Category:XPL0: Difference between revisions
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'''XPL0''' is essentially a cross between Pascal and C. It looks somewhat like Pascal but works more like C. It was originally created in 1976
by Peter J. R. Boyle, who designed it to run on a 6502 microprocessor 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
XPL0 compiler was written in ALGOL, which was then used to create a compiler
written in XPL0's syntax.
XPL0 has been implemented on more than a dozen processors, but it's
currently maintained on the Raspberry Pi and IBM-type PCs. Programs run under Linux, Windows, and MS-DOS. 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/]. The 32-bit version of the MS-DOS compiler, XPLPX, was used for many of these Rosetta Code tasks, but more recent tasks were implemented using the compilers for the Raspberry Pi. Some tasks were implemented using [[EXPL-32]].
Here's 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 over a hundred of these built-in routines that
provide capabilities such as input and output, graphics, and trig
functions.
The 32-bit versions of the compilers (as opposed to the older, 16-bit versions) automatically declare ''code'' declarations. Thus the above program can simply be rewritten as:
<pre>
Text(0, "Hello World!")
</pre>
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