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| **Introduced** | 1965
| **Manual** | [PDF, 790 kB](http://www.telegraphics.com.au/doc/paliii.pdf)
| **Delivery** | paper tape
We may presume from the name that PAL-III has two predecessors. I was able to find a reference to DEC product number 5-1-S, the Program Assembly Language for the PDP-5, which the PDP-8 directly replaced in DEC's product line, being upward compatible with it. That same [PDP-5 program catalog][pc5] says that its replacement is [an early version of PAL-III][p83s]. I have not been able to find a reference to PAL-II. Perhaps it went the way of Angular 3, Winamp 4, Netscape 5, PHP 6, MySQL 7, QuickTime 8, and Windows 9.
The PAL-III assembler shipped on [punched paper tape](https://en.wikipedia.org/wiki/Punched_tape) as part of the grandiosely-named "PDP-8 Assembly System." This amounted to an assembler, an editor, a debugger, and a loader, each a separate paper tape. The programmer would first toggle the RIM loader into the PDP-8's front panel, then use that to load the BIN loader from yet a fifth paper tape, then run each of these tapes through the paper tape reader repeatedly — reusing the still-in-core BIN loader each time — in order to iterate his way toward a working program!
The PAL-III assembler shipped on [punched paper tape](https://en.wikipedia.org/wiki/Punched_tape) as part of the grandiosely-named "PDP-8 Assembly System." This amounted to an assembler, an editor, a debugger, and a loader, each a separate paper tape. The programmer would first toggle the RIM loader into the PDP-8's front panel, then use that to load the BIN loader from a fifth paper tape, separate from the PDP-8 Assembly System, then run each of these tapes through the paper tape reader repeatedly — reusing the still-in-core BIN loader each time — in order to iterate his way toward a working program!
The assembler tape required at least two passes through the tape reader in order to produce a computer-readable BIN format output tape, plus an optional third pass if you wanted a human-readable listing on the terminal.
The assembler tape required at least two passes through the tape reader in order to produce a computer-readable BIN format output tape, plus an optional third pass if you also wanted a human-readable listing on the teletype.
If you look at pictures of PDP-8 computers, you can often see a tray with narrow slots in it, each meant to hold one of these key paper tapes, as they were needed near at hand when using the computer. There is a good picture of a blue one on [the cover of the 1974 edition of the OS/8 Handbook](https://archive.org/stream/bitsavers_decpdp8os8_39414792/OS8_Handbook_Apr1974?ui=embed#page/n0/mode/1up).
If you look at pictures of PDP-8 computers, you can often see a tray with narrow slots in it, each meant to hold one of these key paper tapes, as they were needed near at hand when using a paper-tape based PDP-8. There is a good picture of a blue one on the cover of the [OS/8 Handbook][os8m], 1974 ed.
PAL-III can be considered the baseline assembler for a PDP-8, since for roughly its first decade, PDP-8s sold for interactive use came with a Teletype Model 33 ASR with built-in paper tape reader and punch, which meant the ability to read paper tapes was a baseline feature for interactively-used PDP-8s. (Contrast headless embedded PDP-8s, a very common use for the PDP-8 prior to the introduction of the microprocessor.)
PAL-III can be considered the baseline assembler for a PDP-8, since almost every PDP-8 at least included some kind of paper tape reader, and most of the other assemblers surveyed here share its basic syntax.
We will not list the feature set of PAL-III here; see its manual for that. The lists of features in the sections below are relative to either PAL-III or one of the other assemblers reviewed below. Within the PAL genealogical line, compatibility with the baseline PAL-III syntax is assumed unless a note is made otherwise.
* The `DEFINE` based macro definition system
* Other new pseudo-ops:
* `DEFINE` macro definition system
* other new pseudo-ops:
* `DUBL`: ???
* `FLTG`: ???
* `PAGE`: [re]set the location counter to the top of the given page
* `TEXT`: convert a literal string in the program text to 6-bit packed ASCII in the binary output
MACRO-8 dropped the `FIXMRI` pseudo-op relative to PAL-III. One manual I examined showed an example that could only be done using `FIXMRI` under PAL-III, by which I infer that MACRO-8 simply doesn't need the hint from the user: memory reference instructions can be detected as part of regular symbol table manipulations.
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| **Manual** | [PAL-D Disk Assembler Programmer's Reference Manual](https://archive.org/details/bitsavers_decpdp8sofProgRef_1907666)
| **Delivery** | paper tape
PAL-D is a descendant of PAL-III, originally appearing as part of the [PDP-8 Disk Monitor System](https://en.wikipedia.org/wiki/4K_Disk_Monitor_System), one of OS/8's predecessors. It would later reappear under TSS/8.
PAL-D came in two forms, the 4K and 8K versions, referring to the minimum amount of core memory each required. Note that the 4K version could assemble for larger machines; it has the `FIELD` pseudo-op, for example, which is of no use unless your assembled program would run in at least 8K of core.
The 4K version defines only one new feature in the PDP-8 assembler family so far: the `XLIST` pseudo-op, which lets the programmer stop and then re-start the assembly listing in the optional third pass. The 4K version is more notable for the features it brought into the PAL family from [MACRO-8](#macro-8): the `PAGE` and `TEXT` pseudo-ops.
8K PAL-D added quite a few new features over the 4K version:
* ability to run in 8K or 12K of core, allowing assembly of larger programs
* automatic link generation for off-page references
* literals
* off-page link generation
* the `PAGE` and `TEXT` pseudo-ops
* more operators in expressions:
* `!` for Boolean OR (the ASR-33 terminal character set [did not include the ¦ character][cs33])
* `&` for Boolean AND
8K PAL-D added several more features relative to the 4K version:
* ability to run in 8K or 12K of core, allowing assembly of larger programs
* single-character ASCII constants: `"A`
* more pseudo-operations:
* `EJECT`: emit a form feed in the listing output
* `IFDEF` and `IFZERO`: conditional assembly tests; affected statements in angle brackets
* `NOPUNCH` and `ENPUNCH`: stop and restart assembled machine code output
* `ZBLOCK`: reserve memory, setting initial values to zero
Note that neither version of PAL-D brought over the `DEFINE`, `DUBL` or `FLTG` pseudo-ops from MACRO-8.
Notice also that the negated forms of the conditional assembly operations did not appear until later. The first reference I've been able to find for `IFNZRO` and `IFNDEF` is in connection with [PAL8](#pal8).
We find evidence for a complicated development history in the `PUNCH` and `XLIST` pseudo-ops. They do much the same thing, only for different passes of the assembler, yet the form of the ops differ. If this assembler was created by a single mind in a single time and place, or if it were created by a standards committee with a mandate to simplify and unify, you would expect these two sets of pseudo-ops to have similar names and forms, either `XPUNCH` taking an argument or a `NOLIST`/`ENLIST` pair. We can infer different minds behind the 4K and 8K versions of PAL-D.
The `PUNCH` op names also suggest that the operation is mainly useful for paper tape output, still an important I/O device when PAL-D was new. We can find it mentioned in the PAL8 section of [the OS/8 Handbook (1974 ed.)][os8m], but it was airbrushed out of history by the [1979 edition for OS/78][os78m], suggesting that the purpose of these pseudo-ops became effectively redundant after the bulk of the market moved to disk-based PDP-8 systems such as the [DECstation 78][ds78], a microcontroller based PDP-8 merged with a VT52 video terminal, which effectively replaced the teletype + paper tape reader/punch most often used with earlier PDP-8 systems. (Thus the renaming of "OS/8" to "OS/78," by the way.)
Like MACRO-8, PAL-D does not have the `FIXMRI` pseudo-op.
> **Historical vignette:** When these manuals refer to the new ASCII character constant feature, they actually either refer to "USA SCII" or to "ANSCII", those being the original names of ASCII: the United States of America Standard Code for Information Interchange; or the American National Standard Code for Information Interchange.
[cs33]: http://iclces.uk/articles/a_teletype_font.html
[ds78]: https://en.wikipedia.org/wiki/DECstation#DECstation_78
## <a id="os8"></a>The OS/8 Assemblers
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