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Ghosting is when some keyboard shortcuts don't work when several blocks of keys are struck simultaneously. This is purely a logical problem in keyboards with a line/column matrix switching system, manifesting itself during game play when some buttons seem not to work, only to work very slowly, or work without being struck (as if by a ghost).
An example: imagine an oblique leftward movement from A to W. At the same time you wish to input another function with Q, which either doesn't work or is acknowledged by an additional S. The buttons either seem to be unresponsive, or the above-mentioned mass of letters generated by unstruck keys appears.
Just because a keyboard is marketed with anti-ghosting capabilities does not mean all of its keys can really work simultaneously without problems. Often, only a certain number of keys are calibrated to function perfectly (for example, the WASD block and/or the direction keys). This is simpler, cheaper, and, from the perspective of a disinterested observer, covers the important bases anyway. You only run into problems once you move away from those specifically-protected keys.
Lost input is usually attributable to one of three possible causes: hardware incapable of evaluating the keyboard input (ghosting), software that doesn't support multiple simultaneous keystrokes (software issue), or a communication protocol that limits the number of keystrokes than can be transmitted simultaneously (USB versus PS/2).
Because we analyzed interfaces on the previous page, we will now explore some of the problems encountered with keyboards. What causes them?
The contacts of a keyboard are not usually evaluated individually, but rather in their switching configuration, a kind of matrix of columns and rows (see illustration). This avoids having an individual lead for each button and recognizes keystrokes based on the pattern from the interconnected columns and rows. Let's look at some simple examples of how this method works:
1. One individual keystroke
Pressing a single button can be seen as the result of a particular combination of column and row, in which the conductor of column X is circuited with the lead of row Y:
Based on the different columns and rows, the two combinations remain easily distinguished and the logic is clear: each key has only one input recognition circuit, so no problems arise, so long as the keys in question fall into mutually discrete columns and rows.3. Simultaneous keystrokes of two keys in the same column or row