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      isdigit

      From cppreference.com
      <c‎ |string‎ |byte
       
       
       
       
      Defined in header<ctype.h>
      int isdigit(int ch);

      Checks if the given character is a numeric character (0123456789).

      The behavior is undefined if the value ofch is not representable asunsignedchar and is not equal toEOF.

      Contents

      [edit]Parameters

      ch - character to classify

      [edit]Return value

      Non-zero value if the character is a numeric character, zero otherwise.

      [edit]Notes

      isdigit andisxdigit are the only standard narrow character classification functions that are not affected by the currently installed C locale, although some implementations (e.g. Microsoft in1252 codepage) may classify additional single-byte characters as digits.

      [edit]Example

      Run this code
      #include <ctype.h>#include <limits.h>#include <stdio.h> int main(void){for(int ndx=0; ndx<=UCHAR_MAX;++ndx)if(isdigit(ndx))printf("%c", ndx);printf("\n");}

      Output:

      0123456789

      [edit]References

      • C23 standard (ISO/IEC 9899:2024):
      • 7.4.1.5 The isdigit function (p: TBD)
      • C17 standard (ISO/IEC 9899:2018):
      • 7.4.1.5 The isdigit function (p: 146)
      • C11 standard (ISO/IEC 9899:2011):
      • 7.4.1.5 The isdigit function (p: 201)
      • C99 standard (ISO/IEC 9899:1999):
      • 7.4.1.5 The isdigit function (p: 182)
      • C89/C90 standard (ISO/IEC 9899:1990):
      • 4.3.1.4 The isdigit function

      [edit]See also

      checks if a wide character is a digit
      (function)[edit]
      ASCII valuescharacters

      iscntrl
      iswcntrl

      isprint
      iswprint

      isspace
      iswspace

      isblank
      iswblank

      isgraph
      iswgraph

      ispunct
      iswpunct

      isalnum
      iswalnum

      isalpha
      iswalpha

      isupper
      iswupper

      islower
      iswlower

      isdigit
      iswdigit

      isxdigit
      iswxdigit

      decimal hexadecimal octal
      0–8\x0–\x8\0–\10control codes (NUL, etc.)≠000000000000
      9\x9\11tab (\t)≠00≠0≠000000000
      10–13\xA–\xD\12–\15whitespaces (\n,\v,\f,\r)≠00≠0000000000
      14–31\xE–\x1F\16–\37control codes≠000000000000
      32\x20\40space0≠0≠0≠000000000
      33–47\x21–\x2F\41–\57!"#$%&'()*+,-./0≠000≠0≠0000000
      48–57\x30–\x39\60–\7101234567890≠000≠00≠0000≠0≠0
      58–64\x3A–\x40\72–\100:;<=>?@0≠000≠0≠0000000
      65–70\x41–\x46\101–\106ABCDEF0≠000≠00≠0≠0≠000≠0
      71–90\x47–\x5A\107–\132GHIJKLMNOP
      QRSTUVWXYZ      		0≠000≠00≠0≠0≠0000
      91–96\x5B–\x60\133–\140[\]^_`0≠000≠0≠0000000
      97–102\x61–\x66\141–\146abcdef0≠000≠00≠0≠00≠00≠0
      103–122\x67–\x7A\147–\172ghijklmnop
      qrstuvwxyz      		0≠000≠00≠0≠00≠000
      123–126\x7B–\x7E\173–\176{|}~0≠000≠0≠0000000
      127\x7F\177backspace character (DEL)≠000000000000
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