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#### 9.25.3 PDP-11 Assembly Language Syntax

`as` supports both DEC syntax and BSD syntax. The only difference is that in DEC syntax, a `#` character is used to denote an immediate constants, while in BSD syntax the character for this purpose is `$`.

general-purpose registers are named `r0` through `r7`. Mnemonic alternatives for `r6` and `r7` are `sp` and `pc`, respectively.

Floating-point registers are named `ac0` through `ac3`, or alternatively `fr0` through `fr3`.

Comments are started with a `#` or a `/` character, and extend to the end of the line. (FIXME: clash with immediates?)