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The GNU C Programming Tutorial - Decisions

Node:Decisions, Next:, Previous:Pointers, Up:Top


Testing and Branching. Making conditions.

Until now, our code examples have been linear: control has flowed in one direction from start to finish. In this chapter, we will examine ways to enable code to make decisions and to choose among options. You will learn how to program code that will function in situations similar to the following:

  • If the user hits the jackpot, print a message to say so: You've won!
  • If a bank balance is positive, then print C for "credit"; otherwise, print D for "debit".
  • If the user has typed in one of five choices, then do something that corresponds to the choice, otherwise display an error message.

In the first case there is a simple "do or don't" choice. In the second case, there are two choices. The final case contains several possibilities.

C offers four main ways of coding decisions like the ones above. They are listed below.


if (condition)
  do something


if (condition)
  do something
  do something else


(condition) ? do something : do something else;


switch (condition)
  case first case : do first thing
  case second case : do second thing
  case third case : do third thing

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