Lesson Year 1 CS112/0401/V1 LESSON 6 DESIGN TOOL PSEUDOCODE  Program Design Language (PDL)  Represent logic in English-like manner  Easier to change

Lesson Year 1 CS112/0401/V1 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

Lesson Year 1 CS112/0401/V1 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

Lesson Year 1 CS112/0401/V1 SEQUENCE/SELECTION

Lesson Year 1 CS112/0401/V1 SELECTION

Lesson Year 1 CS112/0401/V1 SELECTION (CASE)

Lesson Year 1 CS112/0401/V1 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

Lesson Year 1 CS112/0401/V1 ITERATION

Lesson Year 1 CS112/0401/V1 PSEUDOCODE  The three basic program constructs  Sequence  Selection  Iteration

Lesson Year 1 CS112/0401/V1 PSEUDOCODE  Sequence  A series of statements (instructions)  Pseudocode convention –READ –WRITE –ACCEPT –DISPLAY –PRINT –INPUT –GET  Consistent use of conventions throughout pseudocode

Lesson Year 1 CS112/0401/V1 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 */

Lesson Year 1 CS112/0401/V1 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

Lesson Year 1 CS112/0401/V1 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.

Lesson Year 1 CS112/0401/V1 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

Lesson Year 1 CS112/0401/V1 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

Lesson Year 1 CS112/0401/V1 PSEUDOCODE /* compound condition */ e.g. IF marks >= 80 and marks <= 90 THEN class  ‘Second’ ENDIF

Lesson Year 1 CS112/0401/V1 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

Lesson Year 1 CS112/0401/V1 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 (indentation for easy reading)

Lesson Year 1 CS112/0401/V1 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

Lesson Year 1 CS112/0401/V1 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

Lesson Year 1 CS112/0401/V1 PSEUDOCODE Exercises 1.Write a pseudocode segment that reads 3 numbers A, B and C and display the biggest value of the three numbers.

Lesson Year 1 CS112/0401/V1 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