Instructions (Computer Science)

A computer needs 1 instruction to run (OISC with subleq). It's possible but not fun.

Each instruction is of a fix size. In FISC, for example, each instruction is 2 bytes. Arguments on this instruction does not need to conform to a certain order (such as that dictated by the assembly language).

Operators

The ADD operator is very important. It is the fundamental building block of arithmetic operations such as subtract, multiply, divide, and modulo.

Suboperator

Some instructions have free bits in the instruction due to the fixed size. In this case, the free bits may be used as suboperators. This requires additional circuit on the ALU.

In FISC, for example, the not instruction only specify two registers (unlike the usual 3), so 2 bits are left free.