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MERCEDES PASSANO
COMPONENTS OF A COMPUTER SYSTEM
A computer is a machine that processes information. What mean by “processes” is that the information
put into the computer has something done to it. We ask the computer just to store the information so that
it can be easily found when we need it.
BACKING STORE
CPU
INPUT DEVICE
(DATA)
OUTPUT DEVICE
(INFORMATION)
A SIMPLE COMPUTER SYSTEM
Input devices allow us to enter raw data into a computer. The computer processes the information and
then produces outputs that we can understand using an output device.
Today many of the jobs we take for granted such as weather forecasting, space travel, and clearing
cheques would be almost impossible without computers. Without a computer these jobs would need so
much paperwork and so many people that they would be very expensive and impractical.
HARDWARE:
Hardware is the physical aspect of computers, telecommunications, and other information technology
devices. Hardware is the parts you can touch or see. The different items, which fit together to make the
computer systems, are called hardware. For example the screen, keyboard and mouse are all
“hardware”. Includes not only the computer proper but also the cables, connectors, power supply units,
and peripheral devices.
SOFTWARE:
Software is the program that contains the instructions that tell a computer what to do. Software is a
general term for the various kinds of programs used to operate computers and related devices. Software
exists as ideas, concepts, and symbols, but it has no substance, software is untouchable.
Software is often divided into two categories:
• Systems Software : Includes the operating system and all the utilities that enable the computer to
function. For example: Windows XP, Linux, Mac OS, etc.
o GRAPHIC USER INTERFACE: A graphical user interface (GUI - sometimes pronounced GOOee) uses pictures to make it easier for the user. It is more user friendly. The example below is
from Windows 95/98. The use of drop-down menus, windows, buttons, and icons was first
successfully marketed by Apple on the Macintosh computer. These ideas are now as
standard for graphical interfaces as door knobs are for doors.
o COMMAND LINE INTERFACE: A text-based interface means typing in all the commands. If
you mis-type, you have to backspace to your error, which erases what you already typed.
It's hard to have fun this way! But you still have to spell and type well. DOS is an example.
• Applications Software : Includes programs that do real work for users. For example, word
processors, spreadsheets, and database management systems fall under the category of
applications software.
DIFFERENCE BETWEEN HARDWARE AND SOFTWARE:
Hardware without software is like a lamp without electricity; all the parts are there, but nothing's working!
Every computer, therefore, needs software.
Hardware implies permanence and invariability. Software or programming can easily be varied. You can
put an entirely new program in the hardware and make it create an entirely new experience for the user.
INFORMATION TECHNOLOGY
MERCEDES PASSANO
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Software can be thought of as the variable part of a computer and hardware the invariable part.
The distinction between software and hardware is sometimes confusing because they are so integrally
linked. Clearly, when you purchase a program, you are buying software. But to buy the software, you
need to buy the disk (hardware) on which the software is recorded.
THE MAIN COMPONENTS OF A GENERAL-PURPOSE COMPUTER: PROCESSING
CPU (central processing unit): is an older term for processor and microprocessor, the central unit in a
computer containing the logic circuitry that performs the instructions of a computer's programs. The CPU
is the brains of the computer. In terms of computing power, the CPU is the most important element of a
computer system.
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Motherboard which holds the MICROPROCESSOR, main memory (RAM and ROM), and has slots for
expansion cards.
Power Supply - a case that holds a transformer, voltage control and fan .
Storage controllers, of IDE, SCSI or other type, that control hard disk , floppy disk, CD-ROM and other
drives; the controllers sit directly on the motherboard (on-board) or on expansion cards.
Graphics controller that produces the output for the monitor .
The hard disk, floppy disk and other drives for mass storage .
Interface controllers (parallel, serial, USB, Firewire) to connect the computer to external peripheral
devices such as printers or scanners .
Main/internal memory:
Main store, or computer memory, is divided into ROM or Read Only Memory and RAM or Random Access
Memory.
ROM is memory that cannot be changed by a program or user. ROM retains its memory even after
the computer is turned off. For example, ROM stores the instructions for the computer to start up when it is
turned on again. The operating system is loaded from the hard disk and stored in RAM whilst the machine
is being used.
RAM is a fast temporary type of memory in which programs and data are stored whilst the
computer is switched on. For example, when you load a word processing program it is loaded into RAM.
The contents of the computer's screen is also held in RAM. If the computer loses power, data stored in
RAM is lost.
So bigger memory helps make the computer work faster. When the computer is switched off everything
in the internal memory is lost! The internal memory is left empty ready to start again next time the
computer is switched on.
Input devices: transfer data into a computerised information system so that it can be processed.
Remember that the computer does not process information it processes data. An input device transfers
data from the outside world into a computer.
For example, a keyboard is an input device, Input devices other than the keyboard are Mice, trackballs,
and light pens.
Output devices: display information that has been held or generated within a computer.
Common output formats are printed-paper, saved disk file, sound, video and on-screen documents. They
are all of those things that let your computer 'talk' back to you and present information. Output devices
include display screens, loudspeakers, and printers.
Secondary backing storage: Backing storage is used for long-term data storage, usually on magnetic
tape, magnetic disc or compact disc. Common examples of backing storage devices are floppy disks,
Hard disks, and optical Disk (CD and DVD ROMs).
Backing storage devices store data that is in a computer's memory until it is needed again. When a
computer is switched off the data in RAM is lost.
When the user wants to access the data from backing storage it is copied to the main/internal memory
(RAM) of the computer.
INFORMATION TECHNOLOGY