//create the memory file
fstream memory;

memory.open("memory/memory.txt", ios::in);

//then write your own phrases and responses : 

//user's phrase
memory << "Hi" << endl;
//machine's response
memory << "hi" << endl;

//phrase
memory << "How are you?" << endl;
//response
memory << "I'm doin just fine, thanks. Yourself?" << endl;

//etc.