The instruction set architecture (ISA) is part of the processor
. It refers to the assembly language and how the programmer sees the behavior of the processor. The Instruction Set Architecture serves as a demarcation between the software and the hardware
. The instruction set architecture is characterized by certain features. These include the instruction set, and how the operands are processed and stored, the bit width supported by the ISA architecture, the number of registers, addressing, and how it handles interrupts.