Introduction

Welcome to XPL0!

XPL0 bridges the gap between assembly language and high-level language. It has the speed and flexibility of assembly language, yet is easy to use. It's a block-structured language that can do floating-point calculations such as trig functions.

Programs that have been written in XPL0 include: compilers, operating systems, word processors, video games, and medical instrument controllers. These programs might have been written in assembly language, but because they were written in XPL0 they were written quickly, and they can be easily modified.

If XPL0 is your first high-level language, or if you are familiar with other block-structured languages such as C or Pascal, you will find XPL0 logical and easy to learn. If your programming experience is with a non- structured language such as BASIC, a structured language might seem awkward at first. This is because it requires more setup. However, as your programs grow and your skill increases, you'll begin to appreciate the power of a block-structured language.

XPL0 was created in the mid seventies by P.J.R. Boyle and the 6502 Group, a computer club at the Colorado School of Mines in Golden. Since then, there have been many versions of XPL0 running on many different computers (6502, PDP-10, IBM-360, homebrews, 8080, 6800, 65802, 680x0 and 80x86). This manual describes the (16-bit) versions that run on IBM-style PCs.

This manual is both a tutorial and a reference. The information is in a logical order for reference, but in some cases this makes it more difficult when first learning the language. It is best to skip the sections marked "Advanced" when reading the manual the first time.

To help you get started, here is more detailed information about writing programs, compiling programs and XPL syntax: