http://tw.knowledge.yahoo.com/question/question?qid=1610043006278

gistfile1.cpp

#include <iostream>
#define LENGTHCASE 26
#define CHARLOWERCASE 'a'
#define CHARUPPERCASE 'A'
// Integrated Development Environment
// Visual C++
using namespace std;
//
class CCase
{
public:
	CCase(void);
	void ToLowerCase(char* _cstring);
	void ToUpperCase(char* _cstring);
private:
	char m_lowercase[LENGTHCASE + 1];
	char m_uppercase[LENGTHCASE + 1];
};
void main(int argc, char** argv)
{
	CCase cc;
	char CStr_upper[] = "This is a BOOK.";
	char CStr_lower[] = "operating system";
	// 轉成小寫
	cc.ToLowerCase(CStr_upper);
	// 轉成大寫
	cc.ToUpperCase(CStr_lower);
	// 顯示字串
	cout<<CStr_upper<<endl;
	cout<<CStr_lower<<endl;
	system("PAUSE");
}
CCase::CCase(void)
{
	// 讓電腦自行建表
	for (size_t i = 0; i < LENGTHCASE; i ++)
	{
		this->m_lowercase[i] = CHARLOWERCASE + i;
		this->m_uppercase[i] = CHARUPPERCASE + i;
	}
	// 給個結束字元
	// 不一定要給，這只是用來除錯的
	this->m_lowercase[LENGTHCASE] = NULL;
	this->m_uppercase[LENGTHCASE] = NULL;
}
void CCase::ToLowerCase(char* _cstring)
{
	for (size_t i = 0; _cstring[i] != NULL; i ++)
	{
		for (size_t j = 0; j < LENGTHCASE; j ++)
		{
			// 只要有字元符合大寫，一律設定為小寫
			if ( _cstring[i] == this->m_uppercase[j] )
			{
				_cstring[i] = this->m_lowercase[j];
			}
		}
	}
}
void CCase::ToUpperCase(char* _cstring)
{
	for (size_t i = 0; _cstring[i] != NULL; i ++)
	{
		for (size_t j = 0; j < LENGTHCASE; j ++)
		{
			// 只要有字元符合小寫，一律設定為大寫
			if ( _cstring[i] == this->m_lowercase[j] )
			{
				_cstring[i] = this->m_uppercase[j];
			}
		}
	}
}