When someone types on a computer, he or she uses two types of characters: print and non-print. The print characters are the letters, numbers and symbols seen and represented on the document, while the non-print characters are the characters that control placement of the symbols but do not show up the document. These are also known as control characters, and they are used quite often without users realizing it. In the American Standard Code for Information Interchange (ASCII) there are 32 control characters, and most are used every day by regular computer users.
The control character set got its name because the main function of these characters is to control the placement of other characters. With a control character, a user can place a space between letters or correct mistakes. Most uses of a control character are from a single button push, but others may need to have two buttons pressed in conjunction.
There are many common control characters, such as the space bar. When a control character such as the space bar is used, it has a visible effect on the screen. While the effect is visible, it does not create a symbol that can be read. Other common control character keys include tab, delete, enter and shift. None of these non-printing characters is seen on the screen, but each has a dramatic effect on document creation and is used consistently by all users.
Most control character keys are activated by pushing a single key, such as the space bar. Some commands need the command button to be pressed along with another key pushed to activate an effect. These control characters are more for advanced place setting and are used less often. For example, pressing the command and backslash (\) keys is used as a file separator, which most users will not need for regular document creation.
The ASCII non-printing characters were first used with teletype machines that could communicate with other teletype machines. They also were used to enter command lines into primitive computers. Control characters are now used on every device that has text entry, though some smaller devices may not have all the control characters, such as the tab key.
Another character set, known as The Unicode Consortium, is a type of coding that deals with text and symbols on documents. This set contains all the ASCII control character keys along with a few extras for advanced setting. Unlike ASCII, which is specified as American, Unicode is used in international programs.