COMPUTER NETWORKING ARCHITECTURE: THE BASIC MODULES

 The main modules that constitutes a computer:

The memory

The processor

The exchange units

MEMORY

Memory holds all the data used by the processor.  There are two types of data:

A series of instructions

Data on which to execute these instructions

The information stored in a memory only becomes meaningful once it is used. 

**If it is handled by a program, it consists of data, and if it is read by the control unit to be executed, it consists of instructions.

For example: If we double click on the icon of a word processor, then this program, stored on a drive, is transferred to memory using a program called a LOADER, which sees it as "data" until becomes a "program" to the user.

Memory is also known as memory words, made up of m electronic elements that can exist in two stable states referred to as "0" and "1".  

Each cell is identified by a number - its address.  The information in the memory is accessed by setting n lines of the address buses.  The binary configuration of these n lines codes the address of the word, whose m bits of content can then be read by the data bus.

The unit of memory size is generally a byte, in which case it is expressed in kilobytes (kB), megabytes (MB) or gigabytes (GB), with:

1 kilobyte = 2^10 bytes = 1024 bytes

1 megabyte = 2^20 bytes = 1048576 bytes

1 gigabytes = 2^30 bytes = 1073741824 bytes

Volatile memories are usually known as RAM (Random Access Memory) and non-volatile memories as ROM (Read Only Memory).

PROCESSOR

The processor has two functional units:

The control unit

The processing unit

THE CONTROL UNIT

The control unit has 3 functions:

It fetches instructions in the memory: it sets the address of the instruction on the address bus, then after a delay long enough to ensure that the address is in fact stable on the data bus, it loads the instruction it has just obtained into a register.

It decodes the instructions

It indicates to the processing unit which arithmetic and logic processes need to be performed and generates all of the signals necessary to the execution of the instruction.  This is the execution step.

THE PROCESSING UNIT