Unit 6 · Lesson 3
6 steps. Each one is a short story and a question to answer.
When you type the letter A, the computer doesn't see a "letter". It understands only numbers.
So every letter, digit or symbol is given a unique number called a character code.
For example the letter A has code 65, the digit 5 has its own code, and @ has its own.
A character code system is the table fixing each character's number, so the computer stores text as numbers.
Why do we need a code for each character?
Pick an answer
Character code = a unique number for each character, and the computer works with numbers. So every letter, digit or symbol is given a unique number called a character code. For example the letter A has code 65, the digit 5 has its own code, and @ has its own.
ASCII = numbers for English letters, digits and symbols, using one byte (256 possibilities). It gives a distinct number to each English letter, capital and small, the digits 0 to 9 and symbols like ! @ # $. It also has control characters that are not printed but control devices.
Letter, then decimal code, then 8 bits, then hex. First, find each letter's code in the ASCII table: H=72, e=101, l=108, o=111. Second, turn each number into 8-bit binary: for example H = 01001000.
Unicode = one unified number for every character of every language, stored as UTF-8 or UTF-16. Unicode is a global standard that gives every character in any language a unified number, instead of a different system per language. With 2 bytes (16 bits) it can represent 65,536 characters and symbols.
Encode, store, decode. If the system differs, characters get corrupted. Encoding converts text into character codes using a given system, like Hello to 72 101 108 108 111. Decoding is the reverse: turning the stored numbers back into text a person can read.
The code decides which letter; the font decides its look: serif, sans-serif, semi-cursive. The character code decides which letter it is (65 = A), while the font decides how it looks on screen or in print. Serif: fonts with small strokes at the ends, like Times New Roman. Sans-serif: no strokes and clearer, like Arial.
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Every idea in the lesson with its rule, ready to screenshot and revise from.
Character code = a unique number for each character, and the computer works with numbers
ASCII = numbers for English letters, digits and symbols, using one byte (256 possibilities)
Letter, then decimal code, then 8 bits, then hex
Unicode = one unified number for every character of every language, stored as UTF-8 or UTF-16
Encode, store, decode. If the system differs, characters get corrupted
The code decides which letter; the font decides its look: serif, sans-serif, semi-cursive
One question from every step. Answer and see your score.
Question 1 of 6
Why do we need a code for each character?
Unit 6
Learn how a computer understands letters: character codes, ASCII, Unicode, encoding and decoding, why text sometimes breaks, and font types, in an animated explainer.
The same explanation as the 3D scene, written out for quick review.
Character code = a unique number for each character, and the computer works with numbers. So every letter, digit or symbol is given a unique number called a character code. For example the letter A has code 65, the digit 5 has its own code, and @ has its own.
Page 104
ASCII = numbers for English letters, digits and symbols, using one byte (256 possibilities). It gives a distinct number to each English letter, capital and small, the digits 0 to 9 and symbols like ! @ # $. It also has control characters that are not printed but control devices.
Page 104, 105
Letter, then decimal code, then 8 bits, then hex. First, find each letter's code in the ASCII table: H=72, e=101, l=108, o=111. Second, turn each number into 8-bit binary: for example H = 01001000.
Page 106, 108
Unicode = one unified number for every character of every language, stored as UTF-8 or UTF-16. Unicode is a global standard that gives every character in any language a unified number, instead of a different system per language. With 2 bytes (16 bits) it can represent 65,536 characters and symbols.
Page 109, 110
Encode, store, decode. If the system differs, characters get corrupted. Encoding converts text into character codes using a given system, like Hello to 72 101 108 108 111. Decoding is the reverse: turning the stored numbers back into text a person can read.
Page 110, 111
The code decides which letter; the font decides its look: serif, sans-serif, semi-cursive. The character code decides which letter it is (65 = A), while the font decides how it looks on screen or in print. Serif: fonts with small strokes at the ends, like Times New Roman. Sans-serif: no strokes and clearer, like Arial.
Page 111, 113