iissddiiggiitt() -- ctype Function (libc)

Check if a character is a numeral
#iinncclluuddee <ccttyyppee.hh>
iinntt iissddiiggiitt(_c) iinntt _c;

iissddiiggiitt() tests  whether the argument _c  is a numeral (00-99).   It returns a
number other than zero if _c is a numeral, and zero if it is not.  iissddiiggiitt()
assumes that _c is an ASCII character or EEOOFF.

_E_x_a_m_p_l_e
For an example of how to use this macro, see the entry for ccttyyppee.hh.

_S_e_e _A_l_s_o
AASSCCIIII, lliibbcc
ANSI Standard, section 7.3.1.4
POSIX Standard, section 8.1
