I always like the message, when a floppy disc screwed up, of "Retry, Abandon, Ignore, Salvage??" that CPM put up. The salvage option would copy the data from the disc, without the FAT (which was obviously screwed up) and put it onto another floppy disc, figure out and create a new FAT for it. MS DOS and DR DOS never had this facility!!
Also typing in CAT (Catalogue) instead of DIR to lisyt a disc's contents in CPM.
I can also remember when BIOS stood for Built In Operating System, as on the cover of the 1982 IBM publication "The IBM PC Built In Operating System Manual".
Somewhere, during the late 1980's, someone started wrongly calling it Basic Input Output System (which it is actually more than) and the worng label has stuck ever since.
I once won £20 at University over the true meaning of BIOS, during one argument. I just went with the guy to the Universty library, asked for the book (it was not a loan book) and just held it up, told the guy to read out aloud what the cover said, and held my hand out for the money.
I seriously need to find a copy of my own though, as I could travel around IT departments all over the planet making a living betting on the true meaning of BIOS!!
If you seriously need to programme a PC in assembler, you need access to this book. It has all the built in subroutines, operating proceedures, descriptions of pre-call register conditions and after call conditions/corruptions.
There are inbuild pieces of software, such as the XDPB, INT27, etc. that can be called upon to do work for you. Also data stream course changes can be performed by simply kicking an address with different value.
On all computers, by industry standards, Date Stream #1 is the Keyboard, #2 is the Printer, #3 is the VDU, #4 is the Serial Port, #5 is the Parallell Port, #6 and upwards relate to storage devices. By redirectiong a stream, you could type and what you type appears straight out of the printer port instead of ending up on screen.