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PAL8 understands the same basic language as PAL-III and generally has more features, most especially related to running under OS/8, such as the ability to set options via OS/8's command interpreter (CCL) rather than via the PDP-8's front panel switches.
I consider it the default assembler for OS/8 users. If none of the information below guides you to one of the other assemblers, you should probably start with PAL8. If you have a piece of assembly code that is meant to be assembled under OS/8, and you have no evidence that is for any other assembler, it's probably meant to be assembled by PAL8.
PAL8 has many features not present in PAL-III:
* automatic link generation for off-page references
* it can output [CREF and DDT][os8m]-compatible output files
* output options for [CREF and DDT][os8m]
* in addition to `+` and `-` in expressions, it allows:
* `^` for 12-bit unsigned multiplication (`*` was already taken for setting the location counter)
* `%` for 12-bit unsigned division (`/` was already taken as the comment start character)
* `!` for Boolean OR (the ASR-33 terminal character set [did not include the ¦ character](http://iclces.uk/articles/a_teletype_font.html))
* `&` for Boolean AND
* literals in the current page via `(NN` syntax (closing paren optional) or in page zero via `[NN`
* single-character ASCII constants: `"A`
* more pseudo-operations:
* `DEVICE`, `FILENAME`, and `TEXT`: insert 6-bit packed ASCII text strings in the output
* `DTORG`: set DECtape block number in typesetting output
* `EJECT`: emit a form feed in the listing output; optionally set a new header line
* `IFDEF`, `IFNDEF`, `IFZERO` and `IFNZRO` with angle brackets for conditional assembly
* `PAGE`: [re]set the page part of the location counter
* `NOPUNCH` and `ENPUNCH`: stop and restart binary output
* `RELOC`: assemble code for relocation after loading
* `XLIST`: suppress part of the listing output
* `ZBLOCK`: reserve memory, setting initial values to zero
PAL-III has a few features not implemented in PAL8:
* the ability to get a brief listing of the undefined symbols in a program
The latter is the more important lack. The information is instead presented inline in the listing output, not grouped together into a single place, which can make refinement of an in-development program tedious as you need to comb information about undefined symbols out from among all the other output.
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