1. Writing algorithms
Introduction to Python

2. Learning objectives Learn to write algorithms in pseudocode
Review the difference between syntax errors, run- time errors and logic errors
Learn techniques for debugging programs

3. What does this algorithm do?
#GhostHunter
if ghost catches man then
lives  lives – 1
if lives = 0 then
display "Game Over!"
else
display "Arghhh!"

4. Use it to plan before coding!
Writing Pseudocode
Pseudocode is half code, half English
It has no real syntax and would not run
It is a structured sequence of instructions
It is useful for planning algorithms
Use it to plan before coding!

5. Suggested language for Pseudocode
Use indentation in pseudocode
Use words such as:
print, display, input, output, calculate, add, set, reset, if, then, else

6. Pseudocode Example: if unlock button pressed then
display PIN unlock screen
input PIN
if correct PIN entered then
unlock phone
else display “Try again”
else display lock screen

7. Anything in between = Medium
Writing an Algorithm
Write a pseudocode algorithm to display the correct hat size based on the circumference of your head:
Less than 57cm = Small
Greater than 60cm = Large
Anything in between = Medium

8. Now write the code… You should understand the problem more clearly
It should be easier to write – in any language!

9. Types of programming error
Syntax Errors
Run-Time Errors
Logic Errors

10. Debugging exercise TaxCalculatorBUGS.py
Look at the two programs below and see if you can find and correct the errors in them
SeasonFinderBUGS.py
TaxCalculatorBUGS.py