addressingmode

Addressing mode refers to the method by which the operand for an instruction is specified. In computer architecture, an instruction typically consists of an opcode and one or more operands. The addressing mode dictates how the CPU finds the actual data or memory location that the operand refers to. Different addressing modes offer varying levels of flexibility and efficiency for accessing data.

Common addressing modes include immediate addressing, where the operand's value is directly part of the instruction. Direct addressing uses a fixed memory address as the operand. Indirect addressing uses a memory address stored in a register or another memory location to find the operand. Register addressing uses the value held in a CPU register as the operand. Register indirect addressing uses a register to point to a memory location that holds the operand.

Other modes like indexed addressing add an offset to a register's value to calculate the operand's address, useful for accessing array elements. Based addressing combines a base register with an offset. Relative addressing calculates the operand's address based on the current program counter. The choice of addressing mode can significantly impact program performance and code size, and different architectures support a varying set of these modes.