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Using stdin to input source code to the assembler
You can use stdin to pipe output from another program into armasm or to input source code directly on the command line. This is useful if you want to test a short piece of code without having to create a file for it.
Built-in variables and constants
The assembler defines built-in variables that hold information about, for example, the state of the assembler, the command-line options used, and the target architecture or processor.
Conditional assembly works differently from conditional compilation using the C preprocessor.
Using the C preprocessor
The assembler can invoke the compiler to preprocess an assembly language source file before assembling it. This allows you to use C preprocessor commands in assembly source code.
The handling of unaligned addresses in load and store instructions depends on the ARM architecture version.
Instruction width selection in Thumb
If the assembler can select either a 16-bit or a 32-bit encoding for a Thumb instruction, in general it selects the 16-bit encoding. You can override this by specifying a .W or .N mnemonic qualifier.