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 for IBM-type PCs. Programs run under DOS and under versions of Windows that can still run DOS apps. Free, open-source versions of the compilers (interpreted, assembly-code compiled, and optimizing) are available from the official website: xpl0.org (archived copy). The 32-bit version of the compiler, XPLPX, was used for all these Rosetta Code tasks.

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 about 80 of these built-in routines that provide capabilities such as input and output, graphics, and trig functions.

Tasks