• Programming is all about solving problems.

• It’s basically useless to develop a program with no purpose; thus programming is all about coming up with a solution to a problem.

• In programming, the series of steps taken in a particular order to solve a problem are known as an algorithm.

• The structure theorem explains that we express algorithms to solve problems using a combination of the following three elements:

1. Sequence – order imposed upon steps of an algorithm

2. Selection – coming up with a decision based upon some condition

3. Repetition – repeating one or steps of the algorithm a certain number of times until some condition is met.

Selection Control Structure

• For better functionality, programs are supposed to be able to make decisions.

• Selection Statements are used when making conditions about what task needs to be performed – based upon a certain condition.

• It allows the program to choose any one path from different sets of paths of execution based upon the outcome of an expression or state of a variable.

• In C, there are two selection statements: switch and if.

If Statement

• The statement inside the if statement block is executed only when the condition is true

• if syntax:

if (condition){
statement;
}

• if else syntax:

if (condition){
statement;
}
else{
statement;
}

• nested if else syntax:

if (condition){
    if (condition){
      statement;
    }
    else{
    statement;
    }
}
else{
    if (condition){
    statement;
    }
    else{
      condition;
      }
}

• if-else-if syntax:

if (condition_1)
{
statement;
}
else if (condition_2){
statement;
}
else if (condition_3){
statement;
}
else{
statement;
}

Switch Statement

• It is an alternative to the if-else-if statement which allows us to execute multiple operations for the different possible values of a single variable.

• switch can be used to select between alternative options just like the if else

NB: the switch construct is similar to the nested if-else but is more appropriate when different tasks must be selected – best for menus.

• switch syntax:

switch (expression)
{
case 1 :
    statement;
    break;
case 2:
    statement;
    break;
default:
    break statement;
    break;
}

Limitations of switch statement

1. Can only be used for integers and characters only.

2. It does not support ranges.

3. Suited for a limited number of options.

4. Operators cannot be used between switch statements.