Keyboard Heritage

So where does that leave us today? The 104-key ‘Windows’ keyboard sporting a QWERTY layout with some inherited keys held over from the dawn of personal computing. Some of the keys are re-mapped for modern systems, while others don’t do much at all – but we keep making keyboards with them on because, well, we just always have. Let’s see what the more esoteric keys are about:

Sys Rq: On its own in the 83 key layout, now also hosting Print Screen since the 102-key layout, the System Request key was originally used for the IBM 3270 mainframe and later IBM 5150 personal computer, mapped to a special BIOS routine. It was designed to invoke low-level operating system functions bypassing higher level programs – which is precisely how it’s today used by Linux kernel debuggers when the ‘Magic SysRq key’ function is enabled, allowing developers to perform low-level commands regardless of the operating system’s state. Aside from this however it is no longer used, and could be removed.

Print Screen: You know what this does, mapped to taking a screenshot of your desktop in most operating systems: in Windows there’s no feedback the capture has worked, but if you open Paint or another editor and Paste, the image will be added. In most Linux distributions it will take a screenshot and prompt you where to save it. Once upon a time however Print Screen sent a snapshot of the text console to a printer – which is why it’s called Print Screen and not ‘Screen Shot’ like its use today. Could probably do with being renamed.

Scoll Lock: The Scroll Lock key was, like Print Screen, designed for terminals where it would act as a modifier for the cursor keys – when off the cursor keys would move the cursor on screen, when on the keys would instead scroll the contents of the screen. Today the key isn’t necessary and could be removed, but like the Sys Rq key it’s a tradition that persists.

Caps Lock: The Caps Lock key is a key we do still use today. Naturally it toggles the use of alternate CAPS for letters, performing the same function as Shift but without the need to hold it down. Unlike Shift however Caps Lock is a modifier only for letters, whereas Shift modifies other keys on the keyboard as well. Caps Lock originated with mechanical typewriters where it would lock the lever for the Shift key in place once Shift was pushed (so both keys pushed), to allow typing in all caps without holding the key down.

Num Lock: Like Caps Lock and Scroll Lock, the Num Lock key is a toggle and also began on the original 83-key keyboard. Remembering cursor keys didn’t arrive until the 102-key layout, Num Lock was used on the 83-key layout to toggle the number pad to act as cursor keys for navigation and vice versa. A function it still performs today, some 30 years later, although it’s no longer necessary.

Pause/Break: Another key that could disappear and you wouldn’t miss it, the original function of the key was as Break and has a history as far back as the telegraph. In personal computers it was used on the old BBC and Spectrum computers to interrupt running programs (and would do the same in DOS, when combined with the Ctrl key). It later inherited the Pause function in the 102-key layout, which can be used at BIOS POST and in DOS to pause text display on screen. While Break is rarely used now, today Pause is sometimes respected by applications (including games) to pause the current running operation.

Alt: The Alternate key harkens back to the 83-key layout and was originally used to set the high bit (first binary digit) of key sequence for use as a key modifier before the bit was usurped for internationalisation use in sequences. Still, it retains its function as a modifier today, and unlike the original 83-key layout with just one Alt key, modern keyboards have two, accessible on either side of the keyboard. On European keyboards, the right Alt key is titled Alt Gr (Alternate Graphic) and is used for characters specific to a locale, such as generating accented letters. Finally, in addition to being a modifier, the Alt key can be used to directly enter ASCII codes for characters – for example entering Alt-35 will generate a ‘#’ under Windows, though values depend on the codepage being used.

Ctrl: Like Alt, the Control key is a modifier for other keys also brought forward from the 83-key layout. Originally it was used to produce non-printable control key sequences that would be picked up by a program to perform tasks like ejecting a page from a printer, clearing the screen, and beeping (hence the ‘Control’ terminology). Though unprintable, Control codes could none the less be generated with the right ANSI sequence and embedded in text – something IRC users will be familiar with. Naturally, you will be familiar with control sequences like Ctrl-C, Ctrl-X and Ctrl-V. Finally, like Alt, the original 83-key design had a single Ctrl key on the left side, whereas these days keyboards have a right Ctrl as well.

Esc: The Escape key generates the ASCII escape sequence that was originally used to signal a subsequent control sequence to a device. Or, said another way, the values following an escape sequence would be interpreted as a command for a device, rather than as data. While it was originally used with terminals and modems, that purpose is moot these days. Instead the key is mapped to function depending on the operating system and application, but usually to exit or ‘escape’ the current mode. Escape sequences are still used however, such as in Linux terminals.

Function: The function keys are the only keys on the keyboard without a pre-defined operation, designed instead to be used by whatever application needs them. Originally they were located as ten function keys in a two by five row of the left side on the 83-key layout. Ostensibly this caused problems with programs that listed function actions horizontally on screen (for example at the bottom of a word processor), and so they were moved to the top row. The actions they are mapped to, despite the application, have since earned their place in history – F1 is commonly used to call up help in multiple operating systems, and we all know the value of F6.

Enter: You may think you know this one but there’s a little more under the hood – interchangeable with Return, short for carriage return, this hints at the etymology of the key. Originally it was used on typewriters to return the carriage – the cylinder around which the paper was wrapped – to the left side and roll the carriage around ready for a new line. This function was shown by the 8 symbol, representing the physical action of the carriage return, and which you’ll still find on Enter keys today – even though we’re long past using carriages.

Interestingly it’s been suggested that, despite the fact that some keys no longer serve a purpose, keyboards are still produced with the full layout because it’s safer to do so than risk breaking software – however unlikely in modern systems – which might still use them.

That, or like pink hats and jumping up and down on Saturdays, they’ve simply become part of a tradition.