LanguageUpdated 2026-07-24

GPC variables and arrays

Understand signed 16-bit runtime values, global storage, local scope, initialization, and safe array indexing.

Overview

Standard GPC variables are signed 16-bit integers. That range affects arithmetic, counters, controller values, and intermediate results.

Arrays group indexed values. Keep indexes within declared bounds and be deliberate about global versus function-local lifetime.

GPC variables are signed 16-bit integers.
Global declarations appear before runtime blocks.
An array index must remain within the declared element range.
Overflow-sensitive arithmetic should be redesigned or checked against current compiler behavior.

Examples are intentionally small. Replace identifiers only with values documented for your target.

State and lookup valuesexample.gpc

int enabled = FALSE;
int levels[3] = { 25, 50, 75 };

main {
    if (enabled) {
        set_val(XB1_A, levels[1]);
    }
}

Names below are catalog entries, not guessed signatures. Open the official sources for current parameter and return-value details.

NameKindPurpose

intdeclaration

Declares signed 16-bit runtime variable storage.

int[]declaration

Declares indexed signed-integer storage.

Assuming standard variables are 32-bit.

Using a negative or out-of-range array index.

Relying on an uninitialized value instead of assigning intentionally.

Use these first-party references to confirm exact syntax and runtime behavior for your installed firmware and Studio version.