Pseudocode flowcharts
- 1. Pseudocode For Program Design 1
- 2. Flowcharts vs Pseudocode Flowcharts were the first design tool to be widely used, but unfortunately they do not reflect some of the concepts of structured programming very well. Pseudocode, on the other hand, is a newer tool and has features that make it more reflective of the structured concepts. The drawback is that the narrative presentation is not as easy to understand and/or follow. 2
- 3. Rules for Pseudocode Write only one statement per line Capitalise initial keyword Indent to show hierarchy and structures End multiline structures Keep statements language independent Remember you are describing a logic plan to develop a program, you are not programming! 3
- 4. One Statement Per Line Each statement in pseudocode should express just one action for the computer. Note capitals for the initial keywords Pseudocode READ name, hoursWorked, payRate gross = hoursWorked * payRate WRITE name, hoursWorked, gross These are just a few of the keywords to use, others include READ, WRITE, IF, ELSE, ENDIF, WHILE, ENDWHILE 4
- 5. Indent to Show Hierarchy Sequence: Keep statements in sequence all starting in the same column Selection: READ name, grossPay, taxes IF taxes > 0 IF, ELSE (or ELSEIF), ENDIF net = grossPay – taxes must be in line ELSE Indent all statements that depend net = grossPay on a condition ENDIF Loop: WRITE name, net count = 0 WHILE, ENDWHILE WHILE count < 10 Indent statements that fall inside ADD 1 to count the loop but not keywords that WRITE count form the loop ENDWHILE Also REPEAT, UNTIL WRITE “The End” 5
- 6. The Selection Structure yes no amount < 100 interestRate = .06 interestRate = .10 IF amount < 100 interestRate = .06 Pseudocode ELSE InterestRate = .10 ENDIF 6
- 7. The Looping Structure In flowcharting one of the more confusing things is to separate selection from looping. This is because each structure use the diamond as their control symbol. Pseudocode avoids this by using specific keywords to designate looping WHILE / ENDWHILE: condition checked before loop REPEAT / UNTIL: condition checked after loop 7
- 8. WHILE / ENDWHILE Start count = 0 WHILE count < 10 ADD 1 to count count = 0 WRITE count ENDWHILE WRITE “The End” count Mainline <10 Modular count = 0 Write WHILE count < 10 add 1 to “The End” count DO Process ENDWHILE Stop write count WRITE “The End” Process ADD 1 to count WRITE count 8
- 9. REPEAT / UNTIL Start count = 0 REPEAT count = 0 ADD 1 to count WRITE count UNTIL count >= 10 add 1 to WRITE “The End” count Mainline Modular write count count = 0 REPEAT DO Process count <10 UNTIL count >= 10 WRITE “The End” Write Process “The End” ADD 1 to count Stop WRITE count 9
- 10. Flowchart vs Pseudocode Flowchart Advantages: Pseudocode Advantages Standardized Easily modified Visual Implements structured concepts Done easily on Word Processor Flowchart Disadvantages: Pseudocode Hard to modify Disadvantages: Structured design elements Not visual not implemented No accepted standard, varies Special software required from company to company 10
- 11. Access of Data The READ statement tells the computer to get a value from an input device and store it in a memory location. How to deal with memory locations which have been allocated an address e.g. 19087 Give them names (field or variable names) Using descriptive words e.g. Total as opposed to a location addresses 11
- 12. Rules for Variable Names Begin with lowercase letter Contain no spaces Additional words begin with capital Unique names within code Consistent use of names 12
- 13. Working with Fields Calculations Selection + add > greater than - subtract < less than * multiply = equal to / divide >= greater than or equal to ** or ^ exponentiation <= less than or equal to () grouping <> not equal to 13