The Central Processing Unit (CPU)

The Central Processing Unit or the CPU comprises of the Primary Memory, Control Unit and the Arithmetic And Logical Unit (ALU).

1. Control Unit: is the nerve center of the Central Processing Unit. It does the following basic functions:

Directs the flow of the input from the Input Device to the Primary Memory
Directs the flow of raw data to the ALU to be processed
Interprets instructions in the program
Redirects processed data alugueldecacambassp from the ALU to the Memory
Directs the flow of meaningful information from the Memory to the Output Device
2. Arithmetic And Logic Unit: It serves the following purpose:

Mathematical Manipulations: involving simple arithmetic calculations such as addition, subtraction, etc
Logical and Comparative Analysis: consisting of comparisons such as “greater than”( > ), “less than” ( < ), “equal to” ( = ), etc. Besides, conditional operations such as “AND”, “OR”, “NOT”, etc are also done here
3. Primary Memory: is the internal storage within the computer that sores unprocessed and processed data as well as program instructions. It is called “Primary” since it is the only memory from which the computer can access information directly and process it. It is of limited capacity and can store limited information.

The Primary Memory is categorized into two parts:

Read Only Memory (ROM): this is that part of the memory which is ONLY read by the computer. This memory already has fixed instructions on it i.e. instructions related to the operating system which are permanently imprinted on physical components by the manufacturer and not changeable by the user.
Random Access Memory (RAM): that part of the memory which is accessible to the user. The data and instructions fed in by the input device are stored in the RAM. The information stored here is temporary and exists only till the time the program is in use. The moment another program is loaded, the initial program stored in the RAM gets deleted. As opposed to this, the information stored on the ROM remain intact even after the computer is switched off while that on the RAM gets wiped out.
Secondary Memory: It would serve well to take a moment to learn about another memory type – the Secondary Memory. At times it is necessary to retain the program for future use. The Primary Memory would not serve this purpose and this comes in the Secondary Memory also called the “Backing Storage”. Secondary Memory and input output devices are physical equipment external to the CPU and are known as peripherals. The information on the secondary memory can be retrieved by feeding it into the computer’s primary memory via the input device. The circuit link between the input/output devices and the CPU is referred to as the Interface.

We learned quite a lot today that forms the basic principles in understanding computers. We shall next look into some more of these concepts in the following classes.

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