Software Engineering Computer Architecture Instruction Set Architecture (ISA) Course

Computer Architecture
Instruction Set Architecture (ISA)

,Instruction Set
• The basic elements a processor performs is an “instruction”
• The group of instructions the processor can perform is called “instruction set”
• The “instruction set” is the interface between the designer of the processor and the
programmer of the processor
• The programmer needs to understand the instruction set in order to program the proces
• The designer needs to understand it as well, but in order to correctly implement a proces
that performs them
• The term “Instruction Set Architecture” refers to that part of the processor that the
programmer needs to be aware of in order to be able to program the processor

,Instruction Set Architecture
• The instruction set architecture of a processor includes the followin
elements:
• Registers
• Instructions (as well as op-codes)
• Addressing modes
• Memory architecture
• Interrupt handling
• I/O handling

, Instruction Set Architecture
• Instructions and op-codes
• Instructions must be translated into machine code binary equivalent for the processor to
understand them
• The tool that translates the instructions is the “assembler”
• Op-codes are the part of the machine code that identify the instruction
• Op-codes inform the control unit what operation we want the processor to do
• Op-codes require other set of information to work, namely:
• Source operands/memory address
• Destination operands/memory address
• Immediate data
• We will see examples for instructions and how they are packed into their machine code
equivalents later (instruction format)