Lab 4 context: why pointing devices matter

The mouse made direct manipulation practical. Windows, menus, drawing tools, games, graphical editors, and desktop file managers depend on continuous pointing input.

At the controller level, a mouse is a stream of packets. The format is small but contains ideas that recur in protocols: synchronization bits, signed movement, button state, overflow flags, and enable/disable commands. Unlike a keyboard scancode, a mouse packet describes movement. The program decides how relative deltas affect a cursor, camera, selection box, or game object.

From keyboard to mouse

The mouse uses the same i8042-style controller, but its data model is richer. A keyboard event can be one or two bytes. A mouse event is a packet whose bytes are meaningful only as a group.

Lab 4 bridges input and graphics. You do not need a full pointer UI yet, but the parser should be good enough for a final project. Keep the packet decoder independent from screen coordinates so applications can choose their own coordinate system, sensitivity, and clipping.