Computer Science Department FTSM Control Structure: Selection (Part 1) Knowledge: Understand various...

Computer Science Department FTSMFTSM

Control Structure: Control Structure: SelectionSelection(Part 1)(Part 1)

Knowledge:Understand various concepts of selection control structure

Skill:Be able to develop a program containing selection control structure

TK1913-C ProgrammingTK1913-C Programming 22

Selection StructureSelection Structure

Single Single SelectionSelection

Double SelectionDouble Selection

Multiple Multiple SelectionSelection


Single SelectionSingle Selection

Pseudocode StructurePseudocode Structure

step a

if <condition is true> startstep mstep n

end_ifstep x


step a


end_ifstep x


Single SelectionSingle Selection

Step aStep a

conditioncondition Step mStep m

Step nStep n

Step xStep x

truetrue

falsefalse

Step aStep a


Step nStep n

Step xStep x

truetrue

falsefalse


ExerciseExerciseDevelop an algorithm for the following problem:

A system to check/verify the eligibility of a person to vote during the election is going to be developed. The input for the system is the person’s age.

If the age is greater than 20 years old, then display “You are eligible to vote” and “Your age is <age> years old” messages.

If the age is less than 20 years old, display “Your age is <age> years old” message only.


Exercise - Answer Exercise - Answer

truetrue

falsefalse

““You are You are eligible to vote”eligible to vote”

ageage

startstart

endend

““Your age is <age> Your age is <age> years old”years old”

age > 20age > 20truetrue

falsefalse


ageage

startstart

endend


age > 20age > 20

Assume the age is Assume the age is 12 years old12 years old

12 > 20 ? 12 > 20 ? FALSE !FALSE !

Your age is 12 Your age is 12 years oldyears old


Something to ponder …Something to ponder …

the age is 37 years old?What if …..

What about 20 years old?


Let’s recap …Let’s recap …


step a


end_ifstep x


step a


end_ifstep x


Double selection has similar Double selection has similar structure except that …structure except that …




step aif <condition is true> start

step mstep n

end_ifelse start

step xstep y

end_elsestep z



step mstep n

end_ifelse start

step xstep y

end_elsestep z

… … additional additional steps at the steps at the bottom …bottom …



Step aStep a


Step nStep n

Step zStep z

truetrue

falsefalse

Step xStep x

Step yStep y

Step aStep a


Step nStep n

Step zStep z

truetrue

falsefalse

Step xStep x

Step yStep y


ExerciseExerciseDevelop an algorithm for the following problem:

A system to check/verify the eligibility of a person to vote during the election is going to be developed. The input for the system is the person’s age.

If the age is greater than 20 years old, then display “You are eligible to vote” and “Your age is <age> years old” messages.

If the age is less than 20 years old, display “You are not eligible to vote” and “Your age is <age> years old” messages.


Exercise - Answer Exercise - Answer

truetrue

falsefalse


ageage

startstart

endend


age > 20age > 20

Verify this Verify this flowchart !flowchart !

““You are not You are not eligible to vote”eligible to vote”


Let’s recap …Let’s recap …


step a


end_ifstep x


step a


end_ifstep x




step mstep n

end_ifelse start

step xstep y

end_elsestep z



step mstep n

end_ifelse start

step xstep y

end_elsestep z

Double Double SelectionSelection

Guess…how does multiple Guess…how does multiple selection look like ?selection look like ?


Multiple SelectionMultiple Selection

Pseudocode Structure (Multi-way if)Pseudocode Structure (Multi-way if)

step aif <condition_1 is true> start

step mend_ifif <condition_2 is true> start

step nend_if

step z

Pseudocode Structure (Multi-way if)Pseudocode Structure (Multi-way if)

step aif <condition_1 is true> start

step mend_ifif <condition_2 is true> start

step nend_if

step z



Step aStep a

Condition1Condition1 Step mStep m

Step nStep n

Step zStep z

truetrue

falsefalse

Condition2Condition2truetrue

falsefalse

Step aStep a


Step nStep n

Step zStep z

truetrue

falsefalse


falsefalse



Pseudocode Structure (Cascaded if)Pseudocode Structure (Cascaded if)step aif <condition_1 is true> start

step mend_if

if <condition_2 is true> startstep n

end_ifelse start

step xend_elsestep z

Pseudocode Structure (Cascaded if)Pseudocode Structure (Cascaded if)step aif <condition_1 is true> start

step mend_if

if <condition_2 is true> startstep n

end_ifelse start

step xend_elsestep z



Step aStep a


Step nStep n

Step zStep z

truetrue

falsefalse


falsefalse

Step xStep x

Step aStep a


Step nStep n

Step zStep z

truetrue

falsefalse


falsefalse

Step xStep x


ExerciseExerciseDevelop a flowchart for the following problem.

Given a mark, determine its grade based on the table below:

74 < mark < 100 grade = A64 < mark < 75 grade = B54 < mark < 65 grade = C39 < mark < 55 grade = D 0 < mark < 40 grade = E others error message


End of Lecture 7 (Part 1)End of Lecture 7 (Part 1)

Yes !! That’s all? Yes !! That’s all? What’s next???What’s next???

PART 2PART 2 on the way… on the way… relax !relax !

Computer Science Department FTSM Control Structure: Selection (Part 1) Knowledge: Understand various...

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