Instruktionsuppsättning

Instruktionsuppsättning, often abbreviated as ISA, refers to the set of commands that a central processing unit (CPU) can understand and execute. It is the interface between the hardware and the software, defining the basic operations that the processor can perform. Think of it as the vocabulary and grammar of a CPU.

An ISA includes a collection of instructions, each with a unique opcode that specifies the operation to be performed, such as addition, subtraction, data movement, or logical operations. It also defines the format of these instructions, including how operands (the data the instructions operate on) are specified. Operands can be registers within the CPU, memory locations, or immediate values embedded directly in the instruction.

Different CPU architectures have different instruction sets. Common examples include the x86 architecture used in most personal computers and the ARM architecture prevalent in mobile devices. The choice of ISA impacts the complexity of the CPU design, the performance of software, and the power consumption. A complex instruction set computer (CISC) has a large and varied set of instructions, while a reduced instruction set computer (RISC) has a smaller, simpler set. Software written for one ISA generally cannot run directly on a CPU with a different ISA without translation or emulation.