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 ); }