C语言中的isalnum()函数
该功能isalnum()用于检查字符是否为字母数字。它返回非零值，如果字符是字母数字，则表示字母或数字，否则返回零。在“ctype.h”头文件中声明。
这是isalnum()C语言的语法，
int isalnum(int character);
这里，
字符-要检查的字符。
这是isalnum()C语言的示例，
示例
#include<stdio.h>
#include<ctype.h>
int main() {
char val1 = 's';
char val2 = '8';
char val3 = '$';
if(isalnum(val1))
printf("The character is alphanumeric\n");
else
printf("The character is not alphanumeric\n");
if(isalnum(val2))
printf("The character is alphanumeric\n");
else
printf("The character is not alphanumeric");
if(isalnum(val3))
printf("The character is alphanumeric\n");
else
printf("The character is not alphanumeric");
return 0;
}输出结果
The character is alphanumeric The character is alphanumeric The character is not alphanumeric
在上面的程序中，声明了char类型的三个变量，并使用值对其进行了初始化。通过使用isalnum()函数检查这些变量是否是字母数字值。
if(isalnum(val1))
printf("The character is alphanumeric\n");
else
printf("The character is not alphanumeric\n");