This version of Call Now! is exactly 32 bytes long, including all the valid Oric Tape Headers. The source code is actually: 0LIST:.CALL NOW! I patched the value of the "." and replaced it by the value 0C which is the code to clear the screen, so the final binary is actually that: |---------- Header -------------------------------|-------- Program -----------|-- Footer --| 16 16 24 00 00 00 80 05 13 05 01 00 20 00 11 05 00|00 BC 3A 0C BF 20 4E 4F 57 C0|00 00 00 00 So the program is actually the follow sequence: 00 Line number BC LIST (instruction from BASIC) 3A : 0C Erase screen BF CALL (instruction from BASIC) 20 the space 4E 4F 57 NOW C0 ! What happens is that the program autoruns, encounters the LIST instruction, so it shows the source code on screen, then the C0 character deletes everything, and all that remains is the CALL NOW! message.