Scope

Scope

Scope decides where a variable can be seen. Variables are born, live, and die in scoped regions.

Local variables

Variables declared inside a function are local: only that function can see them.

void myFunction() {
    int x = 10;    // local to myFunction
}

Outside myFunction, x doesn't exist.

Block scope

Variables inside { } blocks (like an if) are only alive inside that block.

if (1) {
    int y = 5;   // only visible inside the braces
}
printf("%d", y); // error: y is gone

Global variables

Variables declared outside any function are global: every function can read and write them.

int shared = 0;   // global

void up() { shared++; }

Use globals sparingly

Globals are convenient but make code harder to track. Prefer passing values via parameters.

TL;DR

• Scope = where a name is visible.
• Local variables live inside their function.
• Block-scoped variables die at their closing brace.
• Globals are visible everywhere; use them sparingly.