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A.1 Portable File Characters

Portable files are arranged as a series of lines of 80 characters each. Each line is terminated by a carriage-return, line-feed sequence (“new-lines”). New-lines are only used to avoid line length limits imposed by some OSes; they are not meaningful.

Most lines in portable files are exactly 80 characters long. The only exception is a line that ends in one or more spaces, in which the spaces may optionally be omitted. Thus, a portable file reader must act as though a line shorter than 80 characters is padded to that length with spaces.

The file must be terminated with a `Z' character. In addition, if the final line in the file does not have exactly 80 characters, then it is padded on the right with `Z' characters. (The file contents may be in any character set; the file contains a description of its own character set, as explained in the next section. Therefore, the `Z' character is not necessarily an ASCII `Z'.)

For the rest of the description of the portable file format, new-lines and the trailing `Z's will be ignored, as if they did not exist, because they are not an important part of understanding the file contents.