Regardless of differences in physical appearance, virtually
every computer may be envisioned as being divided into six logical units or
sections. these are:
1.Input unit. this is the "receiving"dection of
the computer. it obtains information[data and computer programs ] from various
input devices and places this information at the disposal of the other units so
that the information may be processed. Most information is interred computers today through typewriter-like key-
boards,"mouse"devices and disks. In the future , most information
will be interred by speaking to computers, by electronically scanning images,
and by video recording.
2. output unit: This is the "shipping section of the
computer. It takes information processed by the computer and places it on
various output devices to make the information available for use outside the
computer. information output from computer is displayed on screens, printed on
paper, played through audio speakers, magnetically recorded on disks and tapes,
or used to control other devices.
3.Memory unit: This is the rapid access, relatively low
capacity"warehouse"section of the computer. it retains information
that has been entered through the input unit so that the information may be
made immediately available for processing when it is needed. The memory unit
also retains information that has already been processed until that
information can be placed on output
devices by the output unit. The memory unit is often called either memory,
primary memory or random access memory[Ram].
4.Arithmetic and logic unit [Alu]. This is the
"manufacturing" section of the computer. It is the responsible of
performing calculations such as additions, subtraction, multiplication and
division. It contains the decision mechanisms that allow the computer, for
example, to compare two itemed from the memory unit to determine whether or not
they are equal.
5.central processing unit [Cpu]. This is the "administrative"
section of the computer. It is the computer's coordinator and is responsible
for supervising the operation of the other sections. The cpu tells the input
unit when information should be read into the memory unit, tells the alu when information
from the memory unit should be utilized in calculations and tells the output
unit when to send information from the memory unit to certain output devices
6.secondary storage unit: This is the long- term , high-
capacity "warehousing"section of the computer . programs or data not
being used by the other units are normally placed on secondary storage
device[such as disks] until they are needed, possibly hours, days, months or
even years later. Information in secondary storage takes longer to access than
Information in primary memory. The cost per unite of secondary storage is muss
less than the cost per unite of primary memory.
