| Inline Assembler

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GCC introduces a special `asm` keyword to support assembler instructions within C code. Roughly, its syntax is:

    asm ("instructions" [:output:input]);

The `asm` keyword may appear between usual lines of code or at the top level, outside of any function body. instructions may contain labels and references to global C symbols; in fact, the contents of the string are copied directly into the output file.

- Simple Inline Assembler Instructions
- Assembler Instructions with C Expression Operands
- Operand Constraints

If you are writing a header file that should be includable in programs compiled in GCC's strict ISO C mode, write `__asm__` instead of `asm`. See Alternate Keywords.