What are Instructions?

Learning Objectives Define what a computer instruction is and identify its fundamental components. Explain the difference between high-level code and machine-level instructions. Describe the basic steps of the Fetch-Decode-Execute cycle. Identify common types of instructions, such as arithmetic, data transfer, and control flow. Conceptualize how a sequence of instructions forms a program. Understand the role of the Program Counter in instruction execution. Have you ever wondered what really happens inside your computer when you click a button or run a program? 🤔 It all comes down to tiny, precise commands called instructions! In this lesson, we'll dive deeper into the fundamental building blocks of all computer programs: instructions. We'll explore what they are,...

TermDefinitionExample InstructionA single, atomic command given to the computer's central processing unit (CPU) to perform a specific operation.In a simplified view, 'ADD R1, R2' could be an instruction telling the CPU to add the contents of Register 1 and Register 2. Instruction SetThe complete collection of all the instructions that a specific CPU can understand and execute. Each CPU architecture (like x86 or ARM) has its own unique instruction set.An Intel Core i7 processor has a different instruction set than an ARM processor found in a smartphone. Machine CodeThe lowest-level representation of instructions, consisting of binary digits (0s and 1s) that the CPU can directly understand and execute.A machine code instruction might look like '0000000100000010' whi...

Instruction Format Rule Most instructions consist of an 'opcode' (operation code) and one or more 'operands'. The opcode tells the CPU *what* to do (e.g., add, move, jump), and the operands tell the CPU *where* to do it or *with what data* (e.g., specific registers, memory addresses, immediate values). Sequential Execution Rule Unless explicitly told otherwise, the CPU executes instructions in the order they appear in memory, advancing the Program Counter after each instruction. This rule ensures that programs run predictably from start to finish. Control flow instructions (like jumps or branches) are exceptions that alter this sequential flow. High-Level to Low-Level Translation Rule Every high-level programming statement (like `x = y + z;`) is tra...