Inside a Computer
A general purpose computer has four main
components: the Arithmetic Logic Unit (ALU), the
Control Unit, the Memory, and the Input and Output
devices (collectively termed I/O). These parts are
interconnected by busses, often made of groups of
Arithmetic Logic Unit (ALU)
The ALU is capable of performing two classes of operations:
arithmetic and logic
The control unit (often called a control system or
central controller) manages the computer’s
various components; it reads and interprets
(decodes) the program instructions, transforming
them into a series of control signals which
activate other parts of the computer
A computer’s memory can be viewed as a list of cells into which
numbers can be placed or read. Computer main memory comes
in two principal varieties: random-access memory or RAM and
read-only memory or ROM. RAM can be read and written to
anytime the CPU commands it, but ROM is pre-loaded with data
and software that never changes, therefore the CPU can only
read from it.
I/O is the means by which a computer exchanges
information with the outside world. Devices that
provide input or output to the computer are called
peripherals. On a typical personal computer,
peripherals include input devices like the keyboard and
mouse, and output devices such as the display and
printer. Hard disk drives, floppy disk drives and optical
disc drives serve as both input and output devices.
Input Device is any peripheral (piece of computer hardware
equipment) used to provide data and control signals to an
information processing system such as a computer or other
information appliance. Examples of input devices include
keyboards, mice, scanners, digital cameras and joysticks.
An output device is any piece of computer hardware
equipment used to communicate the results of data
processing carried out by an information processing system
(such as a computer) which converts the electronically
generated information into human-readable form.
Input Devices :
A mouse is a pointing device that functions by
detecting two-dimensional motion relative to its
supporting surface. Physically, a mouse consists of an
object held under one of the user’s hands, with one
or more buttons.
The keyboard is still the commonest way of entering
information into a computer
an alternative to the traditional mouse and often
used by graphic designers
A scanner allows you to scan printed material
and convert it into a file format that may be
used within the PC
A device that lays on the desktop and responds to
Used to allow users to point to areas on a screen
Many games require a joystick for playing of the game
The computer screen is used for outputting information in an
There are many different types of printers. In large
organizations laser printers are most commonly used due to
the fact that they can print very fast and give a very high
A plotter is an output device similar to a printer, but
normally allows you to print larger images.
Enhances the value of educational and presentation
Gives you the ability to not only to display text on a
monitor but also to read the text to you
Storage Devices — “How it saves data and
Hard disk drives are an internal, higher capacity drive
which also stores the operating system which runs
when you power on the computer.
Flash disk drives allow you to save work on small disks
and take the data with you.
The speed of a hard disk is often quoted as “average
access time” speed, measured in milliseconds. The
smaller this number the faster the disk.
Enormous! Often 1000/5000 Gigabytes. A Gigabyte is
equivalent to 1024 Megabytes.
Hard disks costs are falling rapidly and normally represent
the cheapest way of storing data.
Main Parts of Computer
Memory — “How the processor stores and uses immediate
RAM – Random Access Memory
The main ‘working’ memory used by the computer. When
the operating system loads from disk when you first switch
on the computer, it is copied into RAM.
As a rough rule, a Microsoft Windows based computer will
operate faster if you install more RAM. Data and programs
stored in RAM are volatile (i.e. the information is lost when
you switch off the computer).
How Computer Memory Is Measured
All computers work on a binary numbering system, i.e. they
process data in one’s or zero’s. This 1 or 0 level of storage is
called a bit.
A byte consists of eight bits.
A kilobyte (KB) consists of 1024 bytes.
A megabyte (MB) consists of 1024 kilobytes.
A gigabyte (GB) consists of 1024 megabytes.
• Microprocessors — “The brain of the computer“
– PCs primarily use microprocessors (sometimes called the chip).
The older Intel versions include the 386, 486 and now the
• The CPU (Central Processing Unit) is normally an Intel
Pentium (or equivalent) and it is one of the most important
components within your computer.
• It determines how fast your computer will run and is
measured by its MHz speed.
• Thus a 3200 MHz Pentium is much faster than say a 4200
MHz Pentium CPU.
• It is the CPU that performs all the calculations within the
1. One of the most important components within your computer…
a. CPU d. RPU
b. ALU e. TPU
2. There the component of inside a computer, except :
a. Harddisk d. VGA Card
b. RAM e. Processor
3. The brain of the computer :
a. Microprocessors d. Microdisk
b. Microchip e. MicroSD
4. Measurement capacity of hard drive :
a. KiloBytes d. Gygabytes
b. KiloGrams e. All Answers are True
5. Examples input device :
a. Mouse and Hard Drive d. Mouse and Printer
b. Keyboard and Memory e. Printer and Keyboard
c. Scanner and MouseExercises
1. What is the meaning of “CPU” ?
2. What are the component of inside a computer ?
3. What is the meaning of “ALU” ?
4. Can you explain about ROM, RAM ? With your own
5. What are some including the hardware computer ?
6. Mentioned examples of “Input Device” and “Output
7. Mentioned examples of Storage Device”