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Intro to CS 9-10 / Week 09 / Mission Quest
6/6
Week 09 · Bits and Binary

Mission Quest

Mission Quest: Five-card binary
// Place values, one byte, overflow, and sampling a smooth curve
⏱ about 20 min

Mission Quest: Five-Card Binary

The greenhouse lights dim for the evening, and the crew sits down with a handful of paper cards.

Comet holds up five cards marked 16, 8, 4, 2 and 1. Three face up, two face down.

"Quick," she says. "What number?"

Wren scans the cards. "Sixteen, four and one. Twenty-one."

Nova blinks twenty-one tiny lights in a ring, then turns them off one by one. "Correct," she says. "Great discovery!"

Wren gathers the cards. "My turn to show one. No peeking, Comet."

  1. A bit is 0 or 1, and a byte is 8 bits.
  2. Binary place values from the right are 1, 2, 4, 8, 16, 32, 64 and 128.
  3. One byte holds whole numbers from 0 to 255. Going past 255 causes an overflow error.
  4. The same bits can mean a number, a letter or a color, depending on the context.
  5. Sampling stores smooth analog data as digital samples, an approximation.
◇ FIVE-CARD BINARY
Make five cards marked 16, 8, 4, 2 and 1. Lay them in a row with 16 on the left.
One player secretly picks a number from 0 to 31 and shows it with the cards.
Face up means 1. Face down means 0.
The others race to decode it. The first right answer shows the next number.
Round two: decoders say the number in binary out loud, like "one zero one zero one."
Round three: use the crew letter code. Show a short word, one letter at a time.
For a grown-up
Ask: how can only two symbols, 0 and 1, stand for any number?
Ask: who in our community might not have easy access to a computer or the Internet? What could help?
This course is unplugged. Your student never needs an app, an account or a website.
QUEST CHECK
  • Read the question.
  • Tap your answer.
With five cards, what is the largest number you can show?
Cards 16, 4 and 1 are face up. What is the five-bit pattern?
Which cards show 19?
Bit is short for binary what? Type one word.
WHY THIS EXERCISEEvery value a computer stores is built from binary digits.
On paper, draw the five cards showing the largest number you decoded tonight, and write its value.
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