The BBC and Master Computer Public Domain Library

BBAC Initialise Page 7 & reset Variable pointers, etc...

Submitted by Steve Fewell

Description:

Set LOMEM and VARTOP to TOP [end of BASIC program].
Gosub BBCF to do the following:
  Set BASIC PROGRAM START (MSB byte) page (&1D) to PAGE.
  Set BASIC Stack Pointer to HIMEM.
  Clear the top bit of &1F -> LISTO flag (to cancel *EDIT mode).
  Clear the Curent REPEAT level (&24).
  Clear the Current FOR level (&26).
  Clear the Current GOSUB level (&25).
  Clear the BASIC PROGRAM START LSB address (&1C).

Copy the 16-byte table in BASIC ROM locations &BF14 to &BF23 to page 7 (RAM) locations
&07F0 to &07FF. This is the Floating-Point routine table, and provides the address
for various routines which can be called from an assembly language program.

This table contains the following information (all addresses are stored LSB first):

This page 7 information will be overwritten if a BASIC text (program) line is entered
which exceeds &F0 characters. But BASIC refreshes this information often, so that
it will always be available to assembly language programs.

Zero the locations &0480 to &04FF. This will overwrite the BASIC variable pointer table.
This will, however, preserve the resident Integer (A%, B%, etc...) workspace and
the Temporary Floating-Point variable areas.

Disassembly for the Initialise Page 7, etc...