# Assembly Language Basics Assembly language is a low-level programming language that corresponds directly to the architecture of a specific CPU. In essence, it's a symbolic representation of machine code, which the CPU can execute directly. ## Instructions and Operands An assembly language program consists of instructions, each of which performs a specific operation. Instructions consist of an operation code (opcode), and zero or more operands. Operands can be constants, register names, or memory addresses. Here's an example of assembly code, taken from the x86 architecture: ```assembly mov eax, 1 add eax, 5 ``` In the above code, `mov` and `add` are opcodes. `eax` is a register, and `1` and `5` are immediate operands (constants). ## Memory Addressing Assembly language supports several modes of memory addressing, including direct, indirect, and indexed addressing. Direct addressing involves specifying the memory address directly as an operand. For example: ```assembly mov eax, [2000] ``` This instruction moves the value at memory address 2000 into the `eax` register. ## Registers Registers are small storage areas directly inside the CPU. They hold data that the CPU needs to process. Each CPU architecture has its own set of registers, with their own names and purposes. For example, in the x86 architecture, the `eax` register is often used to hold the result of an operation. ## Control Flow Assembly language supports conditional and unconditional branching, which allows the creation of complex control flow structures. For example, the `jmp` instruction can be used to implement loops: ```assembly mov ecx, 5 start: dec ecx cmp ecx, 0 jne start ``` This loop will run 5 times. In conclusion, assembly language provides a powerful and flexible way to program CPUs at a low level. It requires a deep understanding of computer architecture, but offers unparalleled control over the hardware.