Category:XPL0: Difference between revisions
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'''XPL0''' is essentially a cross between Pascal and C. It was created in 1976
by Peter J. R. Boyle, who designed it to run on a 6502 microcomputer as
an alternative to BASIC, which was the dominant language for personal
computers at the time. XPL0 is based on PL/0, an example compiler in the
book ''Algorithms + Data Structures = Programs'' by Niklaus Wirth. The first
compiler was written in ALGOL. This was used to create a compiler
written in XPL0 syntax.
The language has been implemented on over a dozen processors, but is
currently maintained for IBM-type PCs. Free, open-source versions of the
compilers (interpreted, assembly code compiled, and optimizing) are
available from the official website: xpl0.org [http://www.xpl0.org/]
Here is how the traditional Hello World program is coded:
<pre>
code Text=12;
Text(0, "Hello World!")
</pre>
Text is a built-in routine, called an ''intrinsic'', that outputs a string
of characters. The zero (0) tells where to send the string. In this case
it is sent to the display screen; but it could just as easily be sent to
a printer, a file, or out a serial port by using a different number.
All names must be declared before they can be used. The command word
''code'' associates the name Text to the built-in routine number 12, which
outputs strings. There are about 80 of these built-in routines that
provide capabilities such as input and output, graphics, and trig
functions.
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