Jack (typewriter)
On mechanical typewriters, the jack is a key which , when pressed , changes the character assignment on the keyboard from lowercase to uppercase . The change applies until you release unless the Caps Lock key is engaged.
The keys of a mechanical typewriter were each directly connected to a lever (" type ") on which two characters were attached. Depending on whether the carriage - the movable device in which the paper was clamped - was in the lowered or raised state, the lower or upper character then hit the ribbon in front of the paper . The lower drawing level mainly contained the small letters and numbers , while the upper level contained the capital letters and some special characters.
On the computer keyboard , which is still modeled on the typewriter, the shift key takes on the function of the jack. To view all 94 visible signs of ASCII - character set to accommodate, has a US keyboard 47 keys and Shift. There are also the space bar and some keys to control the software .