Pseudocode

GCSE Lesson - Pseudocode

1. Pseudocode

2. What is Pseudocode ? An informal way of writing a program High level description Text base Algorithmic

3. Common pseudocode notation INPUT – indicates a user will be inputting something OUTPUT – indicates that an output will appear on the screen WHILE – a loop (iteration that has a condition at the beginning) FOR – a counting loop (iteration) REPEAT – UNTIL – a loop (iteration) that has a condition at the end IF – THEN – ELSE – a decision (selection) in which a choice is made any instructions that occur inside a selection or iteration are usually indented

4. Mainly Three Processes Sequence Iteration Selection In the Order they need to happen Conditional statements

5. Sequence Summation of two numbers Input number1 Input number2 Total= number1+number2 Output total

6. Selection Two types of Selection Processes IF ... THEN ... ELSE ... CASE STATEMENT (SWITCH) Mainly used to process between two options Can compare more than two with multiple IF ELSEs Also can use as nested statements Mainly used to process between more than two options

7. IF ... THEN ... ELSE ... IF x>=1 then Print “x is positive”; ELSE IF x==0 then Print “x is 0” ELSE IF x<0 then Print “x is negative” END IF

8. If isDigit (x) then If x==0 then Print “x is o” Else if x>0 then Print “x is positive” Else Print “x is a character” Nested If Statements

9. Case Statement (Switch) CASE x OF 1: Do this thing 2: Do the other thing 3: Self-destruct ELSE Write “You must choose 1, 2 or 3” END CASE

10. Iteration Three types of Iteration Processes For loop Repeat Until While FOR count = 1 to 10 DO Write count x 3 NEXT count count = 1 REPEAT Write count x 3 count = count + 1 UNTIL count = 10 WHILE not eof ( StudentFile ) DO Read ( StudentFile ) Write surname,firstname,grade END WHILE

11. Question http:// www.bbc.co.uk/education/guides/z3bq7ty/test http://www.unf.edu/~ broggio/cop2221/2221pseu.htm