#include <iostream>
#include <string>
#include <cctype>
using namespace std;

void upper(string & str);
void lower(string & str);
int main(int argc, char** argv) {
	//1.
	string a1 = "aBcd";
	//轉大寫 
	upper(a1);
	cout<<"a1 = "<<a1<<endl;
	
	//轉小寫 
	lower(a1);
	cout<<"a1 = "<<a1<<endl;
	
	return 0;
}

////轉大寫////////////////
void upper(string & str) 
{
	for(int i=0;i<str.size();i++)
	{
		str[i] = toupper(str[i]);
	}
}

////轉小寫////////////////
void lower(string & str) 
{
	for(int i=0;i<str.size();i++)
	{
		str[i] = tolower(str[i]);
	}
}