ASM.CAS is the PolyMorphic assembler

ASMP.CAS is the assembler patched to use the printer port at 2400 baud for
    cassette load and save (use the "BYTE" format of load and save commands)

Naming Convention is to start the source file name with the letter "A"
  ALISTR is the source file for the executable LISTR
  ATPERR is the source file for the executable TPERR