Ready-to-use computing activity
Binary Byte Detective
Teacher overview
Prior knowledge: Learners should know that binary uses 0 and 1 and that each bit position has a place value.
Learning objective: Convert between 8-bit binary, decimal and simple hexadecimal while using evidence to decode a hidden message.
Starter
Show 01000001 and ask learners what changes when one bit is switched on or off.
Main task
- Complete the 8-bit place-value grid for 1, 2, 4, 8, 16, 32, 64 and 128.
- Convert 00001010, 00001111, 00100000, 01000001 and 01111111 into decimal.
- Convert 5, 12, 31, 64 and 100 into 8-bit binary.
- Use Binary Lab to test two answers, then explain any mistake found.
- Decode the message: 01001000 01001001. Each byte is an ASCII-style clue for a capital letter.
Support prompts
- Start from the right-hand bit.
- Add only the place values where the bit is 1.
- Use leading zeroes to keep every answer at 8 bits.
Challenge
Convert 1111 to hexadecimal, then explain why 11111111 is FF.
Plenary or exit question
Which single bit change creates the biggest decimal change, and why?