Signedness is a property of nearly all of the numeric data types used within the NetHack source code. The word "signed" refers to the fact that these variables can store negative values; unsigned variables cannot. Its use is reponsible for the many seemingly non-round numbers found as limits within the game. For example, the lowest AC attainable on most machines is -128, because the AC value is stored in a signed 8-bit variable (schar) which can store up to 256 values: 127 positive numbers, zero, and 128 negative numbers. The lack of symmetry is due to the use of two's complement. An unsigned 8-bit variable would be able to store zero and 255 positive values.