A group of instructions that gets a desired work done from the processor is known as instruction set. It is the set of machine code instructions that the processor can carry out. An instruction set is the part of computer architecture that is related to programming. An assembly instruction usually has three fields- OP code, destination and Source. Instructions can be classified into five functional categories. Control instructions are the instructions that perform the control operations and handle the overall program execution. On encountering Halt instruction, CPU finishes executing the current instruction and halts any further execution. Data transfer group consists of the instructions that transfer the data from one location to another. These instructions move data between registers, or between memory and registers.
Arithmetic group is a group of instructions that perform arithmetic operations on the data. Add instruction adds the content of the accumulator and the specified register or memory address. Sub instruction subtracts the content specified register or memory address from the content of the accumulator. Logical group is a group of instructions that perform logical operations on the data. Branch group a group of instructions that transfer the program sequence from one instruction to another. The branching instruction alters the normal sequential flow. The mode of representing the source and the destination address is called the addressing mode.