CENTRAL PROCESSING UNIT

WHAT IS A COMPUTER?

The termcomputer is used to describe a device made up of a combination of electronic and electromechanical components. Computer has no intelligence by itself andis referred to as hardware. A computer system is a combination of five elements:

• Hardware

• Software

• People

• Procedures

• Data/information

Software is the term used to describe the instructions that tell the hardware how to perform a task. Without software instructions, the hardware doesn't know what to do.People, however, are the most important component of the computer system: they create the computer software instructions and respond to the procedures that those instructions present.

The basic job of the computer is the processing of information. Computers accept information in the form of instruction called aprogram andcharacters calleddatato perform mathematical and logical operations, and then give the results. The data israw material whileinformation is organized, processed, refined and useful for decision making. Computer is used to convert data into information. Computer is also used to store information in the digital form.

HARDWARE, SOFTWARE, AND FIRMWARE

The units that are visible in any computer are the physical components of a data processing system, or hardware. Thus, the input, storage, processing and control devices are hardware. Not visible is the software— the set of computer programs, procedures, and associated documentation.

Systems softwareare the programs designed to control the operation of a computer system. They do not solve specific problems.

Applications softwareare the programs written to solve specific problems (applications), such as payroll, inventory control, and investment analysis.

Often programs, particularly systems software, are stored in an area of memory not used for applications software. These protected programs are stored in an area of memory called read only memory (ROM), which can be read from but not written on.

Firmwareis a term that is commonly used to describe certain programs that are stored in ROM. Firmware often refers to a sequence of instructions (software) that is substituted for hardware.

CENTRAL PROCESSING UNIT

In digital computers the CPU can be divided into two functional units called the control unit (CU) and the arithmetic-logical unit (ALU). These two units are made up of electronic circuits with millions of switches that can be in one of two states, either on or off.

The function of the CU within the central processor is to transmit coordinating control signals and commands. The control unit is that part of the computer that directs the sequence of step-by-step operations of the system, selects instructions and data from memory, interprets the program instructions, and controls the flow between main storage and the arithmetic-logical unit.

The ALU, on the other hand, is that part of the computer in which the actual arithmetic operations are performed.

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