Infocom and the IBM PCjr

The PCjr was my family’s first computer, and it was the machine I played all my early text adventures on. I recently bought a PCjr off eBay and I still had my original disks from the 1980s, so I inserted them and booted them. The Infocom disks ones still work!

Here is something I didn’t know: this PCjr I got from eBay came with 128KB of RAM. Zork and Zork II start in 40 column mode. The text is bold, crisp, large and quite readable.

Last night, I installed a modification board to the PCjr to get it to 640KB of RAM. Zork II (only one I have re-tried so far) now comes up in 80 column mode. Who knew? I have to assume that it’s the extra RAM that allows it.

I’m curious if anyone else has memories of this sort of thing going on. There are wild little eccentricities that I’ve been seeing as I pop Infocom games into various retro systems - for instance, I have an Apple //c next to me that runs Enchanter in an all-capital-letters mode. Perhaps it did that for all games, I am not sure. But the 40/80 column thing being auto-detected for the PCjr really surprised me, if that is in fact what is going on.


Fascinating. Are these DOS discs, running the games in AUTOEXEC.BAT, or do they boot a custom loader?


When you boot this disk, does it ask if you want to use 80 columns? The Apple II series only got 80 columns and lower case characters as a default when the Apple IIe came out. Your IIc is newer than that. But to keep the games compatible with earlier Apples like the II+ with the smallest technical outlay on their end, I think they treated 40 column mode as “old computer mode”. So if you play in 40 columns, it’s always all caps, even on Apple IIs that can show lower case letters.


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My sister worked at IBM, so she owned one and my younger brother had one, both of which had copies of Infocom games.

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Indeed is a curious behavior, similar, and perhaps IS the same design logic, of the Apple ZIP, but the choice of screen is unusual.

The question of Nathan matters, that floppy is a booter (that is, NOT booting into DOS) or not ? from the Wikipedia list, for what matters (see here) we have:

Cutthroats 	1984 	Interactive fiction 	Infocom
Deadline 	1982 	Interactive fiction 	Infocom
Enchanter 	1986 	Interactive fiction 	Infocom
The Hitchhiker's Guide to the Galaxy 	1984 	Interactive fiction 	Infocom
Infidel 	1983 	Interactive fiction 	Infocom
Planetfall 	1983 	Interactive fiction 	Infocom
Seastalker 	1984 	Interactive fiction 	Infocom
Sorcerer 	1984 	Interactive fiction 	Infocom
Starcross 	1982 	Interactive fiction 	Infocom
Suspect 	1984 	Interactive fiction 	Infocom
Suspended 	1983 	Interactive fiction 	Infocom
The Witness 	1983 	Interactive fiction 	Infocom
Zork: The Great Underground Empire 	1982 	Interactive fiction 	Infocom
Zork II: The Wizard of Frobozz 	1983 	Interactive fiction 	Infocom
Zork III: The Dungeon Master 	1984 	Interactive fiction 	Infocom 

and a booter game, esp. those of 1983/4 vintage (when the compatibles, but not all those 100% clone from Taiwan, was around), the booter and the 'terp doing prudent assumption on the hardware, in absence of DOS and its interrupts and variety of compatible BIOS was good coding practice back then. so it’s a thing whose indeed piqued my interest, but NOT enough interest to delve in the hell of disassembling 8086/88 binaries (death to segments and offsets !!)

of course, Robb, you should check the release and “serial” number against Zarf’s obsessively complete list, in the case you happen to hold an unknown or lost release…

Best regards from Italy,
dott. Piergiorgio.

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I don’t have my books on old PC video hardware here to verify it, but according to Wikipedia the 40 columns text mode takes only 1 Kb of system memory, so maybe it was memory pressure that forced the issue. Having said that, I have faint memories of playing some Infocom games in 80 column mode on an original 64Kb IBM PC at school, but on the PC the video memory was on the graphics card. (Also there were some 128Kb XTs available, and some with MDA graphics card, so this may not mean anything).


Fascinating. Are these DOS discs, running the games in AUTOEXEC.BAT, or do they boot a custom loader?

In my case, I was using a couple of Infocom disks with a custom bootloader.

I think I have more data on what is going on. Originally, the PCjr I have had 128KB of memory - everything started in 40 column mode.

I installed a hardware mod to get it to 640KB, and now everything is defaulting to 80 columns - Infocom games included. So I think this is a characteristic of the PCjr itself, and nothing Infocom was doing. I have some more comments and replies that I will ASAP.

This is an interesting question! The Infocom Fact Sheet lists various version numbers for Infocom interpreters (IBM, Amiga, Atari ST, and MAC) but does not address the question of 40 v 80 column support AFAIK.

On a related note, I have always wondered when the C64 'terp was upgraded to feature lower case letters, a new white-on-gray color scheme, and a clicking sound to complement key presses (C64 never supported 80 columns, but C128 did). I don’t think it corresponded to the gray box standardization. IIRC my first game with this fancy new interpreter was Hitchhiker’s Guide to the Galaxy.

Are feature sets of in-house interpreter upgrades documented anywhere? I suppose that would be a big job considering the number of supported platforms.

Didn’t the C64 versions always have lowercase text? As I recall the earliest releases were done jointly with Commodore, in Commodore specific packaging, and these were the ones that used the default light blue on blue colour scheme. I don’t think I’ve ever come across C64 folio releases, and all the grey box C64 releases I’ve had were all the white on grey colour scheme.

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I have looked into GB64’s database of screenshots and I must note a third colour scheme, white on black, all dated (by serial #, the screenshot being readable even in thumbnail size) 1987-88, the white on grey are dated 1982-1987, the majority 1984-5 and the default light blue on blue are dated 1982-1983, with a solitary 1984 serial (Sorcerer R4-840131)

Best regards from Italy,
dott. Piergiorgio.

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The CBM release deal spanned from Zork I though Suspended (early 1983), and Infocom did folio releases for the remaining five folio games (Witness through Sorcerer) on C64. Additionally, some reprint runs must have fallen outside of the CBM contract. I owned a Deadline C64 folio, despite an earlier CBM release.

All games up to Sorcerer initially released with all caps and the C64 default system colors.

Perhaps I have misremembered. This would match the timing of Infocom’s migration to the gray box format. Sorcerer was only briefly in print as a folio game, which makes its original feelies (the infotater wheel in particular) quite rare.

I actually own Starcross, Suspended, and Deadline in the CBM packaging. I like them more than their gray box equivalents!

E: interestingly, some CBM releases had bilingual (English and French) manuals, which I don’t think occurred with any other versions of Infocom games.