C for beginners: The Decision Control Structure

The Decision Control Structure

We all need to alter our actions in the face of changing circumstances. If the weather is fine, then I will go for a stroll. If the highway is busy I would take a subway. If the pitch takes spin, we would win the match. If she says no, I would look elsewhere. You can notice that all these decisions depend on some condition being met.

C language too must be able to perform different sets of actions depending on the circumstances. In fact, this is what makes it worth its salt. C has three major decision making instructions (the if statement, the if-else statement and the switch statement). A fourth, somewhat less important structure is the one that uses conditional operators. In this section, we will explore all these ways (except switch we will talk about it in a different section) in which a C program can react to changing circumstances.


In the program written in the previous section, we’ve used sequence control structure in which the various steps are executed sequentially, i.e. in the same order in which they appear in the program. In fact to execute the instructions sequentially, we don’t have to do anything to do anything at all. By default, the instructions in a program are executed sequentially. However, in serious programming situations, seldom do we want the instructions to be executed sequentially. Many a times, we want a set of instructions to be executed in one situation and an entirely different set of instructions to be executed in another situation. This kind of situation is dealt in C programs using a decision control instruction. As mentioned earlier, a decision control instruction can be implemented in C using:

  • The if statement
  • The if-else statement
  • The conditional operators