Selection Control Structures


In selection control structures, conditional statements are features of a programming language which perform different computations or actions depending on whether a programmer-specified Boolean condition evaluates to true or false.[1]


The basic attribute of a selection control structure is to be able to select between two or more alternate paths. This is described as either two-way selection or multi-way selection. A question using Boolean concepts usually controls which path is selected. All of the paths from a selection control structure join back up at the end of the control structure, before moving on to the next lines of code in a program.

If Then Else Control Structure

The if then else control structure is a two-way selection.

If age > 17
    Output "You can vote."
    Output "You can't vote."
Language Reserved Words
C++ if, else
C# if, else
Java if, else
JavaScript if, else
Python if, elif, else
Swift if, else

Case Control Structure

The case control structure is a multi-way selection. Case control structures compare a given value with specified constants and take action according to the first expression to match.[2]

Case of age
    0 to 17   Display "You can't vote."
    18 to 64  Display "You're in your working years."
    65 +      Display "You should be retired."
Language Reserved Words
C++ switch, case, break, default
C# switch, case, break, default
Java switch, case, break, default
JavaScript switch, case, break, default
Python N/A
Swift switch, case, break (optional), default

Python does not support a case control structure. There are workarounds, but they are beyond the scope of this book.

Key Terms

if then else
A two-way selection control structure.
A multi-way selection control structure.



Icon for the Creative Commons Attribution-ShareAlike 4.0 International License

Programming Fundamentals Copyright © 2018 by Authors and Contributors is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

Share This Book