C库函数void isalpha(int c) 检查，传递的字符是否为字母。 

声明

以下是isalpha（）函数的声明。

int isalpha(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是一个字母，否则为0

实例

下面的例子显示isalpha（）函数的用法。

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

int main()
{
   int var1 = 'd';
   int var2 = '2';
   int var3 = '	';
   int var4 = ' ';
    
   if( isalpha(var1) )
   {
      printf("var1 = |%c| is an alphabet
", var1 );
   }
   else
   {
      printf("var1 = |%c| is not an alphabet
", var1 );
   }
   if( isalpha(var2) )
   {
      printf("var2 = |%c| is an alphabet
", var2 );
   }
   else
   {
      printf("var2 = |%c| is not an alphabet
", var2 );
   }
   if( isalpha(var3) )
   {
      printf("var3 = |%c| is an alphabet
", var3 );
   }
   else
   {
      printf("var3 = |%c| is not an alphabet
", var3 );
   }
   if( isalpha(var4) )
   {
      printf("var4 = |%c| is an alphabet
", var4 );
   }
   else
   {
      printf("var4 = |%c| is not an alphabet
", 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 an alphabet
var2 = |2| is not an alphabet
var3 = | | is not an alphabet
var4 = | | is not an alphabet