C库函数 void isalnum(int c)检查，传递的字符字母是否为数字。

声明

以下是isalnum（）函数的声明。

int isalnum(int c);

参数

• c -- 这是要检查的字符。

返回值

这个函数返回非零值，如果c是一个数字或字母，否则为0

实例

下面的例子显示isalnum（）函数的用法。

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

int main()
{
   int var1 = 'd';
   int var2 = '2';
   int var3 = '	';
   int var4 = ' ';
    
   if( isalnum(var1) )
   {
      printf("var1 = |%c| is alphanumeric
", var1 );
   }
   else
   {
      printf("var1 = |%c| is not alphanumeric
", var1 );
   }
   if( isalnum(var2) )
   {
      printf("var2 = |%c| is alphanumeric
", var2 );
   }
   else
   {
      printf("var2 = |%c| is not alphanumeric
", var2 );
   }
   if( isalnum(var3) )
   {
      printf("var3 = |%c| is alphanumeric
", var3 );
   }
   else
   {
      printf("var3 = |%c| is not alphanumeric
", var3 );
   }
   if( isalnum(var4) )
   {
      printf("var4 = |%c| is alphanumeric
", var4 );
   }
   else
   {
      printf("var4 = |%c| is not alphanumeric
", var4 );
   }
	
   return(0);
}

让我们编译和运行上面的程序，这将产生以下结果：

var1 = |d| is alphanumeric
var2 = |2| is alphanumeric
var3 = | | is not alphanumeric
var4 = | | is not alphanumeric

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