Functions & Prototypes in C

From the C cheat sheet · Functions · verified Jul 2026

Definitions, prototypes, and recursion.

// Quick Reference
int add(int a, int b);      // prototype (declaration)

int add(int a, int b) {     // definition
    return a + b;
}

💡 Declare a prototype (or include its header) before you call a function.

⚡ C passes arguments by value - pass a pointer (int *p) to modify the caller's variable.

📌 static on a function limits it to the current file; on a local var it persists across calls.

🟢 Mark pointer params const (const char *) when the function only reads through them.

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