. Yagni Desai

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36.  They were the fastest calculating devices of
their time.
 They were Bulky in size required large rooms.
 These used thousands of vacuum tubes which
emitted large amount of heat. So AC was
required in room.
 Each VT consumed half a watt of power. Each
computer used more than 1000 VT so power
consumption was high.
Ms. Yagni Desai

37.  Vacuum tubes used filaments so they had a
limited life. And Computers used vacuum
tubes so these computers had frequent h/w
failures.
 Computers frequently failed so they required
constant maintenance.
 Various individual components were
assembled by hand into electronic circuits.
Thus commercial production was difficult and
costly.
 These computers were difficult to program
and use so they had limited commercial use.
Ms. Yagni Desai

38. ◦ VT computers could perform computations in
milliseconds and were referred to as first-
generation computers.
◦ Memory of these computers used electromagnetic
relays
◦ All data and instructions were fed into the system
from punched cards.
◦ The instructions were written in machine and
assembly languages because high-level
programming languages were introduced much
later.
Ms. Yagni Desai

39.  John Bardeen, William Shockley and Walter
Brattain invented transistors in 1947
 Transistor was better than Vacuum tubes
◦ Transistors were rough and easier to handle
because they were made of germanium
semiconductor material rather than glass.
◦ They were more reliable as compared to tubes as
they don’t have filament which could burnt
◦ They could switch much faster than tubes. Hence,
switching circuits made of transistors could operate
much faster than tubes
◦ Consumed One-Tenth the power consumed by a
tube
◦ Smaller than a tube in size
◦ Less Expensive to produce
◦ Dissipated much less heat as compared to vacuum
tubes.
Ms. Yagni Desai

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42.  On software front, high-level programming
languages (like Fortran, Cobol, Algol and
Snobol) and Batch Operating System emerged
during Second Generation.
 High level language is easier to use and thus
makes programming easier
 Batch OS enabled multiple jobs batched
together and submitted at time
 Batch OS causes automatic transition from
One job to another as former jobs completes.
Ms. Yagni Desai

43. CHARATERISTICS
◦ 10 times faster than 1st Generation computers.
◦ Smaller than 1st Gen. Computers
◦ Consumed less power and dissipate less heat. But
A.C still required
◦ More reliable and less prone to H/W failures.
◦ Faster & larger primary & secondary storage
◦ Easier to program and use, hence had wider
commercial use
◦ Thousand of transistors assembled by hand in
electronic circuits making commercial production of
these computers difficult and costly.
Ms. Yagni Desai

44.  Jack St. Clair Kilby and Robert Noyce invented
first Integrated Circuits (Called ICs).
 ICs consist of several electronic components
like transistors, resistors and capacitors
grown on a single chip of silicon eliminating
wired interconnection between components.
 Larger number of circuits were integrated in
small surface (less than 5 mm square).
 SSI - Small scale Integration (10 to 20
Components Integrated)
 MSI - Medium Scale Integration (100
Components Integrated)
Ms. Yagni Desai

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47. ◦ Larger Magnetic core based random access
memory and Larger capacity magnetic
disks and tapes constructed.
◦ 3G computers had less than 5 Megabytes
of main memory and magnetic disks stores
few tens of megabytes of data per disk
drive.
Ms. Yagni Desai

48.  Standardization of high-level programming
languages
 Time Sharing OS
 Creation of Independent Software Industry
 Fortran and Cobol were the most popular
high-level programming languages
 Development & Intro of minicomputers
 In 1960 Mainframe Introduced were very
costly and unaffordable.
 Digital Equipment Corporation introduced
first commercially available minicomputer,
the PDP-8 (Programmed Data Processor) in
1965
Ms. Yagni Desai

49.  More powerful than 2nd Generation.
Performed 1 million instructions/sec
 Smaller than 2nd Gen Computers.
 Consumed less powers and dissipate less
heat but A.C still required
 More reliable and less prone to H/W failures
and so required less maintenance cost.
 Faster and Larger Primary and Secondary
storage
Ms. Yagni Desai

50.  Used for scientific and commercial
applications.
 Did not require manual assembly of individual
components into electronic circuits resulting
in reduced human labor and cost.
Commercial production was easier.
 Standardization of high-level programming
languages, program written for 1 computer
can be easily ported to and executed on
another computer.
 Timesharing OS allowed interactive usage and
simultaneous use of systems by multiple
users
Ms. Yagni Desai

51.  Timesharing OS improves productivity of
programmers cutting down time and cost
 Timesharing OS made on-line systems feasible
 Unbundling of S/W from H/W gave users
opportunity to invest only in s/w of their need
and value.
 Minicomputers of third-generation made
computers affordable even by smaller
companies.
Ms. Yagni Desai

52.  This was era of LSI(Large Scale Integration)
when 30,000 electronic components integrated
on a single chip.
 Followed by VLSI(Very Large Scale Integration)
when 1 Million electronic components
integrated on a single chip.
 Then came Microprocessor.
 A Microprocessor contains all circuits needed
to perform arithmetic logic and control
functions, the core activities of all computers,
on a single chip.
Ms. Yagni Desai

53.  Hence now a complete computer was built
with a microprocessor, a few additional
primary storage chips, and other support
circuitry
 Semiconductor Memories replaced magnetic
core memories resulting in large Random
Access Memories (RAM) with very fast access
time.
 Hard disks became cheaper, smaller and
larger in capacity.
 Compared to Magnetic tapes Floppy disks
became popular
Ms. Yagni Desai

54.  Interconnection of multiple computers to
share data.
 LAN for connecting PC’s within organization
or campus
 WAN for connecting computers located at
larger distances.
Ms. Yagni Desai

55.  OS like MS-DOS, MS-Window, and Apple’s
propriety OS developed
 GUI developed
Ms. Yagni Desai

56.  PCs were smaller and cheaper than
mainframes or minicomputers of third
generation
 Fourth Generation mainframes required AC,
PCs didn’t required AC
 Consumed less power than 3rd Gen PCs.
 More Reliable and less prone to H/W failures
so low maintenance required
Ms. Yagni Desai

57.  Faster & have larger primary and secondary
storage
 General purpose machines
 Manual assembling not required hence less
cost. Manufacturing LSI & VLSI costly
 High level Programming languages
 GUI
 Used in Office & Home
 N/W enabled sharing of data, disks
 Individuals could afford
Ms. Yagni Desai

58.  Portable PCS (Notebook Computers)
 Desktop more powerful than in 4th Generation
 No A/C required
 Less Power Consumption
 More Reliable & Less prone to H/W, less
maintenance cost
 Large scale systems have hot-plug feature
that enables failed component to be replaced
with a new one without shutdown
Ms. Yagni Desai

59.  General purpose machine
 Manufacturing does not require manual
assembly
 Standard high-level programming languages
 User- friendly
 Powerful applications using multimedia
increased comp use
 Computer for any type of user available
 Internet bade tools and applications have
made these systems influence the life of even
common people
Ms. Yagni Desai

60.  Computer architecture is based on three key
concepts:
◦ Data and instructions are stored in a single read–
write memory.
◦ The contents of this memory are addressable by
location, without regard to the type of data
contained there.
◦ Execution occurs in a sequential fashion (unless
explicitly modified) from one instruction to the
next.
Ms. Yagni Desai

61.  A small set of basic logic components that can be
combined in various ways to store binary data
and to perform arithmetic and logical operations
on that data.
 To perform a particular computation, a
configuration of logic components designed
specifically for that computation, this kind of
program is referred to as hardwired program.
 The system accepts data and produces results.
Ms. Yagni Desai

62.  As alternative,
◦ Construct a general-purpose configuration of
arithmetic and logic functions.
◦ This set of hardware will perform various
functions on data depending on control signals
applied to the hardware.
◦ The system accepts data and control signals and
produces results.
Ms. Yagni Desai

63.  Define a unique code for each possible set of
control signals, and add to the general-
purpose hardware a segment that can accept
a code and generate control signals.
 Instead of rewiring the hardware for each new
program, provide a new sequence of codes,
each code is, in effect, an instruction, and
part of the hardware interprets each
instruction and generates control signals, this
method of programming, a sequence of
codes or instructions is called software.
Ms. Yagni Desai

64.  Two major components of the system(both
constitute as CPU):
◦ an instruction interpreter
◦ a module of general-purpose arithmetic and logic
functions
 I/O components
 Memory - consists of a set of locations, defined
by sequentially numbered addresses. Each
location contains a binary number that can be
interpreted as either an instruction or data.
 CPU use internal registers for storage:
◦ Memory address register (MAR) - specifies the address
in memory for the next read or write
◦ Memory buffer register (MBR) - contains the data to be
written into memory or receives the data read from
memory
◦ I/O address register (I/OAR) - specifies a particular
I/O device
◦ I/O buffer register (I/OBR) - used for the exchange of
data between an I/O module and the CPU.
Ms. Yagni Desai

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66.  The basic function performed by a computer
is execution of a program.
 Instruction processing consists of two steps:
◦ The processor reads (fetches) instructions from
memory (one at a time)
◦ Executes each instruction.
 The processing required for a single
instruction is called an instruction cycle.
◦ It consist of fetch cycle and execute cycle.
Ms. Yagni Desai

67.  Program counter (PC) register holds the
address of the instruction to be fetched next.
 The fetched instruction is loaded into a
register in the processor known as the
instruction register (IR).
 Accumulator (AC) is of temporary storage
(like intermediate results).
Ms. Yagni Desai

68.  The processor interprets the instruction and
performs the required action. These actions
fall into four categories:
◦ Processor-memory: Data may be transferred from
processor to memory or from memory to processor.
◦ Processor-I/O: Data may be transferred to or from
a peripheral device by transferring between the
processor and an I/O module.
◦ Data processing: The processor may perform some
arithmetic or logic operation on data.
◦ Control: An instruction may specify that the
sequence of execution be altered.
 For example, the processor may fetch an instruction
from location 149, which specifies that the next
instruction be from location 182. The processor will
remember this fact by setting the program counter to
182.Thus, on the next fetch cycle, the instruction will
be fetched from location 182 rather than 150.
Ms. Yagni Desai

69.  Both instructions and data are 16 bits long.
◦ First 4 bits for the opcode
◦ 4-15 bits for address
 Opcode - is the portion of a machine
language instruction, that specifies the
operation to be performed
Ms. Yagni Desai

70. EXAMPLE
Ms. Yagni Desai

71. State Diagram of Instruction cycle
Ms. Yagni Desai

72.  The states can be described as follows:
◦ Instruction address calculation (iac): Determine the
address of the next instruction to be executed.
(Usually, this involves adding a fixed number to the
address of the previous instruction.)
◦ Instruction fetch (if): Read instruction from its
memory location into the processor.
◦ Instruction operation decoding (iod): Analyze
instruction to determine type of operation to be
performed and operand(s) to be used.
◦ Operand address calculation (oac): If the operation
involves reference to an operand in memory or
available via I/O, then determine the address of the
operand.
Ms. Yagni Desai

73. ◦ Operand fetch (of): Fetch the operand from memory
or read it in from I/O.
◦ Data operation (do): Perform the operation
indicated in the instruction.
◦ Operand store (os): Write the result into memory or
out to I/O.
Ms. Yagni Desai

74.  A signal informing a programs that an event
has been occur.
 When a program receives an interrupt signal,
it takes a specified action.
 Interrupt signal cause a program to suspend
itself to service an interrupt.
 Interrupts are provided primarily as a way to
improve processing efficiency.
Ms. Yagni Desai

75. No Interrupts
Ms. Yagni Desai

76. Interrupt:
short I/O wait
Ms. Yagni Desai

77.  Interrupt handler –
◦ A section of a computer program or of the
operating system that takes control when an
interrupt is received and performs the operations
required to service the interrupt.
◦ When the CPU gets an interrupt, it must execute a
program to handle the interrupt. These special
programs are called interrupt handlers or interrupt
handler program.
◦ It handle all interrupts occurred.
Ms. Yagni Desai

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