On the keyboard each key is attached to a spring and a tiny electrical switch. When you press a key, the switch closes and this sends a signal to the PC. In addition to the main characters, there is a row of 12 function keys along the top of the keyboard. These do different things according to the program you are using. The only standard is that F1 will normally display Help. If you hold down a key, the character appears once then, after a short delay, the character is repeated until you lift off the key.
