stem/CS/Code Types.md

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2023-05-20 01:33:56 +01:00
## Machine Code
- Machine language instructions
- Directly control CPU
- Strictly numerical
- Lowest-level representation of a compiled or assembled program
- Lowest-level visible to programmer
- Internally microcode might used
- Hardware dependent
- Higher-level languages translated to machine code
- Compilers, assemblers and linkers
- Not for interpreted code
- Interpreter runs machine code
- Assembly is effectively human readable machine code
- Has mnemonics for opcodes etc
## Microcode
- Layer between CPU hardware and instruction set architecture
- Normally written during design phase
- Deployed to ROM or PLA
- Programmable logic array
- Machine code often has some backward compatibility
- Microcode is circuit specific
## Byte Code
Portable Code
- Efficient execution by interpreter
- Compact numeric codes, constants and references
- Encode compiler output following analysis and validation
- Can be further compiled
- JIT
- Typically passed to VM
- Java, Python
## Object Code
- Product of compiler
- Sequence of statements
- Machine code
- Intermediate
- RTL
- Linked to form executable
- Object code portion of machine code not yet linked