Computer Instructions: Types of Operations

We can divide instructions into several type categories:

1. Arithmetic Operations (involving integers or floating-point numbers):
   • ADD: Adds up 2 or 3 numbers. Example: ADD R1, R2 to add the number in register R2 to the number in register R1.
   • SUB: Subtracts numbers. Example: SUB R1, X, Y to subtract the memory variables X and Y from register R1.
   • MUL: Multiplies numbers. Example: MUL X to multiply the variable X by a specific accumulator register.
   • DIV: Divides numbers. Example: DIV X, Y to divide the variable X by the variable Y, and store the result in X.
   • INC: Increments a number (= add $1$ to it.) Example: INC R1 to add $1$ to the register R1.
   • DEC: Decrements a number (= subtract $1$ from it.) Example: DEC X to subtract $1$ from the variable X.
   • NEG: Changes the sign of a number from positive to negative and vice versa. Example: NEG R2 to negate R2.

[Note that an instruction's name on one computer may differ from its name on another computer. E.g., a computer may call the multiplication instruction as MUL, MULT, or MULTIPLY: it depends on the decision of the computer's architecturers.]