46 lines
1.4 KiB
Markdown
46 lines
1.4 KiB
Markdown
---
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id: 2v5c
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title: Assembly
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tags: [CPU]
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created: Tuesday, March 12, 2024
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---
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# Assembly
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- Assembly is one level up from machine code and provides a more human-friendly
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abstraction layer
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- An assembly instruction is a _mneumonic_ that comprises an "op code" plus
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operands
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- It is translated back to machine code by an assembler for the computer to
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execute.
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## Example instruction
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We can translate the machine instruction `e3a07004` into the assembly
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instruction `mov r7, #4`. This translates to: _move the value number 4 to the
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register r7_.
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## Assemblers
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Although assembly is useful for humans, computers still work at the level of
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machine code. Therefore you need an **assembler** to translate the assembly code
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to machine code. An assembly language text file is fed into an assembler and a
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binary object file containing machine code is returned.
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A disassembler does the opposite: translate machine code into assembly.
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## Relation to instruction set architectures
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- the ISA defines the hardware capabilities and the instructions that can be run
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on the hardware
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- machine code is a binary representation of these instructions and can be
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directly executed by the CPU
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- humans use an assembly language version of the machine code which is then
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translated back to machine code for the computer to execute.
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## Related notes
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[[Hexadecimal_number_system]], [[Instruction_set_architectures]],
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[[CPU_architecture]]
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