C语⾔中isalnum（）函数和isalpha（）函数的对⽐使⽤C语⾔isalnum()函数：判断字符是否为英⽂字母或数字
头⽂件：
#include <ctype.h>
isalnum() ⽤来判断⼀个字符是否为英⽂字母或数字，相当于 isalpha(c) || isdigit(c)，其原型为：
int isalnum(int c);
【参数】c 为需要检测的字符。
【返回值】若参数c 为字母或数字，若 c 为 0 ~ 9 a ~ z A ~ Z 则返回⾮ 0，否则返回 0。
注意，isalnum()为宏定义，⾮真正函数。
【实例】找出str 字符串中为英⽂字母或数字的字符。
#include <ctype.h>
main(){
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char str[] = "123c@#FDsP[e?";
int i;
热狗英语for (i = 0; str[i] != 0; i++)
if(isalnum(str[i]))
printf("%c is an alphanumeric character\n", str[i]);
}
小学生开学
输出结果：
1 is an apphabetic character
2 is an apphabetic character
3 is an apphabetic character
c is an apphabetic character
F is an apphabetic character
D is an apphabetic character
s is an apphabetic character
P is an apphabetic character
e is an apphabetic character
C语⾔isalpha()函数：判断字符是否为英⽂字母
头⽂件：
#include <ctype.h>
isalpha() ⽤来判断⼀个字符是否是英⽂字母，相当于 isupper(c)||islower(c)，其原型为：
五香果
int isalpha(int c);
【参数】c 为需要被检测的字符。
【返回值】若参数c 为英⽂字母（a ~ z A ~ Z），则返回⾮ 0 值，否则返回 0。
注意，isalpha() 为宏定义，⾮真正函数。
【实例】找出str 字符串中为英⽂字母的字符。
#include <ctype.h>
main(){
deorechar str[] = "123c@#FDsP[e?";
int i;
for (i = 0; str[i] != 0; i++)
if(isalpha(str[i]))
printf("%c is an alphanumeric character\n", str[i]);
}
杰克道森
执⾏结果：
c is an apphabetic character
日记40字>扇枕温衾的故事F is an apphabetic character
D is an apphabetic character
s is an apphabetic character
P is an apphabetic character e is an apphabetic character
