Category:XPL0

XPL0
This programming language may be used to instruct a computer to perform a task.

See Also:	XPL0 on the HOPL

Listed below are all of the tasks on Rosetta Code which have been solved using XPL0.

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 DOS. Free, open-source versions of the compilers (interpreted, assembly-code compiled, and optimizing) are available from the official website: xpl0.org [1]. The 32-bit version of the DOS compiler, XPLPX, was used for most of these Rosetta Code tasks, but more recent tasks were implemented using the compilers for the Raspberry Pi.

Here's how the traditional Hello World program is coded:

      code Text=12;
      Text(0, "Hello World!")

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 written as:

      Text(0, "Hello World!")