C Standard Library -<limits.h>

Introduction

<limits.h>is a header file in the C standard library, defining limits for various data types. These macros provide information about integer types (char、short、int、longandlong longetc.) and the maximum and minimum values of other data types.

These limits specify that variables cannot store any values beyond these limits, for example, an unsigned can store a maximum value of 255.

Library macros

The following values are implementation-defined and are defined via the #define directive; these values must not be lower than the values given below.

Macro	Description	Value
Character types
`CHAR_BIT`	`char`Number of bits of the type	Usually 8
`CHAR_MIN`	`char`Minimum value of a type (signed or unsigned)	-128 or 0
`CHAR_MAX`	`char`Maximum value of a type (signed or unsigned)	127 or 255
`SCHAR_MIN`	`signed char`Minimum value of the type	-128
`SCHAR_MAX`	`signed char`Maximum value of the type	127
`UCHAR_MAX`	`unsigned char`Maximum value of the type	255
Short integer type
`SHRT_MIN`	`short`Minimum value of the type	-32768
`SHRT_MAX`	`short`Maximum value of the type	32767
`USHRT_MAX`	`unsigned short`Maximum value of the type	65535
Integer Types
`INT_MIN`	`int`Minimum value of the type	-2147483648
`INT_MAX`	`int`Maximum value of the type	2147483647
`UINT_MAX`	`unsigned int`Maximum value of the type	4294967295
Long integer type
`LONG_MIN`	`long`Minimum value of the type	-9223372036854775808L
`LONG_MAX`	`long`Maximum value of the type	9223372036854775807L
`ULONG_MAX`	`unsigned long`Maximum value of the type	18446744073709551615UL
Long long integer type
`LLONG_MIN`	`long long`Minimum value of the type	-9223372036854775808LL
`LLONG_MAX`	`long long`Maximum value of the type	9223372036854775807LL
`ULLONG_MAX`	`unsigned long long`Maximum value of the type	18446744073709551615ULL

Example

The following example demonstrates the use of some constants defined in the limit.h file.

Example

#include <stdio.h>
#include <limits.h>

int main() {
printf("Character types:\n");
printf("CHAR_BIT: %d\n", CHAR_BIT);
printf("CHAR_MIN: %d\n", CHAR_MIN);
printf("CHAR_MAX: %d\n", CHAR_MAX);
printf("SCHAR_MIN: %d\n", SCHAR_MIN);
printf("SCHAR_MAX: %d\n", SCHAR_MAX);
printf("UCHAR_MAX: %u\n", UCHAR_MAX);

printf("\nShort integer types:\n");
printf("SHRT_MIN: %d\n", SHRT_MIN);
printf("SHRT_MAX: %d\n", SHRT_MAX);
printf("USHRT_MAX: %u\n", USHRT_MAX);

printf("\nInteger types:\n");
printf("INT_MIN: %d\n", INT_MIN);
printf("INT_MAX: %d\n", INT_MAX);
printf("UINT_MAX: %u\n", UINT_MAX);

printf("\nLong integer types:\n");
printf("LONG_MIN: %ld\n", LONG_MIN);
printf("LONG_MAX: %ld\n", LONG_MAX);
printf("ULONG_MAX: %lu\n", ULONG_MAX);

printf("\nLong long integer types:\n");
printf("LLONG_MIN: %lld\n", LLONG_MIN);
printf("LLONG_MAX: %lld\n", LLONG_MAX);
printf("ULLONG_MAX: %llu\n", ULLONG_MAX);

return 0;
}

Let us compile and run the above program, which will produce the following results:

Character types:
CHAR_BIT: 8
CHAR_MIN: -128
CHAR_MAX: 127
SCHAR_MIN: -128
SCHAR_MAX: 127
UCHAR_MAX: 255

Short integer types:
SHRT_MIN: -32768
SHRT_MAX: 32767
USHRT_MAX: 65535

Integer types:
INT_MIN: -2147483648
INT_MAX: 2147483647
UINT_MAX: 4294967295

Long integer types:
LONG_MIN: -9223372036854775808
LONG_MAX: 9223372036854775807
ULONG_MAX: 18446744073709551615

Long long integer types:
LLONG_MIN: -9223372036854775808
LLONG_MAX: 9223372036854775807
ULLONG_MAX: 18446744073709551615

<limits.h>It provides many macros related to integer types, used to describe the limits of various data types. These macros are very useful for writing robust and portable code, because they allow programmers to easily obtain the limit values of data types on different platforms.

other extensions