What is the function to determine the min and max possible of value of datatypes (i.e, int, char.etc) in C?
What is the function to determine the min and max possible of value of datatypes (i.e, int, char.etc) in C?
You'll want to use limits.h which provides the following constants (as per the linked reference):
SCHAR_MIN : minimum value for a signed char
SCHAR_MAX : maximum value for a signed char
UCHAR_MAX : maximum value for an unsigned char
CHAR_MIN : minimum value for a char
CHAR_MAX : maximum value for a char
SHRT_MIN : minimum value for a short
SHRT_MAX : maximum value for a short
USHRT_MAX : maximum value for an unsigned short
INT_MIN : minimum value for an int
INT_MAX : maximum value for an int
UINT_MAX : maximum value for an unsigned int
LONG_MIN : minimum value for a long
LONG_MAX : maximum value for a long
ULONG_MAX : maximum value for an unsigned long
LLONG_MIN : minimum value for a long long
LLONG_MAX : maximum value for a long long
ULLONG_MAX : maximum value for an unsigned long long
PTRDIFF_MIN : minimum value of ptrdiff_t
PTRDIFF_MAX : maximum value of ptrdiff_t
SIZE_MAX : maximum value of size_t
SIG_ATOMIC_MIN : minimum value of sig_atomic_t
SIG_ATOMIC_MAX : maximum value of sig_atomic_t
WINT_MIN : minimum value of wint_t
WINT_MAX : maximum value of wint_t
WCHAR_MIN : minimum value of wchar_t
WCHAR_MAX : maximum value of wchar_t
CHAR_BIT : number of bits in a char
MB_LEN_MAX : maximum length of a multibyte character in bytes
Where U*_MIN is omitted for obvious reasons (any unsigned type has a minimum value of 0).
Similarly float.h provides limits for float and double types:
FLT_MIN : smallest normalised positive value of a float
FLT_MAX : largest positive finite value of a float
DBL_MIN : smallest normalised positive value of a double
DBL_MAX : largest positive finite value of a double
LDBL_MIN : smallest normalised positive value of a long double
LDBL_MAX : largest positive finite value of a long double
FLT_DIG : the number of decimal digits guaranteed to be preserved converting from text to float and back to text
DBL_DIG : the number of decimal digits guaranteed to be preserved converting from text to double and back to text
LDBL_DIG : the number of decimal digits guaranteed to be preserved converting from text to long double and back to text
Floating point types are symmetrical around zero, so the most negative finite number is the negation of the most positive finite number - eg float ranges from -FLT_MAX to FLT_MAX.
Do note that floating point types can only exactly represent a small, finite number of values within their range. As the absolute values stored get larger, the spacing between adjacent numbers that can be exactly represented also gets larger.
The header file limits.h defines macros that expand to various limits and parameters of the standard integer types.
Look at the these pages on limits.h and float.h, which are included as part of the standard c library.
To get the maximum value of an unsigned integer type t whose width is at least the one of unsigned int (otherwise one gets problems with integer promotions): ~(t) 0. If one wants to also support shorter types, one can add another cast: (t) ~(t) 0.
If the integer type t is signed, assuming that there are no padding bits, one can use:
((((t) 1 << (sizeof(t) * CHAR_BIT - 2)) - 1) * 2 + 1)
The advantage of this formula is that it is not based on some unsigned version of t (or a larger type), which may be unknown or unavailable (even uintmax_t may not be sufficient with non-standard extensions). Example with 6 bits (not possible in practice, just for readability):
010000 (t) 1 << (sizeof(t) * CHAR_BIT - 2)
001111 - 1
011110 * 2
011111 + 1
In two's complement, the minimum value is the opposite of the maximum value, minus 1 (in the other integer representations allowed by the ISO C standard, this is just the opposite of the maximum value).
Note: To detect signedness in order to decide which version to use: (t) -1 < 0 will work with any integer representation, giving 1 (true) for signed integer types and 0 (false) for unsigned integer types. Thus one can use:
(t) -1 < 0 ? ((((t) 1 << (sizeof(t) * CHAR_BIT - 2)) - 1) * 2 + 1) : (t) ~(t) 0