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§20.2. Memory limitations
Inform creates "story files" for very small virtual computers (capable of running on phones, for instance) where memory is tight. If we create a number variable and keep on adding 1 to it, the value simply gets bigger. But if we make some text and keep on adding a letter "x" to it, the text takes up more and more space, growing into longer and longer runs of "x"s until there is no more space to hold it.
The following warnings are rather like the tiny print about side-effects on medicine bottles: that is, we mostly ignore them, and if the drugs should kill us, well, at least we have the consolation of knowing we were warned. There are basically three limitations on text:
(1) An amount of memory has to be set aside for text (and other flexible-sized data), and Inform guesses the amount needed. Story files using the Glulx format (see the Settings panel) are able to increase this as necessary in play, so there's no problem if the guess was wrong. But Z-machine story files are stuck with whatever amount of memory was initially chosen.
That choice can be increased with a use option, like so:
Inform raises its estimate of the amount needed to ensure that this amount is always at least its own guess, and also at least any amount declared like this. (And then it rounds up to the nearest power of 2, as it happens.) The default value of "dynamic memory allocation" is 8192. In practice, this use option isn't needed much, though, because any story needing large amounts of dynamic memory will likely be on Glulx in any case.
(2) Text has a maximum length. This maximum is normally 1000 characters, which ought to be plenty, but can be raised by sentences such as:
What happens if this is broken, that is, if we try to use text overrunning this length? The Z-machine may simply crash, so if there is any chance that any single text may grow unpredictably large, Glulx should always be used. On Glulx, overrunning text is truncated safely, except that under Glulx 3.1.0 or better the story file will try to use dynamic memory allocation to expand the limit as needed to avoid truncation. (Testing shows that text is slow to manipulate once it grows beyond about 20,000 characters in length, but this is not really surprising.)
(3) Under the Z-machine, text may only contain characters from the so-called "ZSCII" character set - standard numbers, letters, punctuation marks and the commonest West European accented letters. Anything more exotic is likely to be flattened into a question mark "?". Under Glulx, any character can be used.
All of this makes the Z-machine sound very inferior, for text purposes. But note that Z can handle all of the examples in this chapter perfectly happily.
