Instruction Set Architecture (ISA)
Machine Level Instruction Set Architecture (ISA):
• This level froms the interface between hardware and software.
• This makes it possible to execute program written in different higher level languages. The programs are translated to ISA level and the hardware can then execute them.
• This, ISA level defines the interface between the compiler and the hardware. It is language that both of them have to understand.
• The higher level programs are compiled to an ISA program. Then this is executed by micro program or hardware.
• An instruction set ,or ISA is a part of the computer architecture related to programming, including the native data type, instructions, registers, addressing mode, memory architecture, interrupt and exceptional handling, external I/O.
• An ISA includes a specification of the set of opcodes, the native commands implemented by a particular CPU design
Example:An operation ADD is a part of instruction set stored in a memory. It is a binary code that tells computer to perform an ADD operation.
• CU decodes instructions from the memory. Then an issue a sequence of control signal to initiate microoperation in internal computer register.