The hex files used as input to the final version of the Z80 simulator have the
following format:

Column 1       Ignored (generally blank)
Column 2       # character
Column 3-6     Four hex digits specifying a 16 bit load address high byte first.
Column 7-102   Between 2 and 96 hex digits specifying code to load starting at the above address.
Column 103     & character
Column 104-105 Two hex digits specifying an 8bit checksum.

The number of hex digits in columns 7-102 must be even. If there are less than 96
hex digits in columns 7-102, the & character and checksum digits follow immediately
after them and the record is less than the maximum 105 bytes long.

The checksum is chosen such that a mod 256 sum of all the pairs of hex digits in
a given record including the checksum is zero. However, the checksum is not
actually verified by the Z80 simulator.

A $ character on its own in column 2 will terminate the program as will end of file.


The initial WATFIV version of the Z80 simulator uses a simpler file format. Records
are all at least 72 bytes long and each consist of twenty four two digit hex numbers
separated by spaces. Code is always loaded at address zero. The program file is called
"P" unless changed in the /FILE 10 statement at the beginning of the program.