The Four Pillars of Computational Thinking, Applied to a Cashier App
Jeannette Wing of Carnegie Mellon University described computational thinking as framing a problem so that its solution can be carried out by an information processor. Its four pillars are decomposition, pattern recognition, abstraction and algorithm design. In Indonesia, Informatics is now a compulsory lower-secondary subject under the Merdeka Curriculum, so many students meet these terms well before they write their first line of code.
A cashier app shows all four pillars at work. Decomposition splits the app into three jobs: recording item prices, adding up the total and printing a receipt. Pattern recognition notices that a 10 percent discount and a 20 percent discount follow the same formula with a different number plugged in. Abstraction strips away details that never affect the sum, such as packaging colour or which cashier is on shift. Algorithm design then arranges what remains into a sequence that always gives the same output for the same input.
None of this needs a computer at first. A learner can write out the steps for making a cup of tea in recipe-level detail and then hunt for any step quietly taken for granted, such as how anyone knows the water has boiled. Bebras challenge tasks fit this stage well, testing order and pattern through stories about beavers, maps and stacked boxes without a single line of syntax. Adults who think of themselves as having no head for logic often discover that what they lacked was simply the habit of spelling every step out.
Once a task can be written out completely in plain sentences, turning it into code becomes a question of vocabulary.