1.8 KiB
1.8 KiB
| id | title | tags | created | ||
|---|---|---|---|---|---|
| iqh8 | Machine_code |
|
Monday, March 11, 2024 |
Machine code
No matter how a program was originally written, it eventually needs to execute on a CPU_architecture as a series of machine language instructions.
Example machine instruction
The following machine instruction is an instruction that would be understood by
an Instruction_set_architectures. It moves the number 4 into the
r7 register:
11100011101000000111000000000100
This 32bit line of binary has a series of instructions embedded within it. We partition each part of the sequence below, from left to right, mapping it to the instruction:
| Binary sequence | Instruction | Action |
|---|---|---|
| 1110 | condition | always execute (unconditional) |
| 00 | -- | -- |
| 1 | immediate | value is in the last 8 bits |
| 1101 | opcode | mov : move the value |
| 0 | -- | -- |
| 0000 | -- | -- |
| 0111 | destination register | destination is 0111 which means r7 |
| 0000 | -- | -- |
| 00000100 | immediate value | the binary representation of decimal '4' |
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The blank values are also instruction points, they are just not used in this instruction
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The instruction should run in all conditions not only under certain circumstances
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The immediate bit (
1) tells us