Everything related to BASIC version 1.x (Oric 1 and Atmos) or HYPERBASIC (Telestrat).
Don't hesitate to give your small program samples, technical insights, or questions...
The 1st instruction is a test to know if it's a ROM 1.0 or ROM 1.1 (it's the first byte that differs between the two ROMs).
#CC means ROM 1.1
You can consider that any test of a value in ROM (any address >= #C000) is to deetermine the type of ROM, as these values can't be changed by the user. Unless of course you are using the overlay RAM (which can't be done without an extension like disk drives).
EDIt: just realised you certainly needed an explanation for the whole code - sorry !
It's just a way to define a number of routines that will work on both the ATMOS and Oric 1.
Here are the values for the Atmos:
15005 DOKE#B000,#E76A - Set 6522 for cassette system
15010 DOKE#B002,#E93D - Reset cassette status
15020 DOKE#B004,634 - 27A - Address of first line of screen
15030 DOKE#B006,638 - 27E - Number of lines of text on screen
15035 DOKE#B008,#F88F - Reset ORIC
I think its not an universal code for every program to run in both roms.
It only modifies parameters located in #B000 - #B009 adresses. Probably tyrann machine code routine reads these memory locations to run explained rom routines when needed.