Algorithm design tools

9 System design

9.1 Top-down design 9.2 Structure diagrams

102 102 9.3 Design steps 105 9.4 The complete design process 109

10 Arrays

10.1 Declaring an array 10.2 Initialising arrays 10.3 Using arrays 10.4 Groups of arrays 10.5 Two-dimensional arrays 10.6 Array reference for implementation in Python

11 Checking inputs

11.1 Validation 11.2 Verification 11.3 Programming validation into your systems

12 Testing

12.1 When to test 12.2 Debugging 12.3 IDE debugging tools and diagnostics 12.4 Identifying logical errors 12.5 Dry running 113 114 114 126 128

131

136 137

137

152 152

154 156 156 12.6 Breakpoints, variable tracing and stepping through code 12.7 Beta testing

13 Files and databases

13.1 Files 13.2 Databases 13.3 Querying databases 13.4 Python and SQL 13.5 More advanced SQL 161 164

168 171 173 178 179

14 Programming scenario task

14.1 Reading the question 184 14.2 Constructing a skeleton answer 185 14.3 Filling in the details 186 14.4 Putting it all together 188 14.5 Final thoughts 189

15 Examination practice 194 Appendix 1: Turtle reference 205 Appendix 2: Tkinter reference 207 Glossary 211 Acknowledgements 214 Solutions