Questions Beginners Ask
Tom R Halfhill, Features Editor


Are you thinking about buying a computer for the first time, but don't know anything about computers? Or maybe you just purchased a computer and are still a bit baffled. Each month in this column, COMPUTE! will tackle some questions that we are asked by beginners.

Q When the new Atari 1200XL computer was announced a few months ago, Atari said it would be "software compatible" with the older Atari 400 and 800 models. Doesn't this mean that software which worked on the 400/800 should also work on the 1200XL? Then why won't certain cartridges for the 400/800 fit into the 1200XL's cartridge slot?

A To be fair, this isn't Atari's fault. But before we get to the cartridge question, let's define exactly what is meant by "software compatible," since this question is coming up frequently, too. And this definition applies to all computers, not just Ataris.
    Atari 400/800 software is upward compatible with the new 1200XL. This means that programs written properly for the 400/800 also will run on the 1200XL - although the reverse is not necessarily true. If a program is specifically written to take advantage of the 1200XL's special features (such as the HELP or special function keys, or the 64K of memory), it probably won't work on the 400/800 unless adjustments are made.
    But note that we said "properly written" software. Some programmers take shortcuts which can cause compatibility problems. Usually these shortcuts involve what are known as "illegal calls" to the computer's operating system. The operating system is a built-in program in all computers which does routine "housekeeping" tasks necessary to a computer's operation. Machine language programmers sometimes "call" routines built into the operating system to save themselves the trouble of writing similar routines. This is perfectly okay, except that these calls must adhere to certain rules to insure that the program will work on all future versions of the operating system. Atari's operating system manuals state that if these rules are obeyed, future compatibility is assured.
    That's why some machine language programs won't run on all versions of Ataris - the programmer took an unauthorized shortcut. Several popular commercial games were affected in this way when Atari revised the 400/800 operating system about a year ago. Late-model 400/800s have a "Revision B" operating system which fixes a few bugs in the old one. The changes were subtle, but some programs which depended on the old operating system were rendered unworkable.
    The 1200XL has a somewhat different operating system than the 400/800. Among other things, it includes the 1200XL's built-in diagnostics. Machine language programs for the 400/800 which call the operating system properly should have no trouble running on the new computer.
    Now, as for the cartridges: it's true that some Atari 400/800 cartridges made by independent software companies will not fit the 1200XL's slot. However, all cartridges made by Atari do fit. The slots are identical, except that the 1200XL has less room around the opening (the 1200XL's slot is external, while the 400/800 slot is beneath the front hatch). Some independent software companies made their cartridges oversized, which is why they won't fit a new slot.
    Probably these companies will issue new versions to fit the 1200XL. If you recently bought an oversized cartridge for a 1200XL, you may be able to exchange it. If you can't, the only solution is to take apart the cartridge. The "cartridge" is really just a protective plastic housing around a small circuit board. One screw or some glue usually holds it together. When the housing is removed, the board can be plugged into the slot. But do this only as a last resort, because it involves two dangers: (1) Exposed circuit boards are delicate and easily damaged by mishandling, and (2) if you accidentally manage to plug in the board upside-down, the board can be ruined. If you take apart a cartridge, we recommend clearly marking which side goes up (or forward in a 400/ 800), and fashioning some sort of protective cover out of cardboard or a flexible plastic cassette tape box.

Q I heard that Commodore recently introduced a new model computer called the "VIC-21," and that it is already being sold in some cities. What is the VIC-21? Why didn't we read about it ahead of time?

A Not to worry, we didn't let you down. There is really no such thing as a VIC-21- even though a store in Boston started selling them a few months ago.
    Confused? So were a lot of Bostonians. What happened is that a store began advertising a sale on the "VIC-21," which was really just an ordinary VIC-20 with a 16K memory expansion cartridge included. The package sold for about $200. As a promotion, the store pasted stickers on the boxes which said "VIC-21" - apparently derived from the sum of 16K plus the VIC's built-in 5K of memory. When people started calling competing stores and Commodore about the "new computer," Commodore immediately disavowed any connection with the promotion. Although it has been hinted that someday Commodore may upgrade the standard VIC, possibly with 16K, no such plans have been announced.