2.1.1. The motherboard
The motherboard , also known as the system board, is the main component of the system unit. It contains a number of electrical circuits and a number of slots (see Figure 2-4) for the connection of all the other components. These components comprise:
 The processor
 The Input/Output Devices e.g. Mouse, Keyboards etc…
 The different expansion cards mentioned before.
Figure 2-4: A motherboard.
The connection of these components can be done in a number of different ways.
Some devices e.g. the Keyboard, Video Display Unit etc. can be connected very easily from the outside. Other components may require some technical knowledge. For example, a Sound Card has to be connected in a slot found inside the System Unit. A
Network Card requires even more technical knowledge, as its settings have to be adjusted for its proper functioning.
The main memory as well as the microprocessor has specific slots on the motherboard.
Their legs (see Figure 2-5) are connected to the appropriate circuits on the motherboard and hence to the other devices for the proper functioning of the computer.

Figure 2-5: A memory chip.
There are a number of different types of motherboards available on the market. These differ mainly in terms of processor, amount of memory and cards they can accept. Figure
2-6 shows two different motherboards where we can easily spot the different layouts of components.
(a)
Figure 2-6: Two different motherboards
(b)
2.1.2. The processor
The processor , also known as a CPU or Central Processing Unit, is the heart of the computer, whether it is a desktop machine, a server, or a laptop. All data are processed in it.
When the processor is composed of only one chip, it is called a microprocessor . There are a number of different types of processors available on the market nowadays. The microprocessor may be a Pentium from Intel Corporation, a K6 from AMD, a PowerPC, a Sparc or any of the many other brands and types of microprocessors, but they all do approximately the same thing in approximately the same way.