Structured English specification.

Structured English specification

PROCESS SPECIFICATION

Once a DFD is obtained the next step is to precisely specify the process. Structured English, Decision tables and Decision Trees are used to describe processes. Decision tables are used when the process is logically complex involving large number of conditions and alternate solutions. Decision trees are used when conditions to be tested must follow a strict time sequence.

STRUCTURED ENGLISH

Structured English is similar to a programming language such as Pascal. It does not have strict syntax rules as in programming languages as the intention is only to give precise description of a process. The structured English description should be understandable to the user.

DECISION TABLE-EXAMPLE

Same structured Englis          edure given as decision table

DECISION TABLE-EXPLANATION

• Conditions are questions to be asked

• ‘Y’ is yes,’N’ is no & ‘-’ is irrelevant

• A ‘X’ against the action says the action must be taken

• A ‘-’ against the action says the action need not be taken

Rule 2 in decision table DISCOUNT states:

if no advance payment and purchase amount >=10000

and regular customer then give 5% discount

In Structured English, imperative sentences, actions to be performed should be precise and quantified

Good Example: Give discount of 20%

Bad Example: Give substantial discount

The operators and keywords in Structured English are as follows:

until, while, do, case, for, search, retrieve, read, write Delimiters – {, }, end, end if, end for The structured English procedure given above is expressed as a Decision tree below

STRUCTURED ENGLISH-DECISION STRUCTURES

If condition then

{ Group of statements }

else

{ Group of statements }

end if

Example: if(balance in account >= min.balance)

then honor request

else reject request

end if

STRUCTURED ENGLISH-CASE STATEMENT

Case (variable)

Variable = P: { statements for alternative P}

Variable = Q: { statements for alternative Q}

Variable = R: { statements for alternative R}

None of the above: { statements for default case}

end case

Example : Case(product code)

product code =1 : discount= 5%

product code =2 : discount =7%

None of the above : discount=0

end case

STRUCTURED ENGLISH-REPETITION STRUCTURE

for index = initial to final do

{ statements in loop }

end for

Example : Total =0

for subject =1 to subject =5 do

total marks=total marks +marks(subject)

write roll no,total marks

end for

STRUCTURED ENGLISH-WHILE LOOP

while condition do

{ statements in loop }

end while

Example : while there are student records left do

read student record

compute total marks

find class

write total marks, class, roll no

 end while

EXAMPLE