Program Control Structures

Program Control Structures

1. Selection

   • The sequence of instructions can be changes based on the value of variables within that program. Statements are selected based on a value through the use of IF statements and boolean operators
     • IF- Statement
       • Whnen a condition in an IF-statement evaluates to true, the statements follwing it are executed, otherwise the statements following ELSE are executed.

2. Iteration

   • "Repetition"; when a section of code is carried out more than once.
     • Unconditional repetition
       • There is a start value and a stop value for the loop. The loop is incremented by 1 (default) each time.
       • Example: a program to output all the multiples of three between 3 and 99 will repeat the loop 97 times.
     • Conditional repetition
       • The loop will run until a particular condition is true or false..
       • Example: a program to ensure that a user enteres a integer value between 1 and 50. A boolean variable can be used to control the loop.
   • Loops and conditions are used to repeat the sections of code.
     • FOR Loop: for(initialise, condition, increment)
       • for(int i = 0, i < totalTime, i++)
       • initialise: variable is set to the starting value of the loop once only
       • condition: this is evaluated during each execution of the loop
       • increment: updates the loop control variable
     • WHILE Loop: While (Boolean Condition) do
       • A boolean condition has to be met (true or false) for the loop to execute, and will run until the boolean condition is the opposite - true or false
       • A loop can also test the condition at the end of the loop. This means the code will be executed at least once.

3. Sequence

   • This denotes the order in which instructions are carried out. Each statement is carried out one after the other.
     • Incorrect Example:
       • This example is trying to output the average before the numbers have been entered and running this would result in a logic error.
     • Correct Example:

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