OUTPUT DEVICES PRODUCE OUTGOING INFORMATION

Each output device in a computer system accepts information from main memory under the control of the CPU, and converts it to an appropriate output form.

A printer, for example, is an output device that prints reports or graphics based on information that the CPU has processed and produced. Similarly, a video monitor is an output device that displays both text and graphics on a screen.

STORING PROGRAMS AND DATA FOR FUTURE PROCESSING

Once you turn off a computer, the data and instructions operated on by the CPU are lost. For this reason, separate storage devices are needed to keep the data and instructions in electronic form for then to be conveniently used again and again. Disks are common storage media for PCs and for larger computer systems.

A computer has two types of storage, namely main memory or PRIMARY STORAGE and external storage or called SECONDARY STORAGE. Main Memory contains computer program and the data currently being processed. It is volatile (i.e. it loses its contents when power supply is switched off). Secondary Storage stores data and programs that are not currently required by the CPU. It is transferred to the Main Memory when required. It is non-volatile (i.e. it retains data even though power supply is switched off)

SOFTWARE MAKES IT WORK

Before computer hardware can actually read data, process it, and produce information, it needs a set of instructions – a program – that actually controls the CPU operations. Programs, like data, are read into main memory under the control of the CPU.

We say that computers are stored-program-devices because they require a set of instructions to be stored in the computers main memory before data can be processed.

Computer professionals called programmers write programs for each user need or application area. The total set of programs that enables the computer system to process data is referred to as software.

TYPES OF SOFTWARE

Computers require two types of software; System Software to monitor and supervise the overall operations of the computer system and Application Software to manipulate input data and provide users with meaningful output information.