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OUTPUT DEVICES
These are equipment through which the output of a computer can be viewed, heard or printed. The two most common output devices are Printers and CRT monitor.
Printer
This is the most common output device which produces a permanent record in print. There are various types of printers available and are differentiated by the quality and method of production. Examples are dot matrix printers, laser printers and ink jet printers.
CRT monitor
The most common form of display monitor is the CRT. CRT means Cathode Ray Tube. This is the type of monitor used with microcomputers. Virtually all computers used in information handling initially output their information to a display unit. The image below shows a CRT monitor. They can output either text or pictures or both in monochrome (mainly two colours, e.g. black and white) or colour.
The CPU
The main functional parts of the Central Processing Unit (CPU) are the control Unit, the Main memory and Arithmetic and logic Unit (ALU). When you start a typical personal computer by placing a disk in the drive and turning on the power, the CPU causes a program to be transferred from the disk into the high-speed internal memory, where the program takes control of the CPU.
The CPU shifts data back and forth between internal memory and disk (external memory) in order to process data. Data cannot be processed directly while stored on the disk; data must be brought into internal memory to be totalled, compared, displayed, printed, and so forth. Eventually the program gives up control of the computer and ceases to operate. When this happens, you must tell the computer what to do next.
No matter what directions you give the computer, the same pattern is followed. A program is transferred into high-speed memory, where it takes over control, process the data and finally terminates. This three-part process is called program execution or a program run. Program are run on the CPU under control of a control unit, main memory, and an arithmetic/logic unit.
The Arithmetic/Logic Unit (ALU) does all the computing. It can add two numbers, subtract, multiply, and divide. It can compare two numbers to determine which is larger, move data from one place to another and keep track of time. The ALU works exclusively on encoded binary numbers. It takes it's orders from binary encoded instructions stored like any other information in main memory.
The control unit is the supervisor of the CPU; it fetches numbers from the memory and interprets them as instructions. The control Unit treats each instruction and then directs the flow of information through the ALU, input/output devices and the main memory.
The main memory is always connected to the processor. In a computer it is usually in the same box as the processor. When you type a set of instructions on the keyboard of your computer, they are put into the main memory. When you tell your computer to obey some instructions, they are taken one by one from the main memory and put into the processor. After each instruction has been put into the processor it is obeyed.
The main memory is used to hold the instructions and Information which are being used by the computer.
The main memory has two parts, the Read only Memory (ROM) for short, and the Random Access Memory (RAM) for short. When you type the computer instructions — usually called programs — into your computer, they are put into the main memory. The part of the memory which they are put into is the RAM. RAM stores our data and program.
When you switch off your computer, all the information and programs held in the RAM disappear. If you want to use the program again you will have to type it in whenever you switch on your computer. To avoid this repetition, you have to save it in some form of secondary storage. When you turn your computer on, your computer must have some preset instructions to tell it what to do. These permanent, non-volatile instructions are programmed onto ROM chips. Other names for ROM chips are firmware, or prewired. ROM chips have many functions: for example, they tell the computer what to do when the power is turned on, they check to see that the cable to the printer is connected, and they will tell the control unit what each key on the keyboard means. Unlike RAM, users cannot normally store their own instructions on the ROM.
ROM is the preset instructions that tell your computer what to do.
CONCLUSION
The output devices and the processing devices are very important in a computer system. Memory is also very important because it's a temporary storage device that holds data and programs during execution as proposed by Von Neumann! Thanks for visiting my blog. I will be dropping Computer System Series 3 very soon, so anticipate for it!! Take care and God bless