ZX Computings - OpenLibra

A. Beasley
After using the ZX80 for a
few months I found that there
was a need for a simple
renumbering program. In the
attempt to solve the problem a
BASIC program was written
out but this took far too much
memory space. While machine
code was the obvious solution
it did raise yet another
problem. How could the
program be stored so that it
could be used without any
trouble. After attempting to
store it in a REM line it was
found that some of the codes
made the system crash when
the program was listed.
Solutions
To get over the problem the
following method was
developed. First all the
variables are CLE A Red. A
string variable is now set up to
contain the required number of
bytes and the machine code is
POKEd into it. As this string
variable is the first in the list
its location can be found from
the two bytes called VARS,
see page 1 22 in the manual.
By adding one to the value
obtained you have the location
of the first character in the
string. To call the program you
simply find the value of VARS,
add one and use this number
as a USR call.
More Problems
This method generates its own
set of problems, however. If
you are using it tor program
operation you cannot use the
following commands, RUN,
CLEAR or NEW. By using
GOTO you can get over the
RUN problem and the others
are not really drastic.
The main advantage of this
method is that when you save
the program you still preserve
the string for the next time. It
should be noted that the
GOTO and GOSUB statements
are not altered but you do get
everything into 35 bytes.
4ER 1982 ZX COMPUTING SUMMER 1982
Operation
To use the program type in
with Z$ containing 33
characters. Now run the
program then remove it by
typing just the line numbers
and then 'Newline'. The
program you wish to renumber
can be keyed in but remember
not to use the RUN or CLEAR
keys and make sure that the
program does not contain Z $.
To activate the renumber
type PRINT USR
(1 + PEEK(1 6392) + PEEK-
(1 6393)* 256).
1
2
3
4
5
6
7
8
9
10
1 1
12
13
CLEAR
LET Z$ • *aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
LET
A$ = '06000E0A2128407023713E0A814F30-
0404 CB70C0237EFE7620FA237ECB7FC018E6"
LET A = 1 + PEEK! 16392) + PEEK! 1 6393*256)
FOR C = 1 TO 33
LET B = CODE (A$)-28
LET B = B* 16
LET A$ -TL$(A$)
LET B = B + C0DE(A$) - 28
LET A$ =TL${A$}
POKE A,B
LET A = A + 1
NEXT C