Compiler errors: no comprendo

This boot-up password program compiles and runs with MSVC++. Now I want to compile it using GCC (DJGPP), and I get this error which I don't understand:

password.cpp: In function 'int main(...)'
password.cpp: 48: implicit declaration of function 'int strcmpi(...)'

What? Implicit? Understood but not stated? Does anyone know what is meant by this error? I belive the same error applies to my every other call of 'strcmpi()', if I were to remove the one mentioned.

Here is the main function:

Code:

int main()
{
	char* password = new char[50];
	char* response = new char[50];
	bool ChangePassword = false;
	bool bypass = false;
	ifstream ReadPasswordFile;
	ofstream WritePasswordFile;
	ReadPasswordFile.open("c:\\password.psw");

	system("cls");

	if(ReadPasswordFile.fail())
	{
		cout << "Could not open password file: using default password" << endl;
		strcpy(password,"ishboo");
	}
	else
	{
		ReadPasswordFile.getline(password,50);
		if(password[0] == (char)141)
		{
			ReadPasswordFile.close();
			return 0;
		}
	}
	ReadPasswordFile.close();

	while(1)
	{
		cout << "What's the password?" << endl;
		//PASSWORD ENTRY PUMP (DISPLAYS ONLY '*')
		PasswordPump(response);
		//END PASSWORD ENTRY PUMP (DISPLAYS ONLY '*')
		if(!strcmpi(response,password))
		{
			cout << "Thanks youz!";
			for(int x = 12; x < strlen(response); x++)
				putch(32);//space
			putch('\n');
			if(ChangePassword)
			{
				while(1)
				{
					cout << "\nInput new password: ";
					PasswordPump(password);
					cout << endl;
					cout << "Plese retype: ";
					PasswordPump(response);
					cout << endl;
					if(!strcmpi(password,response))
					{
						WritePasswordFile.open("c:\\password.psw");
						if(!WritePasswordFile.fail())//if it succeeded
							WritePasswordFile << password;
						else
						{
							cout << "Could not open \"c:\\password.psw\"." << endl;
							break;
						}
						cout << "Password change complete!" << endl;
						WritePasswordFile.close();
						break;
					}
					else
					{
						cout << "Those two are inconsistant!" << endl;
					}
				}
			}
			if(bypass)
			{
				WritePasswordFile.open("c:\\password.psw");
				if(!WritePasswordFile.fail())//if it succeeded
					WritePasswordFile << (char)141;
				else
				{
					cout << "Could not open \"c:\\password.psw\"." << endl;
					break;
				}
				cout << "Password bypassed!" << endl;
				WritePasswordFile.close();
			}

			break;
		}
		else if(!strcmpi(response,"change password") || !strcmpi(response,"changepassword"))
		{
			ChangePassword = true;
			wrong(response);
		}
		else if(!strcmpi(response,"bypass"))
		{
			bypass = true;
			wrong(response);
		}
		else
			wrong(response);
	}

	//system("cls");
	return 0;
}

According to this article strcmpi is not supported by ansi c++. I bet if you use strcmp (without the 'i') your code will compile just fine.