To begin with, we look into the input of regular characters. The OnChar method is called every time a user presses a graphical character (with an ASCII value between 32 and 127, inclusive) or the Return key. If a part of the text is marked, that part is removed first. Then the character is added to the character list by the InsertChar method of the OverwriteChar class, depending on the keyboard mode.

void WordDocument::OnChar(TCHAR tChar) { 
  if (isprint(tChar) || (tChar == NewLine)) { 
    if (wordMode == WordMark) { 
      OnDelete(); 
    } 
 
    Paragraph* paragraphPtr = charList[editIndex].ParagraphPtr(); 
 
    switch (GetKeyboardMode()) { 
      case InsertKeyboard: 
        OnInsertChar(tChar, paragraphPtr); 
        break; 
 
      case OverwriteKeyboard: 
        OnOverwriteChar(tChar, paragraphPtr); 
        break; 
    } 
 
    SetDirty(true); 
    GenerateParagraph...