Processor and Primary Memory of Computer

The CPU and Primary Storage

•          The CPU is the part of the computer system where the manipulation of symbols, numbers, and letters occurs, and it controls the other parts of the computer system.

•          Three kinds of busses linked between the CPU, primary storage and the other devices in the computer system:

–         Data bus

•          Pass information in bi-directional. 

–         Address bus

•          Transmits signals for locating a given address in primary storage, indicating where data should be placed.

–         Control bus

•          Transmits signal specifying whether to read or write data to or from primary storage address, input device or output device.

•          The characteristics of the CPU and primary storage are very important in determining a computer’s speed and capabilities

The Arithmetic-Logic Unit and Control Unit  

•          An arithmetic logic unit (ALU) and control unit is one of the core components of all central processing units.

•          The ALU performs the computer’s principal logical and arithmetic operations.

•          It adds, subtracts, multiples, and divides, determining whether a number is positive, negative, or zero.

•          ALU must be able to determine when one quantity is greater than or less than another and when two quantities are equal.

•          The control unit coordinates and controls the other parts of the computer system.

•          It reads a stored program, one instruction at a time and directs other components of the computer system to perform the program’s required tasks.

Processor

•          Which processor should you select?

•          The faster the processor, the more expensive the computer

Primary Storage

•          Primary storage is a category of computer storage, often called main memory.

•          Has three functions:

–         Stores all or part of the program that is being executed.

–         Stores the operating system programs that manage the operation of the computer.

–         Holds data that the program is using.

•          Data and program are placed in primary storage before processing, between processing steps and after processing has ended prior to being returned to secondary storage or released as output.

Memory

•          How is memory measured?

•          By number of bytes available for storage

•          Modern primary storage devices include:

–         Random access memory (RAM)

•          is used for short-term storage of data or program instructions. RAM is volatile. Its contents will be lost when the computer’s electric supply is disrupted by a power outage or when the computer turned off.

–         Read-only memory (ROM)

•          can only be read from. It cannot be written to. ROM chips come from the manufacturer with programs already burned in, or stored. ROM is used in general-purpose computers to store important or frequently used programs, such as computing routine for calculating the square roots of numbers.