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Exploring computer science

How does a computer store numbers and pictures? How does encryption work, and how does a search engine find the right thing in a fraction of a second? Here you learn topics from computer science class – and try everything out directly with Python. You need loops, lists and functions from the Python section.

0 of 5 lessons done

Chapter 1Data

  1. 01
    35 minutes

    Binary numbers, bits and bytes

    Understand why computers only calculate with 0 and 1 · Convert numbers between the decimal and the binary system · Know how letters are stored as numbers

Chapter 2Encryption

  1. 02
    45 minutes

    Secret codes – Caesar and Vigenère

    Understand and program the Caesar cipher · See why Caesar is easy to crack · Encrypt more securely with a keyword using Vigenère

Chapter 3Data

  1. 03
    40 minutes

    Pictures are made of pixels

    Store a picture as a list of rows with brightness values · Understand how colours are made from red, green and blue · Program your own image filters

Chapter 4Algorithms

  1. 04
    45 minutes

    How does a search engine work?

    Understand why search engines don't read every page one by one · Build an index of words and pages · Use sets to find pages that contain several words

  2. 05
    40 minutes

    How fast is an algorithm?

    Count a program's steps instead of timing it · See how the number of steps grows when the data gets twice as big · Replace a slow algorithm with a fast one