Conditional Statements in C++

The If Statement

• Basic structure involves checking a condition and executing code based on whether the condition is true or false.

Multiple Alternatives

• Multiple if statements can be combined to evaluate complex decisions.
• Use multiple if statements to implement multiple alternatives.
• Order matters: Pay attention to the order of conditions in multiple if statements.

Example: Richter Scale

• Multiple branches for different descriptions of damage based on the Richter scale value.
• Code example:

  if (richter >= 8.0) {
    cout << "Most structures fall";
  } else if (richter >= 7.0) {
    cout << "Many buildings destroyed";
  } else if (richter >= 6.0) {
    cout << "Many buildings considerably damaged, some collapse";
  } else if (richter >= 4.5) {
    cout << "Damage to poorly constructed buildings";
  } else {
    cout << "No destruction of buildings";
  }

• If a test is false, that block is skipped, and the next test is made.
• As soon as one test succeeds, its block is executed, and no further tests are attempted.

The Switch Statement

• Used for a sequence of if statements that compares a single value against several constant alternatives.
• Can only be used with integer or character types.
• Example:

  int digit;
  switch (digit) {
    case 1: digit_name = "one"; break;
    case 2: digit_name = "two"; break;
    case 3: digit_name = "three"; break;
    case 4: digit_name = "four"; break;
    case 5: digit_name = "five"; break;
    case 6: digit_name = "six"; break;
    case 7: digit_name = "seven"; break;
    case 8: digit_name = "eight"; break;
    case 9: digit_name = "nine"; break;
    default: digit_name = ""; break;
  }

• The default branch is chosen if none of the cases matches.
• Every branch of the switch must be terminated by a break statement.
• If the break is missing, execution falls through to the next branch.

Common Error

• Forgotten break in switch statement can lead to unintended fall-through.
• Many programmers consider the switch statement somewhat dangerous and prefer the if statement.