Signed integers can be of these types (the `int`

after `short`

, or `long`

is optional):

```
signed char c = 127; /* required to be 1 byte, see remarks for further information. */
signed short int si = 32767; /* required to be at least 16 bits. */
signed int i = 32767; /* required to be at least 16 bits */
signed long int li = 2147483647; /* required to be at least 32 bits. */
```

```
signed long long int li = 2147483647; /* required to be at least 64 bits */
```

Each of these signed integer types has an unsigned version.

```
unsigned int i = 65535;
unsigned short = 2767;
unsigned char = 255;
```

For all types but `char`

the `signed`

version is assumed if the `signed`

or `unsigned`

part is omitted. The type `char`

constitutes a third character type, different from `signed char`

and `unsigned char`

and the signedness (or not) depends on the platform.

Different types of integer constants (called *literals* in C jargon) can be written in different bases, and different width, based on their prefix or suffix.

```
/* the following variables are initialized to the same value: */
int d = 42; /* decimal constant (base10) */
int o = 052; /* octal constant (base8) */
int x = 0xaf; /* hexadecimal constants (base16) */
int X = 0XAf; /* (letters 'a' through 'f' (case insensitive) represent 10 through 15) */
```

Decimal constants are always `signed`

. Hexadecimal constants start with `0x`

or `0X`

and octal constants start just with a `0`

. The latter two are `signed`

or `unsigned`

depending on whether the value fits into the signed type or not.

```
/* suffixes to describe width and signedness : */
long int i = 0x32; /* no suffix represent int, or long int */
unsigned int ui = 65535u; /* u or U represent unsigned int, or long int */
long int li = 65536l; /* l or L represent long int */
```

Without a suffix the constant has the first type that fits its value, that is a decimal constant that is larger than `INT_MAX`

is of type `long`

if possible, or `long long`

otherwise.

The header file `<limits.h>`

describes the limits of integers as follows. Their implementation-defined values shall be equal or greater in magnitude (absolute value) to those shown below, with the same sign.

Macro | Type | Value —— | —— | —— `CHAR_BIT`

| smallest object that is not a bit-field (byte) | 8 `SCHAR_MIN`

| `signed char`

| -127 / -(27 - 1) `SCHAR_MAX`

| `signed char`

| +127 / 27 - 1 `UCHAR_MAX`

| `unsigned char`

| 255 / 28 - 1 `CHAR_MIN`

| `char`

| see below `CHAR_MAX`

| `char`

| see below `SHRT_MIN`

| `short int`

| -32767 / -(215 - 1) `SHRT_MAX`

| `short int`

| +32767 / 215 - 1 `USHRT_MAX`

| `unsigned short int`

| 65535 / 216 - 1 `INT_MIN`

| `int`

| -32767 / -(215 - 1) `INT_MAX`

| `int`

| +32767 / 215 - 1 `UINT_MAX`

| `unsigned int`

| 65535 / 216 - 1 `LONG_MIN`

| `long int`

| -2147483647 / -(231 - 1) `LONG_MAX`

| `long int`

| +2147483647 / 231 - 1 `ULONG_MAX`

| `unsigned long int`

| 4294967295 / 232 - 1

Macro | Type | Value —— | —— | —— `LLONG_MIN`

| `long long int`

| -9223372036854775807 / -(263 - 1) `LLONG_MAX`

| `long long int`

| +9223372036854775807 / 263 - 1 `ULLONG_MAX`

| `unsigned long long int`

| 18446744073709551615 / 264 - 1

If the value of an object of type `char`

sign-extends when used in an expression, the value of `CHAR_MIN`

shall be the same as that of `SCHAR_MIN`

and the value of `CHAR_MAX`

shall be the same as that of `SCHAR_MAX`

. If the value of an object of type `char`

does not sign-extend when used in an expression, the value of `CHAR_MIN`

shall be 0 and the value of `CHAR_MAX`

shall be the same as that of `UCHAR_MAX`

.

The C99 standard added a new header, `<stdint.h>`

, which contains definitions for fixed width integers. See the fixed width integer example for a more in-depth explanation.