Parts, Numbers and Pixels: teacher key

How Computers Work, grade 8 edition, written for 8th grade. Meet a computer's parts, its memory and its program steps, then see how it turns pictures, colors and sound into numbers.

Read the book. Print this page for the key.

Questions and answers

1. Where is the origin (0, 0) on a pixel grid?
   • Upper left corner (answer)
   • Lower right corner
   • Center
2. What numbers can each of red, green and blue take in the RGB scheme?
   • 1 to 100
   • 0 to 255 (answer)
   • 0 to 8
3. How many pixels does an 800 by 600 image have?
   • 4,800
   • 1,400
   • 480,000 (answer)
4. What does a compiler do?
   • Translates source code into machine code (answer)
   • Squeezes sound
   • Etches silicon
5. A song is a real-world signal. How does a computer keep it?
   • As a list of numbers (answer)
   • As mixed paint
   • As a grid origin

Words

• pixels: tiny squares
• megapixels: million pixels
• compression: squeezing data
• compiler: code translator