ไลบรารี ctype

#include <stdio.h>
#include <ctype.h>

int main(void) {
    printf("Is 'A' alpha? %d\n", isalpha('A'));
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    printf("isdigit('7') = %d\n", isdigit('7'));
    printf("isdigit('x') = %d\n", isdigit('x'));
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    printf("isalpha('G') = %d\n", isalpha('G'));
    printf("isalpha('3') = %d\n", isalpha('3'));
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    printf("isalnum('9') = %d\n", isalnum('9'));
    printf("isspace(' ') = %d\n", isspace(' '));
    printf("isspace('a') = %d\n", isspace('a'));
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    printf("isupper('A') = %d\n", isupper('A'));
    printf("islower('A') = %d\n", islower('A'));
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    printf("ispunct('!') = %d\n", ispunct('!'));
    printf("ispunct('a') = %d\n", ispunct('a'));
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    printf("%c\n", toupper('h'));
    printf("%c\n", toupper('5'));
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    printf("%c\n", tolower('H'));
    printf("%c\n", tolower('z'));
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    char *s = "abc123";
    int letters = 0, digits = 0;
    for (int i = 0; s[i]; i++) {
        if (isalpha(s[i])) letters++;
        if (isdigit(s[i])) digits++;
    }
    printf("letters=%d digits=%d\n", letters, digits);
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    char s[] = "Hello";
    for (int i = 0; s[i]; i++) {
        s[i] = toupper(s[i]);
    }
    printf("%s\n", s);
    return 0;
}

#include <stdio.h>
#include <ctype.h>

int main(void) {
    char c = 'Q';
    int result = isalpha((unsigned char)c);
    printf("safe isalpha = %d\n", result);
    return 0;
}