NAME
zmakebas - convert text file into Spectrum Basic program
SYNOPSIS
zmakebas [-hlr] [-a startline] [-i incr] [-n speccy_filename] [-o
output_file] [-s line] [input_file]
DESCRIPTION
zmakebas converts a Spectrum Basic program written as a text file into
an actual speccy Basic file (as a .TAP file, or optionally a raw
headerless file). By default, input comes from stdin, and output goes
to ‘out.tap’.
Using zmakebas rather than (say) writing the Basic in an emulator means
you can write using a nicer editor, and can use tools which work on
text files, etc. Also, with the ‘-l’ option you can write without line
numbers, using labels in their place where necessary.
The program was originally intended to be used simply to make little
loader programs, so they wouldn’t have to be sourceless binaries.
However, I went to a fair amount of effort to make sure it’d work for
bigger, more serious programs too, so you can also use it for that kind
of thing.
OPTIONS
-a make the generated file auto-start from line startline. If ‘-l’
was specified, this can be a label, but don’t forget to include
the initial ‘@’ to point this out.
-h give help on command line options.
-i in labels mode, set line number increment (default 2).
-l use labels rather than line numbers.
-n specify filename to use in .TAP file (up to 10 chars), i.e. the
filename the speccy will see. Default is a blank filename (10
spaces).
-o output to output_file rather than the default ‘out.tap’. Use ‘-’
as the filename to output on stdout.
-r write a raw headerless Basic file, rather than the default .TAP
file.
-s in labels mode, set starting line number (default 10).
INPUT FORMAT
The input should be much as you would type into a speccy (a 128, to be
precise), with the following exceptions:
Lines starting with ‘#’ are ignored. This allows you to insert comments
which are not copied into the output Basic file.
Blank lines are ignored.
Case is ignored in keywords - ‘print’, ‘PRINT’, and ‘pRiNt’ are
equivalent.
You can optionally use ‘randomise’ as an alternative to ‘randomize’.
You can get hex numbers by using ‘bin’ with a C-style hex number, e.g.
to get 1234h you’d use ‘bin 0x1234’. (It appears in exactly that form
in the speccy listing, though, so don’t use it if you want to be able
to edit the output program on a speccy.)
You can get a pound sign (character 96 on a speccy) by using a
backquote (‘).
One input line normally equals one line of Basic, but you can use
backslash as the last character of a line to continue the statement(s)
on the next input line.
Rather than literally inserting block graphics characters and UDGs as
you would on a speccy, you should use an escape sequence. These begin
with a backslash (‘\’). To get a UDG, follow this backslash with the
UDG’s letter, in the range ‘a’ to ‘u’ (‘t’ and ‘u’ will only have the
desired effect if the program is run on a 48k speccy or in 48k mode,
though); both upper and lowercase work. To get the copyright symbol,
follow it with ‘*’. To get a block graphics character, follow it with a
two-character ‘drawing’ of it using spaces, dots, apostrophes and/or
colons. (For example, you’d get character 135 with ‘\’:’, and character
142 with ‘\:.’.) To get a literal ‘@’, follow it with ‘@’. (This is
needed only if the ‘-l’ option was given, but works whether it was or
not.) To specify a literal eight-bit character code to dump into the
Basic output file directly (to use for embedded colour control codes
and the like), use braces and a C-syntax number e.g. ‘\{42}’ for
decimal, and ‘\{0x42}’ for hex. Finally, as usual with such things, you
can get a literal backslash by following the first backslash with
another.
If the ‘-l’ option was given, line numbers must be omitted. Instead
these are automatically generated in the output, and you can use labels
where necessary as substitute line numbers for ‘goto’ commands etc. A
label is defined with the text ‘@label:’ at the beginning of a line
(possibly preceded by whitespace). It can be referred to (before or
after) with ‘@label’. Any printable ASCII character other than colon
and space can be used in a label name. Here’s an example of how labels
work, showing both the input and (listing of) the output - first, the
input:
goto @foo
print "not seen"
@foo: print "hello world"
Now the output:
10 GO TO 14
12 PRINT "not seen"
14 PRINT "hello world"
Note that case is significant for labels; ‘foo’ and ‘FOO’ are
different.
BUGS
There’s almost no syntax checking. To do this would require a complete
parser, which would be overkill I think. What’s wrong with ‘‘C Nonsense
in BASIC’’ as a syntax check, anyway? :-)
Excess spaces are removed everywhere other than in strings and rem
statements. I think this is generally what you’d want, but it could be
seen as a bad thing I s’pose.
Labels are substituted even in string literals. That’s arguably a
feature not a bug - the problem is, the label name has to be followed
by whitespace or a colon or EOL when referenced, which is fine for more
normal references but is less than ideal for references in strings.
In the label-using mode, two passes are made over the input, which
usually means the input must be from a file. If you like making one-
liner Basic programs with ‘echo’ and the like, I’m afraid you’ll have
to use line numbers. :-)
The inline floating-point numbers which have to be generated are not
always exactly the same as the speccy would generate - but they usually
are, and even when they’re not the difference is extremely small and
due to rounding error on the speccy’s part. For example, 0.5 is encoded
by the speccy as 7F 7F FF FF FF (exponent -1, mantissa approx.
0.9999999997672) and by zmakebas as 80 00 00 00 00 (exponent 0,
mantissa 0.5).
zmakebas has most of the same (parsing) problems, relative to the
original basic editor, that the 128 editor has. Specifically, you can’t
use variable names which clash with reserved words, so e.g. ‘ink ink’
doesn’t work; and certain tightly-packed constructions you might expect
to work, like ‘chr$a’, don’t (you need a space or bracket after CHR$).
These can be more of a problem with zmakebas though, due to the lack of
syntax checking.
The way tokenisation is done is sub-optimal, to say the least. If you
ran this code on a Z80, even the 128 editor’s tokenisation would seem
quick in comparison. (Here’s a hint of the full horror of it - program
lines take exponentially longer to tokenise the longer they are.)
However, since I never had a conversion take more than about a second
on my old 486 (it took a second for a 10k program), it hardly seems
worth the effort of fixing.
zmakebas has no problem with translating BIN numbers of more than 16
bits, unlike the speccy, though numbers with more than 32 significant
bits can only be approximated, and on machines where ‘unsigned long’ is
no more than 32 bits they’ll be very approximate. :-) (If this sounds
confusing, you should note that BIN numbers are translated when
entered, and only the 5-byte inline form is dealt with at runtime. This
also explains why the speccy tolerates the ‘bin 0x...’ construction.)
On machines without FP hardware, zmakebas will be rather slow (this is
due to the need to generate inline FP numbers).
Since Basic is an acronym, pedants will doubtless insist I should write
it as ‘BASIC’. But we live in a world with ‘laser’ etc., and at least I
can be bothered to capitalise the thing, right? :-)
SEE ALSO
fuse(1), xz80(1), xzx(1)
AUTHOR
Russell Marks (russell.marks@ntlworld.com).