ABSTRACT

This chapter explores what sort of instructions a computer can execute. The instructions in the instruction set are machine language instructions. Every different processor family has its own particular machine language, making machine language non-portable. The fact that machine language is numeric makes it somewhat difficult to work with, at least for human users. Data transfer operations move data from one location to another. Register-to-register instructions copy the data in one register to another register. Register-to-memory instructions copy the value of a register to a memory location. A memory-to-register instruction does the opposite of a register-to-memory instruction, copying from a memory location to a register. The device-to-register and register-to-device instructions move data to and from peripheral devices. Data manipulation instructions perform operations on data. On many machines, it is required that data being operated on is in registers. The integer data-type is used to represent whole numbers, meaning numbers that have no non-zero fractional part.