Pseudocode and Flowcharts

Assignment

Assignment Values are assigned to an item/variable using the ← operator. The variable on the left of the ← is assigned the value of the expression on the right

Conditional statements

A condition that can be true or false: IF … THEN … ELSE … ENDIF

Example: IF Age < 18

THEN PRINT “Child”

ELSE PRINT “Adult”

ENDIF

A choice between several different values: CASE … OF … OTHERWISE … ENDCASE, for example

CASE Grade OF

“A”: PRINT “Excellent”

“B”: PRINT “Good”

“C”: PRINT “Average”

OTHERWISE PRINT “Improvement is needed”

ENDCASE

IF … THEN … ELSE … ENDIF

For an IF condition the THEN path is followed if the condition is true and the ELSE path is followed if the condition is false. There may or may not be an ELSE path. The end of the statement is shown by ENDIF.

Example: IF Found

THEN PRINT “Your search was successful”

ELSE PRINT “Your search was unsuccessful”

ENDIF

CASE … OF … OTHERWISE … ENDCASE

For a CASE condition the value of the variable decides the path to be taken. Several values are usually specified. OTHERWISE is the path taken for all other values. The end of the statement is shown by ENDCASE.

Example: CASE Choice OF

1 : Answer ← Num1 + Num2

2 : Answer ← Num1 – Num2

3 : Answer ← Num1 * Num2

4 : Answer ← Num1 / Num2

OTHERWISE PRINT “Please enter a valid choice”

ENDCASE

Loop structures

When some actions performed as part of an algorithm need repeating, this is called ‘iteration’. Loop structures are used to perform the iteration.

FOR … TO … NEXT

FOR Counter ← 1 TO 10

PRINT “*”

NEXT Counter ← 0

REPEAT … UNTIL

REPEAT

PRINT “*”

Counter ← Counter + 1

UNTIL Counter > 10

WHILE … DO … ENDWHILE

Counter ← 0

WHILE Counter < 10 DO

PRINT “*”

Counter ← Counter + 1

ENDWHILE

Input and output statements

INPUT and OUTPUT are used for the entry of data and display of information

INPUT is used for data entry. It is usually followed by a variable where the data input is stored, for example:

INPUT Name

INPUT StudentMark

OUPUT/PRINT is used to display information either on a screen or printed on paper.

PRINT Name

PRINT “Your name is”, Name

OUTPUT Name1, Name2, Name3

Standard flowchart symbols

Flowcharts are drawn using standard symbols.