11.1. Making Decisions

We have discussed two major features used by computer algorithms. We can name values and we can repeat steps. The third major tool we can use to build algorithms is the ability to make decisions.

We make decisions all the time. Before we leave the house we may check to see if it will rain that day, and if it will, we bring an umbrella.


Algorithms also often need to make decisions about what actions to take. If a computer is processing an order and a credit card is valid then charge the card, otherwise it needs to ask for a new credit card. The computer’s ability to take action (execute some code) when something is true is also called conditional execution.

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