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9.2.2 Ambiguous conditions ¶

correct block read was not possible: ¶

Typically results in a throw of some OS-derived value (between -512 and -2048). If the blocks file was just not long enough, blanks are supplied for the missing portion.

I/O exception in block transfer: ¶

Typically results in a throw of some OS-derived value (between -512 and -2048).

invalid block number: ¶

-35 throw (Invalid block number)

a program directly alters the contents of BLK: ¶

The input stream is switched to that other block, at the same position. If the storing to BLK happens when interpreting non-block input, the system will get quite confused when the block ends.

no current block buffer for UPDATE: ¶

UPDATE has no effect.