Edexcel 1CP2 2.1.2: Unsigned and two's complement integers
The free BugBot lesson that teach this point, a robot to try it on, and the past-paper questions that test it.
What it covers
So far every binary number has been positive. But a robot needs negatives too: a turn to the left, a speed in reverse, a temperature below zero. Two's complement is how nearly every computer stores negative whole numbers, and it has a lovely property: the same adding circuit works for positives and negatives alike.
- The idea
- Making a number negative
- Why it works so well
- Negative speeds
Or do it in the simulator, with tasks that mark themselves
Lessons that teach it
- F8.5 Negative numbers: two's complement Data representation
Signed 8-bit integers, and why the same adder works for them.
Try it on a robot
The task from F8.5 Negative numbers: two's complement, running here. Change the program and press Run.
The specification is Edexcel's own document; this page says which of our lessons teach point 2.1.2 and is not endorsed by the board.