3 characteristics of instruction
- collection of instruction is instruction set
- operation is determined by the instruction being execute
- each instruction must contain information required by processor to execute
4 element of instruction
- operation code
- source operand reference
- result operand reference
- next instruction reference
where the next instruction locate
main memory
where the source and result operand locate
- main or virtual memory
- I/O device
- CPU register
4 types of instruction
- data processing
- data storage
- data movement (I/O)
- program flow control
5 addressing mode
- immediate
- direct
- register
- register indirect
- implied
immediate addressing mode
data is specified and will be part of instruction
direct addressing mode
address of the data is specifies
- data will be in memory
register mode
specifies the name of register
register indirect mode
specifies the name of the register where address of data is available
- data will be in memory
- address will be in register pair
implied mode
instruction itself specifies data
3 uses of assembly language
- addresscritical performance issues
- access to specialised processor instruction
- direct hardware manipulation
4 advantages of assembly language
- speed
- space
- capability
- knowledge
LLL vs HLL
Low-Level-Language
- long sequence of instruction for complex task
- machine dependent
- know the internal structure of the microprocessor
High-Level-Language
- provide complex statement for complex task
- provide high level abstraction from the hardware details
- hide internal structure in instruction
RISC
- few instruction
- few addressing mode
- fixed length
- memory access limited to load or store instruction
- all operation done within register
- single cycle execution
CISC
- large number of instruction
- large variety of addressing mode
- variable length
- unfrequently used instruction for specified task
- manipulate operand in memory
