A typewriter by another name
The computer keyboard is a descendant of the typewriter, and that fact explains much of its appearance. Practical typewriters appeared in the 1870s, and over the following decades the basic arrangement of keys, a shift key for capital letters and a lever for starting a new line became familiar to office workers around the world. When engineers later needed a way to feed text and numbers into machines, they did not design a new device from nothing. They adapted what trained typists already knew.
Two other technologies carried the typewriter’s keys toward computing: the keypunch and the teleprinter.
Keypunches and teleprinters
For much of the twentieth century, data was prepared for business machines on punched cards. An operator sat at a keypunch, which looked like a heavy typewriter, and typed to make holes in a card for each character. The cards were then read by a machine. Early electronic computers in the 1940s and 1950s often took input this way or through paper tape, so the person at the keyboard and the computer might be in different rooms and use different machines.
Teleprinters, also called teletypes, were the other main route. Developed for sending text over telegraph and telephone lines, they combined a keyboard with a printing mechanism. A message typed at one end was printed at the other. Because they already produced electrical signals for each key, they were a ready-made way to connect a person to a computer. By the 1960s, teletype machines were commonly used with time-sharing systems, where a number of users typed at separate terminals and the computer served them in turn. The user typed a command, and the machine printed the response on paper. Many of the conventions used by operating systems today, including the line-based command prompt, took shape in that setting.
From paper to screens
In the 1970s, video terminals began to replace printing teletypes. A terminal had a keyboard and a screen, usually showing a grid of text characters, and sent what was typed to a computer over a cable. Typing a line and waiting for paper gave way to seeing text appear immediately on a display, and users could correct mistakes before sending. Keyboards at this time still carried features of their ancestors, such as a Return key whose name goes back to the carriage return of a typewriter.
When the first personal computers appeared in the late 1970s, many put the keyboard and computer together in one case, or attached a keyboard to a television screen. Some early hobbyist machines used flat membrane keypads or small keys that were unpleasant to use, while others had full-travel typewriter-style keys. The IBM PC introduced in 1981 came with a separate keyboard that many typists found comfortable, and later IBM designs from the mid-1980s became a long-lived pattern for the standard layout that other makers copied or adapted.
The extra keys
A computer keyboard has many keys a typewriter lacks. Most of them arrived to solve specific problems.
- Control (Ctrl). On teletypes, a control key was used with a letter to produce a signal that was not a printable character, such as a bell or a command to the line. The idea carried over to computers, where Ctrl combined with a letter became the basis of many shortcuts.
- Escape (Esc). Originally used on terminals to signal that the characters following it were a command rather than text. It has since become a general-purpose cancel key.
- Function keys. The row of F-keys gave programs a set of keys whose meaning could change from one application to another. Some software printed paper overlays to sit above the keys as a reminder.
- Arrow keys and the numeric keypad. Cursor keys allowed movement around a screen without retyping. The separate number pad, borrowed from adding machines, suited people entering many figures.
- Alt, Home, End, Page Up, Page Down and Delete. These grew out of text editing and navigation needs on screen-based terminals.
- Platform-specific keys. Apple’s Command key and the Windows key on PC keyboards appeared as graphical systems added shortcuts for their menus.
The codes behind many of these keys, including the control characters, come from the character encoding standards of the 1960s.
Change and continuity
Keyboards have changed in construction. Designs have used mechanical switches, rubber domes, thin scissor mechanisms for laptops, and on-screen touch keyboards for phones and tablets. Wireless connections have removed the cable. Some people use ergonomic split designs, which aim to reduce strain, although the evidence on their benefits is mixed.
Yet the arrangement of the main letter keys has barely moved since the nineteenth century, and the way we type commands is recognizably descended from teletype practice. The keyboard remained the main text input device because no rival has yet beaten it for entering long, accurate text. Both speech recognition and handwriting recognition have improved, but typing is still widely used for writing, programming and many other tasks. The reasons the letters sit where they do are a story of their own, tied to the typewriter and its myths.