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# The Assemblers
## <a id="pal-iii" name="pal3"></a>PAL-III
| **Introduced** | 1965
| **Introduced** | August 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 introduction date is for the earliest PAL-III manual I have found, but clearly we may extend it at least back to December 1964 based on the PDP-5 program catalog document. An [early PDP-5 brochure][pdp5b] I found from March 1964 speaks of a "Symbolic Assembler" rather than PAL; is that just marketing-speak, or does PAL first date to somewhere in that range?
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 also wanted a human-readable listing on the teletype.
The PAL-III 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 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.)
More importantly for our purposes here, most of the other assemblers surveyed here share PAL-III's basic syntax. This doubtless follows on from the prior point, since it meant PAL-III had the first-mover advantage.
A brief summary of the feature set of PAL-III:
* Full support of the PDP-8 instruction set:
* All basic processor instructions and several microcoded combinations (`CIA`, `SPA`, etc.) predefined
* Many peripheral IOT instructions predefined:
* auto-restart type KR01
* DECtape types 555 and TU55
* EAE options for PDP-5 and PDP-8
* high-speed punch/reader
* interrupt controller
* line printer type 645
* Core memory `FIELD` selection
* teletype/punch
* terminal keyboard/reader
* and many more less well-known peripherals!
* Define new instructions
* Zero-page addressing
* Indirect addressing
* Define new instructions
* Core memory `FIELD` selection
* `EXPUNGE`, `FIXTAB`, and `FIXMRI` pseudo-ops to redefine the predefined instruction set
* Radix selection with `DECIMAL` and `OCTAL` pseudo-ops
* `PAUSE` assembly output, giving the user time to do manual things while the assembler waits
We give this list not to try to replace its manual, but instead to allow searching this document for language features. You may assume that assemblers listed below also support these listed features, except where we say otherwise. Especially within the PAL genealogical line, compatibility with the baseline PAL-III syntax is assumed.
[pc5]: http://bitsavers.org/pdf/dec/pdp5/PDP-5_pgmLibr_1964.pdf
[pdp5b]: http://archive.computerhistory.org/resources/text/DEC/pdp-5/DEC.PDP-5.1964.102646094.pdf
[p83s]: http://www.ricomputermuseum.org/Home/equipment/pdp-8s/pdp-8-software
## <a id="macro-8"></a>MACRO-8
| **Introduced** | 1965
| **Introduced** | October 1965
| **Manual** | [PDF, 1.7 MB](https://www.grc.com/pdp-8/docs/MACRO-8_Programming_Manual.pdf)
| **Delivery** | paper tape
MACRO-8 was another paper tape assembler for the PDP-8. Its main advantage over PAL-III is that it added [macros](https://en.wikipedia.org/wiki/Macro_instruction), a very useful feature in assembly language programming as it reduces a lot of the tedium of writing such programs.
MACRO-8 is based on the PAL-III language, with several new features:
MACRO-8 is based on the PAL-III language, adding many new features:
* `DEFINE` macro definition system
* automatic off-page link generation
* literals in the current page via `(NN)` syntax or in page zero via `[NN]`; closing paren/bracket optional
* more operators in expressions:
* `!` for Boolean OR (the ASR-33 terminal character set [did not include the ¦ character][cs33])
* `DEFINE` macro definition system
* `&` for Boolean AND
* single-character ASCII constants: `"A`
* other new pseudo-ops:
* `DUBL`: ???
* `FLTG`: ???
* `DUBL`: define double-precision integer constant
* `FLTG`: define double-precision floating-point constant
* `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
The `DEFINE` feature is clearly this assembler's marquee feature, but it is the rest of the list that should open your eyes: all of these features except for `DUBL` and `FLTG` were later adopted as-is into the PAL family.
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.
> **Historical vignette:** Where the earlier PDP-8 assembler 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][ascii]: the United States of America Standard Code for Information Interchange; or the American National Standard Code for Information Interchange. You may also see "US-ASCII" in some places, being another way of writing "USA SCII".
**INCOMPLETE**
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* 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`
> **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.
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