To study microprocessor, first we should have clear knowledge on what is a microprocessor ? The word microprocessor comes from the combination of micro and processor. Now as we know that processor means a device that processes whatever. But in reference to microprocessor study, processor means a device that processes numbers, specifically binary numbers, 0’s and 1’s. And we know micro means very small in size. So microprocessor as a whole a device which is small in size and process binary numbers.
So in definition we can say the microprocessor is a programmable device that takes in numbers, performs on them arithmetic or logical operations according to the program stored in memory and then produces other numbers as a result and send the result to output device or memory location.
So to work with a microprocessor we have to give proper instruction to microprocessor to work particular task. And those sets of sequential instruction as whole called program. The microprocessor can perform different sets of operations on the data it receives depending on the sequence of instructions supplied in the given program. By changing the program, the microprocessor manipulates the data in different ways.
Now question is what is instructions? Each microprocessor is designed to execute a specific group of operations. This group of operations is called an instruction set. This instruction set defines what the microprocessor can and cannot do. Like suppose we want to store data 02 in resistor B then the instruction will be in assembly language for 8085 microprocessor is MVI B, 02H. Here MVI means move immediate the data 02h to resistor B. Here 02h, H used for hexadecimal number.
Now some important terms we should know that the data that the microprocessor manipulates must come from somewhere. It comes from what is called “input devices”. These are devices that bring data into the system from the outside world. These represent devices such as a keyboard, a mouse, switches, and the like.