Page 15 - Viva ICSE Computer Studies 7 : E-book

and a device driver. The input device attached to receive audio data is usually a microphone,
whereas the devices used for audio output are generally speakers and headphones.
The sound card converts incoming digital audio data into analog audio so that the speakers can
play it. In the reverse case, the sound card can convert analog audio data from the microphone
into digital data that can be stored on the computer.

Video Card

A video card is also known as a graphics card. It is an expansion
card connected to a motherboard, that is used to generate the
video output on a screen such as monitor and television. It
enhances the quality of the displayed images, and contains its
own processing and memory unit.

CPU

The Central Processing Unit (CPU) is the primary element of a
computer. It carries out each instruction of a program in a sequence
to perform the basic operations of the system. In other words, it
performs arithmetic and logical calculations of the data. The CPU is
capable of storing enormous amount of data and processing them at
a high speed and producing useful results.

The three components of a CPU are listed below.

1. Arithmetic Logic Unit (ALU): It performs arithmetic and logical operations.
2. Control Unit (CU): It extracts instructions from the memory, decodes and executes
them.
3. Memory Unit (MU): A computer has a large storage capacity. The storage capacity
of a computer is called its memory. Memory enables a computer to store data and
instructions.

RAM

Random Access Memory (RAM) is used to store data and instructions
during the execution of programs. RAM is temporary and is erased when
a computer is switched off . Hence, RAM is a volatile memory. It is a read/
write type of memory, and thus can only be read and written by the
user/programmer. As it is possible to randomly use any location of this
memory, therefore, this memory is known as random access memory.

Types of RAM

Two types of RAM are used in PCs: dynamic RAM and static RAM.
• Dynamic RAM (DRAM): The information stored in dynamic RAM has to be refreshed after
every few milliseconds, otherwise it is erased. DRAM is mostly used for system memory
because it is cheaper and has a higher storage capacity than static RAM.

3