nes-pascal

Program structure

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A program contains:

  1. the program keyword;
  2. a program name;
  3. a semicolon;
  4. an optional type section;
  5. an optional const section;
  6. an optional var section;
  7. zero or more procedure and function declarations;
  8. a block beginning with begin;
  9. a sequence of statements;
  10. the end keyword;
  11. a final period.

Example:

program Minimal;

const
    DefaultBackgroundColor: nes_color = $21;

var
    BackgroundColor: nes_color;
    FrameCounter: byte;
    RenderingEnabled: boolean;

procedure Initialize(Start: byte; Enabled: boolean);
begin
    FrameCounter := Start;
    RenderingEnabled := Enabled;
end;

begin
    BackgroundColor := DefaultBackgroundColor;
    Initialize($00, true);
    nes.set_background_color(BackgroundColor);
    nes.run;
end.

The declaration sections must appear in this order: type, const, then var, followed by any interleaved procedures and functions. The main block contains the top-level initialization sequence and may continue with frame-synchronized main-thread logic after nes.run.

The type section may declare nominal enumerations and fixed-layout records. Record fields may use any declared enum in the section; nested record fields remain unsupported.

Static nes.on_update(Procedure) and nes.on_vblank(Procedure) registrations, when present, belong to the unconditional top-level initialization sequence before nes.run. See Frame callbacks.

The optional nes.load_background() command is also an unconditional, top-level initialization statement before nes.run. It has no arguments and requires configured nametable data.

Bounded runtime background updates may be staged from main code or procedures. Their queue-mutating operations are not allowed on a VBlank callback path; the simple overflow query is safe there.

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