Use of IF condition/selection statement
IF pass = true THENSEND “Well done, you have passed” TO DISPLAYEND IFIn the following example it is necessary to use the ELSE command because the statement has two possible selections/outcomes.
IF pass = true THENSEND “Well done, you have passed” TO DISPLAYELSESEND “Unfortunately, you did not pass the test” TO DISPLAYEND IFIteration v repetition (loops)
Iteration takes place when the values held within an array are used/examined/processed in order, one after the other.
Repetition is any other form of loop that repeats a series of commands a set number of times. Repetition can be both fixed and conditional.
Iteration – FOR loops
It is important to note that indexing starts from 0 and not 1, unless otherwise stated. This can be seen here where the counter is set to repeat ten times (0 TO 9 rather than 1 TO 10).
FOR counter FROM 0 TO 9 DOIF score [counter] > maximum THENSET maximum TO score[counter]END IFEND FORThe other version of a FOR loop is more generic in nature as there is no requirement to set the lower and upper bounds of the index.
FOR EACH score FROM allScores[] DOIF score > maximum THENSET maximum TO scoreEND IFEND FOR EACHThis would take each score held in the array allScores in order and perform the commands found within the loop.
Repetition – fixed repetition (REPEAT)
The distinction between fixed repetition and iteration is that fixed repetition can repeat a set of commands without needing to iterate over the values of a data structure like an array.
REPEAT 5 TIMESSEND “Game Over” TO DISPLAYEND REPEATThis would send the string text 'Game Over' to the display five times:
Game OverGame OverGame OverGame OverGame OverRepetition – conditional repetition (WHILE and REPEAT…UNTIL)
There are two forms of conditional repetition. The first is known as pre-condition repetition and will only allow the loop to execute if the condition it is set up to check is true. For this purpose a WHILE loop can be used.
WHILE percentage <0 OR percentage >100 DOSEND “The percentage you entered is not valid. Please try again.” TO DISPLAYRECEIVE percentage FROM (REAL) KEYBOARDEND WHILEThe loop will only execute if the value of the percentage variable is less than 0 or greater than 100.
