Types

Conversions

Type qualifiers

const

const int *p; //can't modify what p points to
*p = 10; //error

int *const p; //can't modify "p"
p++; //error

volatile

• Volatile tells the compiler that a value might change behind its back and should be looked up every time. E.g: some kind of hardware timer.
• “The thing this points at might change at any time for reasons outside this program code.”

volatile int *p;

static

• In block scope: static with an initializer will only be initialized one time on program startup.

void counter(void){
    static int count = 1;

    printf("This has been called %d time(s)\n", count);

    count++;
}

int main(){
    counter(); // This has been called 1 time(s)
    counter(); // This has been called 2 time(s)
    counter(); // This has been called 3 time(s)
}

• In file scope: the static variable in this context isn’t visible outside of this particular source file.

extern