C庫函數 void isalnum(int c)檢查，傳遞的字符字母是否為數字。

聲明

以下是isalnum（）函數的聲明。

int isalnum(int c);

參數

• c -- 這是要檢查的字符。

返回值

這個函數返回非零值，如果c是一個數字或字母，否則為0

實例

下麵的例子顯示isalnum（）函數的用法。

#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);
}

讓我們編譯和運行上麵的程序，這將產生以下結果：

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