computers devices detail

1. Course Title: Computer in Business
Department of Business Administration
computer in business

2. Computer:
The word Computer comes from „compute‟,
meaning calculating or computing. But a
computer‟s function is lot more than that. We
can define computer in a slightly different view:
“A computer is an electronic tool that can be
programmed to do any function.”
That means it can be instructed to do whatever
we want it to do.

3. Basically, the computer consists of two
parts. These are: 1. Hardware.
2. Software.
Hardware:Any machinery(most of which
uses digital circuits) that assists in the input,
processing, storage, and output activities of
an information system.
Software: Softwares are set of instructions
written for computer hardware to slove
specific problems. They are also called
programs.Programs are classified depending
on their purposes or uses.

4. Hardwares are divided into four major units. They
are as follows: 1. Input unit.
2. Processing unit.
3. Output unit.
4. Storage unit.
This presentation focuses on the major processing
devices of a computer and on their processing
systems.

5. Below is a simple model of a computer:
Communications
devices
Secondary
storage
Input devices Output devices
Control
unit
Arithmetic/
logic unit
Register storage area
Memory
Processing device

6. Processing unit executes programs and produces
results based on the input data. Data and programs
are usually stored in primary memory for
immediate access by the processors. For
permanent storage and future use, data and
programs are stored in secondary memory. Devices
responsible for sole processing are considered as
processing unit. In microcomputer, the processing
unit is known as the microprocessor.

7. Microprocessor- the basic processing device:
Depending on the architecture used computer
systems can have only one processor, often called
CPU (Central Processing Unit), or more than one
processor connected to work in a cooperative
manner.
Processors are put into single chips called
microprocessors. A microprocessor is built in such
a way that it can accomplish most of the processing
required in a computer. With the aim of processing
data, a microprocessor executes instructions. These
instructions are generally stored in the main
memory of a computer system.

8. A microprocessor has different units inside. They
commonly work in a coordinated way. This
coordination is achieved by supplying a common
clock signal among them. The frequency of this
clock signal is called the clock speed of the
microprocessor. The higher the clock speed of a
microprocessor, the faster it works.
Examples of microprocessor: Intel core i5,
Corei7, AMD Duron etc.

9. The following are the images of some of Intel’s
processors:
Backside of an
Intel pentium
processor

10. A typical microprocessor used in personal
computers has four basic units. They are:
1. Control unit
2. Arithmetic and Logic unit (ALU)
3. Registers and
4. Cache.
All these units are interconnected. Their
interconnections are called buses. These
units and theirfunctional connections are
shown in the next figure.

11. Processing device: Microprocessor
(1) Fetch
(2) Decode (3) Execute
(4) Store
I-time E-time
Figure: A simple model of a microprocessor
architecture.

12. The control unit of a microprocessor is a
collection of some complex electronic circuits,
responsible for directing and coordinating most
activities inside and outside the microprocessor.
It controls the directions of all electronic signals
including the signals between main memory and
I/O devices, and those between main memory
and ALU.

13. The job of ALU is simple-performing arithmetic
or logic operations on given data under the
supervision of the control unit. Most ALU can
perform arithmetic operations like addition,
subtraction, multiplication and division, and logic
operations like comparisons, boolean operations
etc. Comparing two numbers result in a boolean
value

14. Registers are small-sized memory within the
microprocessor. They store instructions, memory
locations and data. The instruction that a
microprocessor currently executes is stored in
Instruction Register. The location or address of
memory that contains the next instruction is also
stored in another register called Program
Counter. Data for arithmetic and logic unit are
first brought into and stored in registers before
any operation. Results of operations are stored
in registers. Common microprocessors have up
to 32 or even higher registers.

15. Cache is a little size, very fast memory within the
microprocessor that stores frequently used
instructions and data. As cache memory is about
ten times faster than the main memory (DRAM),
an overall speedup of several factors is possible.
The built in cache memory is also called L-1
(level one) cache because most computer systems
now have an external or L-2 (level two) cache in
addition to the internal or L-1 one.

16. Here is a simple model of the cache memory:
CPU
Memory
(main store)
Cache
controller
Cache
memory

17. Buses are the connections between different
units within the microprocessor and other parts
such as the memory. When a bus is shared
among many units, the bus is often called system
bus. However, when a bus is used to connect
only two parties, it is called local bus.
Depending on the meaning of the signals carried,
there are three types of busses- data bus, address
bus and control bus.

18. Machine cycle
Instruction phase
Execution phase
Instruction phase
Step 1: Fetch instruction
Step 2: Decode instruction
Execute phase
Step 3: Execute instruction
Step 4: Store results

19. Machine cycle time
Time it takes to execute an instruction
Slow machines
Measured in microseconds (one-millionth of
a second)
Fast machines
Measured in nanoseconds (one-billionth of a
second) to picoseconds (one-trillionth of a
second)
MIPS: Millions of instructions per second

20. 1. Computer & Information System
by Sarah E. Hutchinson & Stacey C. Sawyer
2. Introduction to Computers
by Mohammad Alamgir
3.www.wikipedia.org
4.www.ask.com