with 9K left spare, and while it can’t compare with a good 16K Basic,
it is a lot better than the arbitary standard ‘8K Basic’.
XTAL Basic uses the minimum number of calls to monitor
routines, and all these are made through a short table of jump
instructions. This means that these are easily changed to cope with any
monitor changes. The tape is issued with a NASBUG version recorded in
Nascom 1 format on one side, and a NAS-SYS version recorded in Nascom 2
format on the other. However the manual describes how to change one
version to the other, and this would only take a few minutes, and the
changed version stored on your own tape. One criticism here is that the
NAS-SYS version does not follow the NAS-SYS ‘rules’, and uses absolute
jumps instead of the NAS-SYS restart instructions. However, this is
easily corrected as shown in the tabulation of the jump table (below)
which starts at 2BDDH. The tabulation shows the correct values for
NAS-SYS, and ensures that upward compatibility is maintained.
Comparison of commands
XTAL Basic has the following extra commands:
EDIT This allows a program to be edited line by line. Characters can
be changed, inserted and deleted. Users of ‘SUPER TINY BASIC’
will notice a resemblance to the MCE comand. The XTAL Basic
does not support the convenient NAS-SYS editing, although this
method does have the advantage of allowing long lines (about
two lines on the screen). The cursor movement keys are not used
in the same ways as in NAS-SYS or Nascom Basic. Also CS is used
instead of ESC.
CSAVE & CLOAD are similar to the Nascom Basic but allow names of up to
six characters. The CLOAD routine stops when the first error is
encountered, so your cassette recorder must work well if you
have long programs.
PRINT @ X,Y,"ABC" prints ABC at the X,Y coordinate. This is similar to
using the Nascom Basic SCREEN command, followed by a PRINT
POP Deletes the return of a GOSUB, so that an abnormal exit can
easily be made from a subroutine.
SPEED up. Sets the output speed to allow the Basic display to be slowed