PM Chap 6 - Pseudo-Code

8/8/2019 PM Chap 6 - Pseudo-Code

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Format ExplanationThis is the where procedures,variables, types, etc., aredeclared

○ Declares the names, types,etc., of procedures , variables.

This is the area where processing is described.

●Variable←Expression Assigns the value of theexpression to the variable.

Pseudo-Code Description Format

Declarationsection

Processingsection

Format Explanation{comment} Used for comments.

● Process 1

● Process 2

Indicates selective processing.

If the conditionalexpression is true, Process1 is executed; if theconditional expression isfalse, Process 2 isexecuted.

● Process

Indicates a loop with thetermination condition attop.

The process is executedas long as the conditionalexpression is true.

Conditionalexpression

Conditionalexpression



Example 1 “2 Branch”When mathematics score is less than 60, the student gets imposed

report problem.

SCORE 60

Mathematics Exam.

Report Problem

Yes

No

Declaration

section

○ Integer Variable: SCORE

● SCORE ← Mathematics Mark

Processing

sectionScore 60● Report Problem

● Do Nothing



Example 2 “3 Branch”When mathematics score is less than 60, and English score is less

than 60, the student gets imposed report problem.

Math. SCORE 60

Mathematics Exam.

Yes

No

English Exam.

Eng. SCORE 60

ReportProblem

Yes

No

Declaration

section

○ Integer Variable: Math.SCORE,Eng.SCORE

● Math.SCORE ← Mathematics Mark

Processing

section

Math.Score 60

● Report Problem

● Do Nothing

● Eng.SCORE ← English Mark

Eng.Score 60

● Do Nothing



When mathematics score is less than 60, or English score is less

than 60, the student gets imposed report problem.

Example 3 “3 Branch”

Math. SCORE 60

Mathematics & English Exam.

Yes No

ReportProblem

Yes

No

Eng. SCORE 60

ReportProblem

Declaration

section

○ Integer Variable: Math.SCORE,Eng.SCORE


Processing

section

Math.Score 60● Report Problem

● Do Nothing

● Eng.SCORE ← English Mark

Eng.Score 60

● Do Nothing

● Report Problem



Example 4 “3 Branch”When mathematics score is greater than equal 80 evaluation A,

when score is less than 80 and greater than equal 60 evaluation B,when score is less than 60 then evaluation C.

Declarati

onsection

○ Integer Variable: Math.SCORE


Processing

section

Math.Score 80≧

● Evaluation A

● Evaluation C

Math.Score 60≧

● Evaluation B

Math. SCORE

Mathematics Exam.

80 Score≦ Score 60

Evaluation A

60 Score≦ 80

Evaluation B

Evaluation C



Example 5 “Repeat”Variable x has an initial value 0. And add 1 to x. It repeats addition

while x is not 5 (until x becomes 5).

X ≠ 5

X ← 0

No

Yes

X ← X+ 1

Declaration

section

○ Integer Variable: X

● X ← 0

Processing

section

X ≠5

● X = X + 1



Example 6 “Loop”Variable x has an initial value 0. And add 3 to x. It repeats addition 5

times.

Y 5

X ← 0, Y ← 0

No

Yes

X ← X + 3

Y ← Y + 1

Y becomes the Loop Counter.

Declaration

section

○ Integer Variable: X, Y

● X ← 0

Processing

section Y 5

● X = X + 3

● Y ← 0

● Y = Y + 1



Example 7 “Loop”Calculate the sum of odd number 1, 3, 5, 7, and 9.

Declaration

section


● X ← 0

Processing

section Y 9≦

● X = X + Y

● Y ← 1

● Y = Y + 2

X ← 0, Y ← 1

X ← X + Y

Y ← Y + 2

Looptill Y > 9

Loop



Practice 1

Sum of integer 1 to 10

i 10≦

Sum ← 0, i ← 1

No

Yes

Sum ← Sum + i

i ← i + 1

Declaration

section

○ Integer Variable: Sum, i

● Sum ← 0

Processing

section i 10≦

● Sum = Sum + i

● i ← 1

● i = i + 1



Example 8 “Loop Array”There are four money savings boxes. Their name are "week1",

"week2", "week3", and "week4".Get the total amount of money at the end of the month.

i 4≦

Save(1) ← 120, Save(2) ← 340Save(3) ← 230, Save(4) ← 180

Sum ← 0, i ← 1

No

Yes

Sum ← Sum + Save(i)

i ← i + 1

Declaration

section

○ Integer Variable: Sum, i

● Save(1)← 120 ~ Save(4) ← 180

Processing

section i 4≦

● Sum = Sum + Save(i)

● Sum ← 0, i ← 1

● i = i + 1

○ Integer Array: Save(4)





Example 7 “Loop”Calculate the sum of odd number 1, 3, 5, 7, and 9.

Y 9≦

X ← 0, Y ← 1

No

Yes

X ← X + Y

Y ← Y + 2

Declaration

section


● X ← 0

Processing

section Y 9≦

● X = X + Y

● Y ← 1

● Y = Y + 2



Practice 2

As for array T(n), a different inascending order value is stored.Variable "data" was given now.Look for the same value as "data"from this array by the binarysearch method.



Practice 2

T(1) T(2) T(3) … … … T(n-1) T(n)

low ← mid →high

Before

T(1) T(2) T(3) … T(mid) … T(n-1) T(n)

After compare data & T(mid)

low ←→high low ← →highdata < T(mid)

data > T(mid)

data = T(mid)

mid =(low + high) 2 (ignore decimal fractions.)

Target found



Practice 2

data = T(mid)

idx ← 0, low ← 1, high ← n

Yes

idx ← mid

Looplow high or idx ≠ 0

Loop

mid ← (high + Low)/2

data T(mid)

Yeslow ← mid + 1

No

No

high ← mid 1

○ Integer Variable:idx, low, high, mid

● idx ← 0

low high and≦

idx = 0● mid ←

(low + high)/2

● low ← 1● high ← n

data = T(mid)

● idx ← mid

● low ← mid+2

● high←mid -1

data > T(mid)

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PM Chap 6 - Pseudo-Code