Input Devices

Consider the program.

LET MILES = 45678.3 - 45149.6
LET GALLONS = 12.5
PRINT MILES / GALLONS
END

Every time you run the program it will do exactly the same thing. The next time you fill up your gas tank again, you would have to change the program to calculate with the new values. The program is not very useful.

Most useful computer programs input data from various sources when they run. Input means data that comes from outside the program. A program that does this can work with new data each time it is run.

Sources of Input Data

• the keyboard
• a hard disk
• a floppy disk
• a CD-ROM
• the mouse
• a video camera
• an audio digitizer (part of a sound board)
• the Internet
• hundreds of other sources

For us, most data will come from the user of a program typing on the keyboard. Some sources of data (like audio data) require special hardware. A piece of hardware that is a source of input to a computer program is called an input device.