Computer Hardware is the physical equipment of the computer system.  Terminals, keyboard, disk drives, tape drives, printers, and the computer's brain - the central processing unit - are all hardware.  We will find out how these part work together in the computer system.

The Three Basic Operations

 The whole point of computer hardware is to make possible three basic operations:  Input, Processing and Storage, and Output.  Remember a computer cannot work without instructions from a program and information such as numbers to calculate.  The instruction and information that the computer needs are put into the computer by way of input hardware.  Once the instructions and information are in the computer, it must have processing and storage hardware to perform its work.  After the computer has finished its work, it must have output hardware.  This allows it to display its work in some way that humans can understand and use.  These hardware devices that attach to a computer are called peripherals.

All computer systems must include computer hardware to do these three operations.  But different computers use different kinds of hardware to input, process and store, and output information.  lets us look at the hardware that has been designed to serve those purposes.

Input Hardware

 Without instructions and information to tell it what to do, the computer cannot do anything.  Human programmers must write instructions for the computer.  They need to have a way to send their instructions into the computer so that it knows what to do.  This is the purpose of input hardware.  The term input simply means to put data into the computer.  You will read and hear this term often in connections with computers.  Sometimes input is referred to as data entry.

Terminals

Mouse

Modem

Voice Recognition Device

Optical Character Recognition

Processing and Storage Hardware

After the instructions and information have been entered, the computer is ready to work.  The place where it does its work is called the processor.  The processor does several jobs.  It receives the information that has been entered.  It "remembers" or stores information.  It also processes the data in some way.  The processor is made up of two parts:  the central processing unit (CPU) and main storage.

 The CPU in a microcomputer is called a microprocessor (micro means tiny).  The CPU also has two different sections.  One section is the control unit.  The control unit acts like a supervisor in an office.  It controls the other parts of the computer system and regulates the work they do.  The other section of the CPU is the arithmetic logic unit, or ALU.  The ALU does all of the calculating for the computer.  It can perform arithmetic very quickly.

 The main storage area stores instructions and information that have been entered into the computer.  It's like the way you remember things that you have learned.  In fact, computer storage is often called memory.  The computer has to remember or store instructions and data before it processes them and after it processes them.  Memory keeps the information inside the computer as it is needed.

 RAM and ROM

 You may be curious about how the memory of a computer works.  Basically, it can do two jobs:  read and write.  When the memory reads, it gets the information stored in a word.  When the computer writes, it creates a word in which to store information.  this is very much like the process you go through when you read a book to get information about a subject or write a letter to give information to someone else.

 Another kind of chip is the RAM chip.  RAM stands random-access memory.  This chip is the opposite of the ROM chip.  The manufacturer does not write programs onto the chip.  The person who buys the chip puts programs onto it.  Also, the instructions and information stored on a RAM chip can be erased and rewritten whenever the user needs to store different information.

 As computer technology has developed, computer scientists have designed smaller computers with larger memories.  This is why each new model of computer works faster and can solve larger problems that the models before it.  In fact, the smallest microcomputer on the market today works at lightning speed compared to the first, huge computers of the 1940s.

The hard disk has another important advantage over other types of memory.  With most types of main memory, the information and data stored in memory are lost when the computer is turned off.  But this is not the case with a hard disk.  With a hard disk, data and programs are stored until the user changes or erases them.  Many computer systems operate with a combination of hard and floppy disks.

 Output Hardware

 After the computer has finished processing data, it needs to have some way of sending its work back to the operator.  Otherwise, we would have no way of knowing what the computer had done and computers would be useless to us.  Sending the data from the computer back to the operator is referred to as outputting data.

A number of devices can be used to output data.  The kind of device that the operator chooses depends on what kind of output she or he needs.  If the operator needs only to see the data, then a terminal with a CRT/screen can be used.  If the operator what to have a permanent copy, usually printed on paper, then a printer can be used. 

 CRT or Screens.  Terminals displays information on a TV like device called a CRT, screen, or monitor.  The computer usually processes the information much faster than a human can follow on a terminal.  But the terminal is a very convenient way for a person to immediately see the output.

 Printers.  Probably one of the most common types of devices used to output information is the printer.  Printed books help us to remember a great deal of information on all different subjects.  If we did not have books, we would probably forget much of this information.  This is the same case with computer output.  Unless we print a permanent record of the computer output, it is easy to lose or forget it.

 Basically, there are two ways to print.  One method is impact printing.  Think of the way a typewriter prints characters on paper.  When you strike a typewriter key, the keys moves up and hits the ribbon against the paper.  This causes the ink from the ribbon to rub off on the paper in the shape of the character you typed.  This impact printing.  The other method of printing is non-impact printing.  In non-impact printing, no key strikes the ribbon against the paper to print a character.  Instead, the letters are sprayed or chemically burned onto the paper.  Intense beams of light such as lasers are now being used by some printers to burn letters on paper.