char - How can you assign a character value to a integer type variable in C?

Question

In C,

...
int num = 'a';
...

My question is simple. How can you assign a character such as '0', 'a', 'b' to an integer type variable without getting any type error in C language?

Answer 1

For historical reasons (mostly), character constants are of type int in C.

But even if they weren't, an initialization like

int num = 'a';

or an assignment like

num = 'a';

would still be perfectly legal. A value of any numeric type may be assigned to a variable of any (other) numeric type, and the value will be implicitly converted (which may involve a change of representation and/or a risk of overflow).

And char, along with its relatives unsigned char and signed char, are numeric types, specifically integer types.