Question

What is the function to determine the min and max possible of value of datatypes (i.e, int, char.etc) in C?

Answer 1

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.