Two's Complement
How a computer stores negative integers: step-by-step conversion, a number circle of 4-bit patterns, addition with overflow, and practice with checking.
Free, runs in the browser, no sign-in or installation.
- Subject
- Computer Science
- Area
- Data Representation
- Level
- Secondary school
What you can do
- Type an integer, choose 4, 8 or 16 bits and follow the steps: write the absolute value in binary, invert every bit and add 1.
- Click a bit to change it and check the value of the pattern with place values, where the highest bit has a negative weight.
- A table and a number circle show all 16 four-bit patterns with their unsigned and two's complement values.
- Add two numbers as bit patterns with carries; the app marks the discarded carry and warns about overflow.
- Practise converting numbers to two's complement and back, with answer checking, a worked method and a count of correct answers.
Worksheets and lessons
Lessons with worksheets that use this app.