instruction code Val-Nand The instruction code 'Val-Nand' is an instruction code of the transsmt instruction set that computes the bitwise NAND logic operation on the values at the top of the ?B? and ?C? stacks. The result of this operation is pushed onto the top of the B stack. This instruction code can be modified by one or two 'Nop' instruction codes, which specify which stacks are used for computing the logic operation. Note that this is the only logic operation provided by the instruction set.