ARM-Instruction-Set - Using as
Description: Using as

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##### 9.3.2.1 Instruction Set Syntax

Two slightly different syntaxes are support for ARM and THUMB instructions. The default, `divided`, uses the old style where ARM and THUMB instructions had their own, separate syntaxes. The new, `unified` syntax, which can be selected via the `.syntax` directive, and has the following main features:

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  Immediate operands do not require a `#` prefix.
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  The `IT` instruction may appear, and if it does it is validated against subsequent conditional affixes. In ARM mode it does not generate machine code, in THUMB mode it does.
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  For ARM instructions the conditional affixes always appear at the end of the instruction. For THUMB instructions conditional affixes can be used, but only inside the scope of an `IT` instruction.
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  All of the instructions new to the V6T2 architecture (and later) are available. (Only a few such instructions can be written in the `divided` syntax).
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  The `.N` and `.W` suffixes are recognized and honored.
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  All instructions set the flags if and only if they have an `s` affix.