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e) The binary version number is ignored by the operating
system. It should be used to indicate the version number to
anyone examining the ROM.
f) The title string is printed out on selection of the ROM as a
language ROM. Apart from this, its only use is to identify the
ROM to those examining the ROM.
g) The version string is optional, and if it exists, it must be
preceded by a zero byte. It is only really of relevance to
languages, because on entry to a language the error pointer
(&FD and &FE) will point to this, or if not present, the
copyright message. ‘REPORT’ in BASIC demonstrates that
BASIC has no version string.
h) The copyright string is essential. This is because the ROM is
recognised by this string, and if it does not exist, the ROM will
be ignored. The format must always be a zero byte followed by
‘(C)’.
i) The tube relocation address, if present, indicates to the tube
system that the language part of the contents of this ROM have
been assembled to an address other than &8000. The address
given is the address to which the program must be copied in the
second processor. The service call code should still be
assembled into the &8000 space, because, for service entries, the
ROM is executed within the I/O processor.
15.1
Entering Paged ROMs
Paged ROMs are entered via one of three methods: by a service
call, via an extended vector, or through the language entry
point. Generally, a ROM should never be executed at all until it
has responded to at least one service call; the exception to this is
BASIC which has no service entry point. Always when within a
paged ROM, location &F4 contains the ROM number of the
ROM being executed.
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