Algorithms and Their Properties
What is an algorithm, who carries it out, and what properties must it have? Everyday examples help us meet the key ideas behind algorithms.
All topics (1 of 11)
Chapter 1. Algorithm Basics
Chapter 2. Programming in Scratch
Chapter 3. Project Work
An algorithm is a precise sequence of steps that leads to a goal. Making tea or explaining the way to school are both algorithms. The person or device that carries out an algorithm is called the executor, and the actions it can perform are called commands.
Every algorithm should have several properties. Discreteness means the algorithm is divided into separate, complete steps. Clarity means the executor knows every command and can carry it out. Definiteness means each command has only one meaning, so the result does not depend on the executor’s wishes.
Effectiveness means the algorithm always gives a result after a finite number of steps. Generality means one algorithm can solve many problems of the same kind: the method for adding two numbers works for any two numbers. An algorithm can be written in words, as a flowchart or as a program.
Key takeaways
- An algorithm is a precise sequence of commands that leads to a goal.
- The one who carries out an algorithm is the executor, and it can perform only its own commands.
- Key properties: discreteness, clarity, definiteness, effectiveness and generality.
- An algorithm can be written in words, as a flowchart or as a program.
Practice tasks
- Write in your notebook an algorithm for brushing teeth using 6–8 commands.
- Which property of an algorithm is broken in the command “Put a little sugar in the tea”? Rewrite it as a precise command.
- Work in pairs: one of you writes an algorithm for the way to the school library, the other follows it as the executor and finds the unclear commands.
Review questions
Test yourself: think first, then reveal the answer.
1What is an algorithm?Show answerHide answer
A precise, step-by-step sequence of actions that leads to a goal.2What does the generality property of an algorithm mean?Show answerHide answer
One algorithm can solve many problems of the same kind.3Who or what is an executor?Show answerHide answer
A person or device that carries out an algorithm, such as a student or a computer.
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