Character Sets: Storing Text as Numbers · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Letters are numbers in disguise

Computing · Computer Systems · ages 14-15
Name ______________________   Date ____________

  1. After a program decodes text, a font draws the character shapes.

    Circle one:   True   False

  2. What is a character set?

    • A font that draws decoded glyphs from stored text
    • An agreed table pairing characters with code points
    • A file format that stores only pictures and their colour values

  3. In ASCII, what range contains the character codes?

    • 0 through 127
    • 128 through 255
    • Only 8 and 16

  4. A file saved with one character encoding is decoded with another. What is likely?

    • The bytes may become unexpected characters.
    • The font will change the file's stored bytes and use more storage.
    • The screen will change the file's stored bytes into larger pixels.

  5. In a table where the capital letters run in order with consecutive codes, D is 68. What code does G get?

    • 70
    • 71
    • 78

  6. Why was ASCII not enough for a world text standard?

    • It covered only a limited set of characters.
    • It could store English letters, but not any numbers or punctuation.
    • It made every file contain a picture instead of written characters.

  7. A file that looked fine on one computer opens as odd symbols on another. What is the likely cause?

    • The file contains too many words for the screen to display at its chosen width
    • The font was set to a smaller size than before, so the text looked compressed
    • The program used decoding rules that did not match the saved encoding

  8. The same bits can be a letter in one file and a colour value in another. What decides the meaning?

    • The size of the font used to display the decoded bits on screen
    • The file format and decoding rules used to read it
    • The length of the file name shown on the screen and in its folder
LightMySky · lightmysky.comW1-mt_839VNNZlp2-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

Letters are numbers in disguise W1-mt_839VNNZlp2-s1

  1. True · The decoder interprets the stored bytes. The font supplies the visible glyphs.
  2. An agreed table pairing characters with code points · A character set is the shared table that assigns characters to code points or numbers.
  3. 0 through 127 · ASCII uses 128 code values, numbered from 0 through 127.
  4. The bytes may become unexpected characters. · Different decoding rules can assign different characters to the same stored bytes.
  5. 71 · Letters in a run sit side by side, so G is three above D: 68 plus 3 is 71.
  6. It covered only a limited set of characters. · ASCII has a limited set of codes, so it cannot cover all writing systems and symbols. Unicode provides a much larger character set.
  7. The program used decoding rules that did not match the saved encoding · A decoding mismatch can turn the stored bytes into unexpected characters. Font size does not change the byte meanings.
  8. The file format and decoding rules used to read it · Bits do not carry a fixed meaning by themselves. The file format and decoding rules tell the program how to interpret them.
Worksheet · LightMySky