在C語言中，可以使用isdigit()、isalpha()、isalnum()等標準庫函數來判斷字符的類型。
這些函數的使用方法如下所示：
#include <stdio.h>
#include <ctype.h>
int main() {
char ch = 'A';
if (isdigit(ch)) {
printf("The character is a digit.\n");
} else {
printf("The character is not a digit.\n");
}
if (isalpha(ch)) {
printf("The character is an alphabet.\n");
} else {
printf("The character is not an alphabet.\n");
}
if (isalnum(ch)) {
printf("The character is an alphabet or digit.\n");
} else {
printf("The character is neither an alphabet nor a digit.\n");
}
return 0;
}
