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LESSON 6 DESIGN TOOL PSEUDOCODE

LESSON 6 DESIGN TOOL PSEUDOCODE. Program Design Language (PDL) Represent logic in English-like manner Easier to change. Rules for Pseudocode. Language independent Indentation for readability Key words in capital letters Punctuation optional IF ends with ENDIF

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LESSON 6 DESIGN TOOL PSEUDOCODE

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  1. LESSON 6DESIGN TOOLPSEUDOCODE • Program Design Language (PDL) • Represent logic in English-like manner • Easier to change

  2. Rules for Pseudocode • Language independent • Indentation for readability • Key words in capital letters • Punctuation optional • IF ends with ENDIF • Ends DO, DO WHILE, DO FOR with ENDDO • Main routine shown first

  3. Advantage of Pseudocode • Bridges gap between human language & computer language • Logic expressed in straightforward way • Easy to understand • Good design tool • Easier to make changes • Allow structured walkthroughs

  4. SEQUENCE/SELECTION

  5. SELECTION

  6. SELECTION (CASE)

  7. SELECTION (CASE) DO CASE CHOICE-A DO MOD-E ENDDO CHOICE-B DO MOD-F ENDDO CHOICE-C DO MOD-G ENDDO CHOICE-D DO MOD-H ENDDO ENDCASE

  8. ITERATION

  9. PSEUDOCODE • The three basic program constructs • Sequence • Selection • Iteration

  10. PSEUDOCODE • Sequence • A series of statements (instructions) • Pseudocode convention • READ • WRITE • ACCEPT • DISPLAY • PRINT • INPUT • GET • Consistent use of conventions throughout pseudocode

  11. PSEUDOCODE • Pseudocode convention Comments Statements that are non-executable Indication: /*…*/ e.g. /* Comment aids legibility */ e.g. /* This is an example of a long comment */

  12. PSEUDOCODE • Pseudocode Convention • Iteration: REPEAT…UNTIL To repeat a given set of commands Condition is checked after actions REPEAT commands UNTIL condition e.g. REPEAT ACCEPT number cube  number ** 3 DISPLAY number, cube UNTIL number = 0

  13. PSEUDOCODE • Pseudocode Convention • Do not use equal sign in assignment statements. • Use  in assignment statements or words ‘set to’ • Use ‘=‘ sign only in conditional statements.

  14. PSEUDOCODE • Pseudocode Convention • Iteration: FOR loop For fixed number of iterations FOR index IN RANGE min TO max DO commands ENDDO e.g. FOR I IN RANGE 1 to 10 DO PRINT I, I**2 ENDDO

  15. PSEUDOCODE • Pseudocode Convention • Selection: IF…THEN Carry or ignore commands based on condition IF condition THEN commands ENDIF /* simple condition */ e.g. IF marks > 90 THEN class  ‘First’ ENDIF

  16. PSEUDOCODE /* compound condition */ e.g. IF marks >= 80 and marks <= 90 THEN class  ‘Second’ ENDIF

  17. PSEUDOCODE • Pseudocode Convention • IF-THEN-ELSE…ENDIF To select one of two or more alternative commands depending on a given condition IF condition THEN command sequence 1 ELSE command sequence 2 ENDIF e.g.IF marks >= 50 THEN remarks  ‘Pass’ ELSE remarks  ‘Fail’ ENDIF

  18. PSEUDOCODE • Pseudocode Convention • Multi-way selection Further extension of IF-THEN-ELSE construct to allow multiple selection IF condition 1 THEN command sequence 1 ELSE IF condition 2 THEN command sequence 2 ELSE IF condition 3 THEN command sequence 3 ENDIF ENDIF ENDIF (indentation for easy reading)

  19. PSEUDOCODE • Pseudocode Convention • Selection: Multi-way selection CASE…ENDCASE DO CASE of index CASE index condition 1 command sequence 1 CASE index condition 2 command sequence 2 CASE index condition 3 command sequence 3 OTHERWISE command sequence ENDCASE

  20. PSEUDOCODE • Pseudocode Convention • Selection: Multi-way / selection CASE…ENDCASE e.g. DO CASE OF menu_choice CASE ‘E’ DO enquiry routine ENDDO CASE ‘U’ DO update routine ENDDO CASE ‘X’ EXIT menu ENDDO OTHERWISE DISPLAY error message ENDCASE

  21. PSEUDOCODE Exercises 1. Write a pseudocode segment that reads 3 numbers A, B and C and display the biggest value of the three numbers.

  22. PSEUDOCODE Exercises 2. Write a pseudocode segment for a program that calculates the BONUS on a salesman’s sale. Zero if SALES is less than $2000 Ten percent of SALES if amount is between $2000 to $4000 Five percent of SALES plus $1000 if amount is $4000 or above

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