Mos12.mac is a very good facsimile of the Crystal Research MOS version 1.2 source code from 1984, but unlike the original it is in Microsoft M80 format.

The facsimile was created by firstly disassembling the ROM. Using a printed copy of the original all the labels were changed to their correct names then the equates and comments were added. 

The original uses macros for most of the RST routines, whereas the facsimile has fully expanded code and the macros are commented-out at the start of the file.

The facsimile uses DC statements for strings with the high bit of the last character set, whereas the original uses DB statements with 80H added to the last character.

The facsimile compiles using M80 and L80 in CP/M to create a binary image that is identical to the original MOS 1.2 ROM.

Mos12.prn is the listing file which contains the full source code of Mos12.mac and the corresponding addresses and byte values.
 
Tony Brewer