The Central Processing Unit (CPU) is the main component of a computer hardware system. It is the brain of a computer system consisting of the control unit, the arithmetic and logic unit and the register.
THE CONTROL UNIT: This is the unit that controls the whole operations of the system. This is done under the direction of the programs.
ARITHMETIC AND LOGIC UNIT (ALU): This has two main duties. It carries out all the required arithmetic operations like addition, subtraction, multiplication and division. It also performs some logical operations like comparing two numbers to know which is smaller.
THE REGISTER: This helps to store data and information, thereby saving the CPU time that would have been used to retrieve stored information. Accumulator, Program and Instruction register are three very important registers in the CPU.
The memory of the computer system consist of two parts
(a) Primary or main memory and
(b) Secondary or auxiliary memory
PRIMARY OR MAIN MEMORY CONSIST OF THE RAM AND ROM
RANDOM ACCESS MEMORY (RAM): Data and information of the user are stored in the RAM before processing is done in the CPU. This type of memory loses its contents when power is switched off, if data is not saved. There are two types of RAM namely: dynamic and static RAMs.
READ ONLY MEMORY (ROM): This is a non-volatile memory and does not lose its content or data when power is switched off. Data or contents are permanently stored in ROM.
HARD DISK DRIVE (HDD): A Hard Disk Drive is used for storing and retrieving digital information using one or more rigid rapidly rotating disks. It is the computer main storage.
SECONDARY OR AUXILIARY MEMORY
This includes devices like;
TAPE DRIVERS: It stores data on magnetic tapes sequentially. They are otherwise known as Sequential Access Storage Devices (SASD). Tape drives can record data at a very high density.
FLOPPY DISKETTE DRIVES: This is known as flexible disk and holds data like hard disk. Data can be stored on both sides; it is a double density disk (DD) and Single Sides Disk, data can be stored only on a single side (Single Sides Disk). Its capacity ranges from 100 KB (kilobyte) i.e. (100 x 1022 bytes) to 1.44 MB (megabytes).
UNITS OF STORAGE IN MEMORY DEVICES
1) BIT – SHORT FOR BINARY DIGITS: Either 0 or 1 in the binary number system computer processing and storage. A bit is the smallest unit of information handled by a computer.
2) NIBBLE: This is the computing term for a four-bit aggregation, or half an octet (an octet being an 8-bitbyte). A full byte is represented by two hexadecimal digits, therefore it is common to display a byte or information as two nibble.
3) BYTES: It is a unit of information consisting of 8 bits. In computer processing and storage, a byte is the equivalent of a single character. Such as a letter, a numeral or a punctuation mark. Because a byte represents only a small amount of information. Amount of computer memory and storage are usually given in kilobytes (1,024 bytes) or megabyte (1,048,576 bytes).
4) KILOBYTE (KB): It is a unit of measurement indicating kilobyte (KB) one thousand and twenty four bytes (1024bytes)
5) MEGABYTE (MB): It is a unit of measurement indicating either 1 million bytes or 1,048,576 bytes 220 i.e.1024 x 1024 x 1024 x 1024 bytes.