字符串中大写字母转化为小写字母

#include <stdio.h> 

main() 
{ 
   char a[100]; 
   int  i = 0; 
   printf( "输入字符串：\n" );
   gets( a );
   while( a[i] )
   {
       if( a[i] >= 'A' && a[i] <= 'Z' )
           a[i]  = a[i] + 32;
       i++;
   } 
   printf( "字符串中大写字母转化后结果：\n" );
   puts( a ); 
}