What Are Integer Literal Type? And How They Are Stored?

Question

I have just started learning C and a question has bugged me for a while now. If I write

int i = -1;
unsigned int j = 2;
unsigned int k = -2;

<

Answer 1

In C99 and C11

If you want to specifies the type of your integer you can use an integer constant:

You can write integer with decimal, octal or hexa representation:

int decimal = 42; // nothing special
int octal = 052; // 0 in front of the number
int hexa = 0x2a; // 0x
int HEXA = 0X2A; // 0X

Decimal representation:

By default, the type of -1, 0, 1, etc. is int, long int or long long int. The compiler must peak the type that can handle your value:

int a = 1; // 1 is a int
long int b = 1125899906842624; // 1125899906842624 is a long int

That only work for signed value, if you want unsigned value you need to add u or U:

unsigned int a = 1u;
unsigned long int b = 1125899906842624u;

If you want long int or long long int but not int, you can use l or L:

long int a = 1125899906842624l;

You can combine u and l:

unsigned long int a = 1125899906842624ul;

Finally, if you want only long long int, you can use ll or LL:

unsigned long long int a = 1125899906842624ll;

And again you can combine with u.

unsigned long long int a = 1125899906842624ull;

Octal and Hexadecimal representation:

Without suffix, a integer will match with int, long int, long long int, unsigned int, unsigned long int and unsigned long long int.

int a = 0xFFFF;
long int b = -0xFFFFFFFFFFFFFF;
unsigned long long int c = 0xFFFFFFFFFFFFFFFF;

u doesn't differ from decimal representation. l or L and ll or LL add unsigned value type.

---

This is similar to string literals.