Radio Shack TRS-80 Model II Reference Manual page 79

Library Commands
Sample Uses
When updating a file, it is a good practice to input from the old file and output
updated information to a new file. That way, if the update is wrong, you still
have the old file as a backup. When you have verified that the update file is
correct, you can Kill the old file.
KILL
is also useful in conjunction with pre-allocated files. Suppose you have
finished writing to a pre-allocated file, and one or more granules are unused
in the pre-allocated file. Then you can copy the pre-allocated file to a
dynamically allocated file, and afterwards Kill the pre-allocated file. This is
the only way to reduce the size of a pre-allocated file.
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