JSP (Jackson Structured JSP (Jackson Structured Programming)Programming)Lesson 7 – Program Concepts

JSP (Jackson Structured JSP (Jackson Structured Programming)Programming)Methodology developed by Michael

Anthony Jackson in 1970

Uses top-down methodology

3 structured constructs

◦Sequence

◦Selection

◦Iteration/Repetition

SequenceSequence

A seqBCD

A end

A sequence of operations is represented by boxes connected with lines. In the example below, operation A consists of the sequence of operations B, C and D

SelectionSelection

IF C1 THEN

DO B

ENDDO

ELSE

IF C2 THENDO CENDDO

ELSEIF C3 THEN

DO DENDDOENDIF

A sequence of operations is represented by boxes connected with lines. In the example below, operation A consists of the sequence of operations B, C and D

IterationIteration

WHILE condition 1DO B

ENDDO

An iteration is again represented with joined boxes. In addition the iterated operation has a star in the top right corner of its box. In the example below, operation A consists of an iteration of zero or more invocations of operation B.

Example: SequenceExample: Sequence

MainControl

Initial Body End

Example: SelectionExample: Selection

Check AgeModule

Teenage Module0 Adult Module0

Where C1 is Age < 21

C1

Example: IterationExample: Iteration

Main Process

Detail Process

While C1

C1 is not end of file

JSPJSPFunction list

◦Sequence of actions listedCondition list

◦Associated with selections and iterations

Note: function & condition lists are listed separately from the structure diagram and are cross-referenced

JSPJSPStepwise Refinement

◦A process to sub-divide (refine) the main program function into subsidiary functions

◦Increasing the details at each level until the lowest functions are represented

JSPJSPCase StudyA program is needed to help a college to grade its students. A total weighted score is determined for students from two midterm exam scores both weighted at 30%, and a final exam score at 40%. A grade is assigned on the following basis:Total weighted score Grade <60 F >=60 and <70 D >=70 and <80 C >=80 and <90 B >=90 AFor each student, the program is to output the student number, the total weighted score and the grade assigned. It is also required to count the number of students receiving each of the five grades. The input will be in the form of a record, each consisting of student number, midterm test 1, midterm test 2 and final test mark. The iteration is to be terminated by a suitable dummy record. The summary will then be printed showing the distribution of the grades. Draw the JSP.

Case StudyCase StudyMAIN-CTRL

INITIAL BODYEND

1,213,14 WHILE C1

PROCESS *

A o

OUTPUT &NEXT

RECORD

ASSIGNCALCULATIONINPUTRECORD

F oD o

C oB o

3

4

6 7 89

10

11,12

5

C2

C3 C4 C5

Function ListFunction List1 : Initialise all variables, counters2 : Get first record3 : Input record4 : Total Weighted score = 30% x Midterm Test 1+

30% x Midterm Test 2 + 40% x Final Test 5 : Assign grade 6 : Increase Counter A by 17 : Increase Counter B by 18 : Increase Counter C by 1 9 : Increase Counter D by 110 : Increase Counter F by 1 11 : Print Student Number, Weighted Score and

Grade.12 : Get next record13 : Print Summary Record14 : End Program

Condition ListCondition List

C1 : Not EOFC2 : Total weighted score >= 90C3 : Total weighted score >= 80C4 : Total weighted score >= 70C5 : Total weighted score >= 60

(Note to Lecturers: This is an easier solution as compared to the study guide, but acceptable for examination purposes.)