3. Classification on Basis of
• Purpose
– General Purpose Computers
– Specific Purpose Computers
• Functionality
– Analog
– Digital
– Hybrid
Classification on Basis of
General Purpose Computers
Specific Purpose Computers
5. Classification based on
• General Purpose Computers
– Designed to meet the needs
– Designed to solve wide variety
• Store and execute different
• Can be used to prepare
inventories, print sales
calculation and so on.
• Example: A personal computer
or at home
Classification based on PURPOSE
Computers
needs of many different applications
variety of problems and functions
different program in its internal storage
prepare pay-bills, manage
sales report, making scientific
computer used in an office
6. Classification based on
• Special Purpose Computers
– Designed only to meet
particular task or application
– Designed to solve one particular
– It therefore doesn’t posses
less expensive and fast in
– Can be used in traffic lights
forecasting, digital watches
Classification based on PURPOSE
Computers
meet the requirements of a
application.
particular problem
posses unnecessary options and is
in processing
lights control system, weather
watches
7. Classification based on
• Analog Computer
– form of computer that uses
aspects of physical phenomena
mechanical, or hydraulic quantities
being solved.
– Represented by series of waves
– Don’t require any storage
measure and compare quantities
– Example: Speedometer, Voltmeter,
Classification based on Functionality
uses the continuously changeable
phenomena such as electrical,
quantities to model the problem
waves
storage capabilities because they
quantities in a single operation.
Voltmeter, Thermometers
8. Classification based on
• Digital Computer
– form of computer that performs
operation with quantities
binary digits (0, 1)
– Represented by Pulses . Two
– Store result, Manipulate
expression
– Example: General Purpose
Classification based on Functionality
performs calculation and logical
quantities represented as digit specially
Two series 1’s and 0’s
data and Evaluate Arithmetic
and Specific Purpse
9. Classification based on
• Hybrid Computer
– form of computer in which
both the analog and digital
– The digital component serve
operations whereas analog
– Example: STD / PCO phone
using analog computer and
rate is measured in form of
Classification based on Functionality
which desirable characteristics of
digital computers are integrated.
serve as control and perform logical
analog component serves as solver
phone, communicate with a person
and the rate as charges and pulse
of digits.
10. Classification based on
• Microcomputers (Personal
– A computer with a microprocessor
supplemented with keyboard
microcomputer
– A microcomputer is the
processing system.
– These computers can fit on
– Available for only single user
– Types
• Desktops – cannot be carried
• Portables – can be used while
Classification based on Size
(Personal Computer)
microprocessor and its CPU
keyboard and mouse is known as
the smallest general purpose
on desks or tables
user at any time
carried
while travelling
11. Classification based on
• Microcomputers (Personal
– Types of Portables
• Laptop and Notebooks
• Tablet
• Smpartphones, PDAs and Palmtop
• Wearable
Classification based on Size
(Personal Computer)
Palmtop
12. Classification based on
• Minicomputers
– Medium sized computer.
– Serve multiple users simultaneously
Classification based on Size
simultaneously
13. Classification based on
• Mainframe Computers
– Computers with
• Large size
• Large storage capacities
• Very high speed of processing
• High level of reliability
– Ability to run multiple OS
– One mainframe can replace
smaller servers
Classification based on Size
processing
replace dozen or even hundred of
14. Classification based on
• Mainframe Computers
– Mainframe computers are
government, banks and large
– Can respond to up to 100s
Classification based on Size
used in large institutions such as
large corporations.
of millions of users at a time.
15. Classification based on
• SuperComputer
– Consists of ten of thousands
perform billions and trillions
– Useful in weather forecasting,
simulations etc.
– Most powerful and very expensive
Classification based on Size
thousands of processor that are able to
trillions of calculation per second.
forecasting, climate research, physical
expensive.
17. CPU
• Is the electronic circuitry within
instructions of a computer program
arithmetic, logical, control and
specified by the instructions.
• Hardwired into a CPU's circuitry
perform, called an instruction set
• Each basic operation is represented
bits, known as the machine language
• While executing instructions in
CPU decides which operation to perform
CPU
within a computer that carries out the
program by performing the basic
and input/output (I/O) operations
circuitry is a set of basic operations it can
set.
represented by a particular combination of
language opcode
a machine language program, the
perform by "decoding" the opcode.
19. CPU – Block Diagram
• Control Unit
– The control unit does not
rather, it directs other parts
– The control unit communicates
memory.
Block Diagram
not execute program instructions;
parts of the system to do so.
communicates with both the ALU and
20. CPU – Block Diagram
• Arithmetic Logic Unit (ALU)
– ALU is a digital circuit within
integer arithmetic and bitwise
– The inputs to the ALU are
from previous operations,
indicating which operation
– The operands may come
external memory, or they
the ALU itself.
– The result may be stored
status information that is
internal CPU register reserved
Block Diagram
(ALU)
within the processor that performs
bitwise logic operations
are operands, status information
operations, and a code from the CU
operation to perform
from internal CPU registers or
may be constants generated by
stored in a register or memory, and
is typically stored in a special,
reserved for this purpose.
21. CPU – Operations
• The fundamental operation
execute a sequence of
called a program.
• Nearly all CPUs follow the
steps in their operation, which
as the instruction cycle.
Operations
operation of most CPUs, is to
stored instructions that is
the fetch, decode and execute
which are collectively known
23. What are registers?
• Register is a quickly accessible
CPU.
• All computers load data
registers where it is used
and is manipulated
instructions.
• Manipulated data is then
memory, either by the
subsequent one
What are registers?
accessible location available to a
from a larger memory into
used for arithmetic operations
or tested by machine
then often stored back to main
same instruction or by a
24. Types of Registers
• Data registers can hold numeric values such as integer
• Address registers hold addresses and are used by instructions that
indirectly access primary memory.
• The stack pointer is used to manage the run
• General-purpose registers (GPRs) can store both data and addresses,
• Floating-point registers (FPRs) store floating point numbers in many
architectures.
• Constant registers hold read-only values such as zero, one, or pi.
• Instruction register (IR), holding the instruction currently being executed.
Types of Registers
can hold numeric values such as integer
hold addresses and are used by instructions that
is used to manage the run-time stack.
(GPRs) can store both data and addresses,
(FPRs) store floating point numbers in many
only values such as zero, one, or pi.
holding the instruction currently being executed.
25. Types of Registers
• Memory Buffer Register (MBR)
– register in CPU that stores
and from the immediate access
• Memory Data Register (MDR)
– a two-way register that holds
• data fetched from memory and ready for the CPU to process or
• data waiting to be stored in memory.
• Memory Address Register (MAR)
– the memory address from which data will be fetched to
the CPU
– the address to which data will be sent and store
Types of Registers
egister (MBR)
stores the data being transferred to
access store.
way register that holds
data fetched from memory and ready for the CPU to process or
data waiting to be stored in memory.
Memory Address Register (MAR) either stores
the memory address from which data will be fetched to
the address to which data will be sent and store
27. What are Buses?
• A bus is a communication
between components inside
computers.
What are Buses?
communication system that transfers data
inside a computer, or between
28. Types of Buses
• Address Bus
– is a computer bus that
address.
– When a processor needs
location, it specifies that memory
bus.
– The width of the address
memory a system can address
• For example, a system with
(4,294,967,296) memory locations
Types of Buses
is used to specify a physical
to read or write to a memory
memory location on the address
bus determines the amount of
address.
with a 32-bit address bus can address 232
locations.
29. Types of Buses
• Control Bus
– is a computer bus that carries
and returns status signals from
– Types of Lines
• Read : A single line that when
device is being read by the CPU
• Write: A single line that when
device is being written by the
• Byte enable : A group of lines
16, 32, 64 bytes).
Types of Buses
carries commands from the CPU
from the devices.
when active (logic zero) indicates the
CPU.
when active (logic zero) indicates the
the CPU.
lines that indicate the size of the data (8,
30. Types of Buses
• Control Bus
– Additional lines are microprocessor
• Transfer ACK ("acknowledgement")
data was acknowledged (read)
• Bus request. Indicates a device
bus.
• Bus grant. Indicates the CPU
• Interrupt request. A device with
to the CPU.
• Clock signals. The signal on
between the CPU and a device
• Reset. If this line is active, the
Types of Buses
microprocessor-dependent, such as:
("acknowledgement"). Delivers information that the
(read) by the device.
device is requesting the use of the (data)
CPU has granted access to the bus.
with lower priority is requesting access
on this line is used to synchronize data
device.
the CPU will perform a hard reboot.
31. Types of Buses
• Data Bus
– Is a computer bus that allows
component to another on a
– This can include
• transferring data to and from
• from the central processing
– Each one is designed to handle
time. The amount of data
bandwidth.
Types of Buses
allows transferring of data from one
a motherboard
from the memory, or
unit (CPU) to other components.
handle so many bits of data at a
a data bus can handle is called
32. Types of Buses
• Data Bus
– Types
• Parallel data buses
– Carry data on many wires
– Each wire carries one bit
– Example: the PC card and
Interface.
• Serial data bus
– Has one wire and carries
– Example : USB, also
FireWire; Serial ATA; and
Types of Buses
wires simultaneously.
bit of data.
and the SCSI, or Small Computer System
carries all the bits, one after the other.
known as the Universal Serial Bus;
and Serial Attached SCSI.
34. What is Instruction Cycle
• It is the process by which a
– computer retrieves a program instruction from its memory,
– determines what actions the instruction requires, and
– carries out those actions.
• This cycle is repeated continuously
bootup to when the computer
• The instruction cycle is
instruction is completely processed
is started.
What is Instruction Cycle
It is the process by which a
computer retrieves a program instruction from its memory,
determines what actions the instruction requires, and
continuously by the CPU, from
computer is shut down.
executed sequentially: each
processed before the next one
35. Instruction Cycle
• Program counter (PC)
– Counter that holds the address
executed next.
• Memory address register (MAR)
– holds the address of a memory block to be read from or
written to.
• Memory data register (MDR)
– a two-way register that holds
• data fetched from memory and ready for the CPU to process or
• data waiting to be stored in memory.
Instruction Cycle – Registers Used
address of the instruction to be
Memory address register (MAR)
holds the address of a memory block to be read from or
Memory data register (MDR)
way register that holds
data fetched from memory and ready for the CPU to process or
data waiting to be stored in memory.
36. Instruction Cycle
• Instruction register (IR)
– a temporary holding ground
just been fetched from memory
• Control unit (CU)
– decodes the program instruction in the IR,
– Selecting particular arithmetic operation, and coordinates
activation of those resources.
• Arithmetic logic unit (ALU)
– performs mathematical and logical operations.
Instruction Cycle – Registers Used
ground for the instruction that has
memory.
decodes the program instruction in the IR,
Selecting particular arithmetic operation, and coordinates
activation of those resources.
Arithmetic logic unit (ALU)
performs mathematical and logical operations.
37. Instruction Cycle
• Fetching the instruction:
– instruction is fetched from the memory address that is
currently stored in the program counter (PC), and
– stored in the instruction register (IR).
– At the end of the fetch operation, the PC points to the next
instruction that will be read at the next cycle.
• Decode the instruction:
– encoded instruction present in the IR (instruction register)
is interpreted by the decoder of CU
Instruction Cycle - Steps
instruction is fetched from the memory address that is
currently stored in the program counter (PC), and
stored in the instruction register (IR).
At the end of the fetch operation, the PC points to the next
instruction that will be read at the next cycle.
encoded instruction present in the IR (instruction register)
is interpreted by the decoder of CU
38. Instruction Cycle
• Execute the instruction:
– The control unit passes
sequence of control signals
of the CPU to perform
instruction
• such as reading values from
• passing them to the ALU
functions on them, and
• writing the result back to a register
• The result generated by the
memory, or sent to an output
Instruction Cycle - Steps
the decoded information as a
signals to the relevant function units
the actions required by the
registers,
ALU to perform mathematical or logic
register.
the operation is stored in the main
output device.
