IT. Expert System.

The ctype.h header file of the C Standard Library provides declares several functions useful for testing and mapping characters. All the functions accepts int as a parameter, whose value must be EOF or representable as an unsigned char. All the functions return non-zero (true) if the argument c satisfies the condition described, and zero if not

Syntax:

#include

Example:

#include 
#include 
#include 
#include 

void main() {
 int test;
 char *ans[2] = {" not ", ""};

 for (test = -1; test < 256; test++)
 {
    printf("\n\n\nthe value %02x is:\n",
       test);
    printf("%salphanumeric\n",
       ans[(isalnum(test) != 0)]);
    printf("%sa letter\n",
       ans[(isalpha(test) != 0)]);
    printf("%sascii\n",
       ans[(__isascii(test) != 0)]);
    printf("%sa control\n",
       ans[(iscntrl(test) != 0)]);
    printf("%sa letter,
       underscore or digit\n",
       ans[(__iscsym(test) != 0)]);
    printf("%sa letter or underscore\n",
       ans[(__iscsymf(test) != 0)]);
    printf("%sa digit\n",
       ans[(isdigit(test) != 0)]);
    printf("%sprintable/ not a space\n",
       ans[(isgraph(test) != 0)]);
    printf("%slower case\n",
       ans[(islower(test) != 0)]);
    printf("%sprintable\n",
       ans[(isprint(test) != 0)]);
    printf("%sa punctuator\n",
       ans[(ispunct(test) != 0)]);
    printf("%swhite space\n",
       ans[(isspace(test) != 0)]);
    printf("%supper case\n",
       ans[(isupper(test) != 0)]);
    printf("%sa hexadecimal digit\n",
       ans[(isxdigit(test) != 0)]);
    printf("\n* press a key for the next
       value*\n"); getch();
 }
}

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