DEC              Decrement                           Flags: O D I T S Z A P C
*       * * * *
DEC destination

Logic:    destination   destination - 1

This instruction decrements the destination by one. The destination
operand, which may be either a word or a byte, is treated as an
unsigned binary number.

                                                                          
Operands                  Clocks   Transfers  Bytes   Example
reg16                       2          -        1     DEC BX
reg8                        3          -        2     DEC BL
memory                 15(23) + EA     2       2-4    DEC MATRIX[SI]
                                                                          

Note:          This instruction does not set the carry, so if you
need to decrement a multi-word number, it is better
to use the SUB and SBB instructions.

See also: SUB
See also: SBB
See also: AAS
See also: DAS
See also: EA
See also: Flags

DEC Decrement