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The Cass Code

gp2000

gp2000

Experienced Member
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Vancouver, BC, Canada
The first thing a Model III or Model 4 does when booting into ROM BASIC is give you the Cass? prompt. Did you know there are 3 subtle variants on the prompt? Each has different spacing around the question mark. I'll use underscore for the cursor to illustrate:

Code: 
1. Cass? _
2. Cass ? _
3. Cass ?_

Variant 1 is on all Model III's. Variant 2 is on Most Model 4's. Variant 3 is used on late/international Model 4's and all Model 4P's.

It feels like an intentional version signifier but at this remove who can tell. It could be down to programmers not paying close attention or using their own preferred spacing convention.
 
Neat observation. I vote that it was a version indicator because that’s a cool story and plausable.

One wonders what they would have done on the Model 5? “Cass?_” ?
 
If years of corresponding with Frenchmen on the Internet have taught me anything, it's that popular French orthography insists on a (non-breaking) space between the last letter of a sentence and any terminal punctuation that is not a period. So the prompt might have been "corrected" by people doing localized versions?
 
pski said:
Neat observation. I vote that it was a version indicator because that’s a cool story and plausable.

One wonders what they would have done on the Model 5? “Cass?_” ?
Click to expand...

If they'd made a Model 5 I wouldn't have been surprised if there wasn't a cassette interface.
 
vwestlife said:
My U.S. model Tandy 4D (serial number 000491) shows variant 3 ("Cass ?_").
Click to expand...

This would be expected if what the Northern Bytes articles say is true.

Northern Bytes Volume 6, #2:

This article is a not-too-well organized collection of data on the differences between the "old" and "new" versions of the Model 4 ROM/4P ROM image (that is used when the computer is run in the "Model III mode"). The "new" version was first introduced in the Model 4P ROM image (the "MODELA/III" file supplied with the 4P), then copied back to the "un-portable" Model 4 at about the same time that Radio Shack relocated the arrow keys and started putting green CRT's in the 4 and 4P. The "new" Model 4 ROM and the "new" 4P ROM image have a few minor differences, mostly due to hardware.
Click to expand...

Northern Bytes Volume 6, #3:

The Model III ROM is actually three ROMs. ROM A holds the contents of addresses 0000 to 1FFF (all values given in hexadecimal), ROM B contains 2000 to 2FFF, and ROM C has 3000 to 37FF. There have been several versions of ROM C, but recently, for the first time since the Model III was introduced, Radio Shack has changed ROM A.... The only major change is the printer driver (the interface between the computer and a parallel printer), although there are several minor changes elsewhere.
...
...mentions that LDOS Support, commenting on the text file, said that the ROM A described in the file is what Radio Shack calls the "international ROM". This ROM A, together with the appropirate ROM C for the target country, has been distributed on Model 4's shipped to foreign markets ever since the earliest days of the Model 4. Apparently they have just decided to use this ROM A domestically also.
Click to expand...

One of the changes in the new ROM is a routine to download code from the RS-232. It appears that routine was added for the Model 4 Student Station so I'm curious if your Model 4D ROM contains the same RS-232 boot code.
 
Alphasite said:
If they'd made a Model 5 I wouldn't have been surprised if there wasn't a cassette interface.
Click to expand...

You raise I point I hadn't thought about. The Model 4P ROM file still includes the cass prompt even though the 4P itself has no cassette hardware. I imagine it was left in to avoid unnecessary changes and keep the Model III compatibility mode familiar to Model III users. Though you would have a heck of a time getting programs in and out of ROM BASIC if it was booted in cassette mode.
 
gp2000 said:
You raise I point I hadn't thought about. The Model 4P ROM file still includes the cass prompt even though the 4P itself has no cassette hardware. I imagine it was left in to avoid unnecessary changes and keep the Model III compatibility mode familiar to Model III users. Though you would have a heck of a time getting programs in and out of ROM BASIC if it was booted in cassette mode.
Click to expand...

I think a Model 5 would also be similar to the 4P in that you'd need to load a Model III ROM image if you wanted to run Model III software.
 
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