c语言中判断数字字符

#include <stdio.h>
int isNum(char c){
    if(c>='0' && c<='9'){
        return 1;
    }
    return 0;
}
int main(){
    char ch;
    scanf("%c",&ch);
    if(isNum(ch)){
        printf("yes");
    }else{
        printf("no");
    }
    return 0;
}

#include <stdio.h>
int fun(char c)
{
    if(c>='0' && c<='9')
        return 1;
    return 0;
}
int main()
{
    char ch;
    scanf("%c",&ch);
    if(fun(ch) == 1)
        printf("yes");
    else
        printf("no");
    return 0;
}

供参考：

#include <stdio.h>
int isDigit(char c)
{
    if (c >= '0' && c <= '9')
        return 1;
    else
        return 0;
}
int main()
{
    char ch;
    scanf("%c",&ch);
    if (isDigit(ch))
        printf("Yes");
    else
        printf("No");
    return 0;
}