INTRO - introduction to the programming language PASCAL.

References:

Pascal User Manual and Report
Kathleen Jensen and Niklaus Wirth
Springer-Verlag, New York, 1975 (2nd ed.).

Systematic Programming: An Introduction
Niklaus Wirth
Prentice-Hall, Englewood Cliffs, N. J. 1973.

Algorithms + Data Structures = Programs
Niklaus Wirth
Prentice-Hall, Englewood Cliffs, N. J. 1976.

Pascal is perhaps the favorite language of computer science education today. It has good control structures and powerful data structuring abilities, yet it is a simple language. These advantages make it popular for structured programming: it is easy to learn, programs written in it are easy to read, and a great deal of compile time checking is possible to ensure program correctness. Moreover, compilers for Pascal can be fast yet produce very efficient object code.

Pascal is recommended for teaching introductory programming, but it can also be used for general purpose programming. Some important features of Pascal are:

In addition to the numerical capabilities of Fortran or Algol-60, Pascal provides facilities for manipulating ASCII characters and new basic data types defined by symbolic constants.
The "set" data type provides a means of manipulating "bit maps" in a symbolic and readable way.
Subranges of symbolic constants and integers can be declared to enable range checking of values assigned to variables of subrange type, e.g. subscripts.
Data items can be allocated dynamically from a storage pool and accessed through pointers to do list processing.
"Record", a data type somewhat like PL/1 or COBOL "structures", enables associating related entities of different type.
"Array" as usual enables associating related entities of the same type.
File I/O is included in the language definition.
Use of recursive procedures is very inexpensive.

These features make Pascal a practical alternative for numeric computing, business data processing, or even systems programming. (Several compilers have been written in Pascal.) It is available on a wide variety of machines.

The Pascal compiler for GCOS-8 provides the user with a powerful and versatile language. In addition to standard Pascal, several extensions are included.

Constant-valued expressions may be used wherever a constant is legal in standard Pascal, and are evaluated at compile time.
Files may be opened dynamically.
External procedures (including ones written in Fortran or B) may be defined and called.
Pascal procedures can be separately compiled, kept in, and called from (random) libraries.
Various non-standard procedures and functions provide access to many GCOS-8 features, such as calling other commands.
The "case" statement, which in Pascal provides the function of a Fortran "computed goto" in a much more readable manner, is augmented by an optional "else" clause to select default actions.

This compiler is an independent implementation of the language, not related to Pascal compilers on other machines.

System Requirements:

The GCOS-8 Pascal compiler runs on the Bull HN DPS-8 family of computers. The SS mode compiler runs under TSS or batch; the NS mode compiler runs under accommodation mode, but prepares programs to run in NS mode.

Normally the run-time input/output routines read or write either standard system format Media 6 ASCII sequential files or Pascal binary sequential files. They will also read BCD files (Media 0, 2 or 3), and comdecks.