Caps lock is a lock key found on most keyboards. Its purpose is to allow easy entry of capitalised letters; even in countries such as Japan where letter case does not exist, it is present for when the keyboard is used for text entry in European languages, primarily English. (The majority of the world's written systems do not in fact have a concept of case, but most countries keyboards feature Latin alphabet legends on the keys.)
Unlike the shift lock key, which locks shift down as with a typewriter, caps lock only affects the letter keys. With caps lock engaged, some systems, especially Microsoft Windows, support lowercase entry by holding shift to reverse caps lock; OS X does not support this behaviour. Acorn MOS on the Acorn BBC Microcomputer supports this behaviour when caps lock mode is engaged by pressing shift+caps lock.
Caps lock is a widely hated key. It usually occupies a prominent place between Tab, Shift and A, and is easily engaged by mistake when reaching for A. To avoid this mistake, many keyboards have a stepped caps lock keycap that places a gap between caps lock and the adjacent letter key. The key placement is controversial, and it is argued that the control key is much easier to use when placed where caps lock is normally situated. There are adapter kits to swap the caps lock and control keys on existing keyboards, as they typically have different keycap shapes and sizes.
There are multiple legends for the caps lock key. English keyboards normally use "Caps Lock". German keyboards are more likely to depict a downwards arrow, but a padlock symbol was also widely used; the padlock symbol is often referred to as a handbag (US: purse) due to its peculiar shape. European symbolic Apple keyboards typically show a normal shift arrow with a square below it.
Cherry G80-2510 shows a stylized handbag.
Cherry G80-2550 shows a stylized handbag. Variant with step and blue down arrow.
Cherry G80-3011 shows a stylized handbag. Variant with step in blue (Olivetti).
Cherry G80-1000 with step and the usual down arrow.
Cherry G80-0778 labeled Groß (big)
Cherry G80-9013 with indicator LED and the usual down arrow.
Cherry G80-1501 with LED and down arrow (light grey version).
Cherry V80-5000 shows a stylized handbag.
Olivetti KBD2812 (Cherry G81-3000) shows a stylized handbag.
Cherry G80-9xxx Alcatel OEM Phoneboard
Cherry G80-0801 (Nixdorf OEM)
[Nixdorf Softclick], OEM by Cherry
Symbolic caps lock from a European AppleDesign Keyboard for Macintosh
Half-finished cap from Signature Plastics