The standard environment (The GNU Algol 68 Compiler)

### 2.5 The standard environment ¶

The environment in which particular programs run is expressed here in the form of pseudo code:

    (c standard-prelude c;
     c library-prelude c;
     c system-prelude c;
     par begin c system-task-1 c,
               c system-task-2 c,
               c system-task-n c,
               c user-task-1 c,
               c user-task-2 c,
               c user-task-m c
         end)

Where each user task consists of:

    (c particular-prelude c;
     c user-prelude c;
     c particular-program c;
     c particular-postlude c)

The only standard system task described in the report is expressed in pseudo-code as:

    do down gremlins; undefined; up bfileprotect od

Which denotes that, once a book (file) is closed, anything may happen. Other system tasks may exist, depending on the operating system. In general these tasks in the parallel clause denote the fact that the operating system is running in parallel (intercalated) with the user’s particular programs.

- The library-prelude contains, among other things, the prelude parts of the defining modules provided by library.
- The particular-prelude and particular-postlude are common to all the particular programs.
- The user-prelude is where the prelude parts of the defining modules involved in the compilation get stuffed. If no defining module is involved then the user-prelude is empty.

Subsequent sections in this manual include a detailed description of the contents of these preludes.