6.2 else Statement

An alternative form of the if statement is:

if (condition)
    statement; 
else 
    statement;

If the condition is true, the first statement is executed. If it is false, the second statement is executed. In our accounting example, we wrote out a message only if nothing was owed. In real life, we probably want to tell the customer how much he owes if there is a balance due.

if (total_owed <= 0) 
    std::cout << "You owe nothing.\n"; 
else 
    std::cout << "You owe " << total_owed << " dollars\n"; 

Note to Pascal programmers: Unlike Pascal, C++ requires you to put a semicolon at the end of the statement before the else.

Now consider this program fragment:

if (count < 10)     // If #1 
    if ((count % 4) == 2)   // If #2
        std::cout << "Condition:White\n"; 
  else   // (Indentation is wrong)
      std::cout << "Condition:Tan\n"; 

There are two if statements and one else. To which if does the else belong? Pick one:

The correct answer is 3. According to the C++ syntax rules, the else goes with the nearest if, so 2 is syntactically correct. But writing code like this violates the KISS principle (Keep It Simple, Stupid). It is best to write your code as clearly and simply as possible. This code fragment should be written as follows:

if (count < 10) {       // If #1
    if ((count % 4) == 2)   // If #2 
        std::cout << "Condition:White\n"; 
    else 
        std::cout << "Condition:Tan\n"; 
} 

From our original example, it was not clear which if statement had the else clause; however, adding an extra set of braces improves readability, understanding, and clarity.