spring 2019 cse 112 (computer fundamentals topic
TRANSCRIPT
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CSE 112 (Computer Fundamentals
Course Teacher:
Professor Dr. Md. Ismail Jabiullah
Professor
Department of Computer Science and Engineering
Daffodil International University
Topic: Flowchart and Pseudocode
Spring 2019
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References
2
Computer Fundamentals by Pradeep K. Sinha,
6th Edition. [Chapter 11]
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Algorithm
§ Refers to the logic of a program and a step-by-step
description of how to arrive at the solution of a givenproblem
§ In order to qualify as an algorithm, a sequence of
instructions must have following characteristics:
§ Each and every instruction should be precise andunambiguous
§ Each instruction should be such that it can be performed ina finite time
§ One or more instructions should not be repeated infinitely.This ensures that the algorithm will ultimately terminate
§ After performing the instructions, that is after the algorithmterminates, the desired results must be obtained
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Sample Algorithm (Example 1)
There are 50 students in a class who appeared in theirfinal examination. Their mark sheets have been given toyou.
The division column of the mark sheet contains thedivision (FIRST, SECOND, THIRD or FAIL) obtained by thestudent.
Write an algorithm to calculate and print the total numberof students who passed in FIRST division.
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CC
Sample Algorithm (Example 1)
(contd…)Step 1: Initialize Total_First_Division and
Total_Marksheets_Checked to zero.
Step 2: Take the mark sheet of the next student.
Step 3: Check the division column of the mark sheet to see if it is
FIRST, if no, go to Step 5.
Step 4: Add 1 to Total_First_Division.
Step 5: Add 1 to Total_Marksheets_Checked.
Step 6: Is Total_Marksheets_Checked = 50, if no, go to Step 2.
Step 7: Print Total_First_Division.
Step 8: Stop.
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Sample Algorithm (Example 2)
There are 100 employees in an organization. The organization
wants to distribute annual bonus to the employees based on their
performance. The performance of the employees is recorded in
their annual appraisal forms.
Every employee’s appraisal form contains his/her basic salary and
the grade for his/her performance during the year. The grade is of
three categories – ‘A’ for outstanding performance, ‘B’ for good
performance, and ‘C’ for average performance.
It has been decided that the bonus of an employee will be 100% of
the basic salary for outstanding performance, 70% of the basic
salary for good performance, 40% of the basic salary for average
performance, and zero for all other cases.
Write an algorithm to calculate and print the total bonus amount to
be distributed by the organization.
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Sample Algorithm (Example 2)
(contd…)Step 1: Initialize Total_Bonus and Total_Employees_Checked to zero.
Step 2: Initialize Bonus and Basic_Salary to zero.
Step 3: Take the appraisal form of the next employee.
Step 4: Read the employee’s Basic_Salary and Grade.
Step 5: If Grade = A, then Bonus = Basic_Salary. Go to Step 8.
Step 6: If Grade = B, then Bonus = Basic_Salary x 0.7. Go to Step 8.
Step 7: If Grade = C, then Bonus = Basic_Salary x 0.4.
Step 8: Add Bonus to Total_Bonus.
Step 9: Add 1 to Total_Employees_Checked.
Step 10: If Total_Employees_Checked < 100, then go to Step 2.
Step 11: Print Total_Bonus.
Step 12: Stop.
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Representation of Algorithms
§ As programs
§ As flowcharts
§ As pseudocodes
When an algorithm is represented in the form of aprogramming language, it becomes a program
Thus, any program is an algorithm, although thereverse is not true
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Flowchart
§ Flowchart is a pictorial representation of an algorithm
§ Uses symbols (boxes of different shapes) that have
standardized meanings to denote different types ofinstructions
§ Actual instructions are written within the boxes
§ Boxes are connected by solid lines having arrow marks to
indicate the exact sequence in which the instructions areto be executed
§ Process of drawing a flowchart for an algorithm is called
flowcharting
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Basic Flowchart Symbols
Terminal
Decision
Input/Output
Flow lines
Processing
Connectors
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Examples of Decision Symbol
No A < B Compare
A & B
A > BIs I = 10?
YesA = B
(a) A two-way branch decision. (b) A three-way branch decision.
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Examples of Decision Symbol
(contd…)
I = ?
= 0 = 1 = Other= 2 = 3 = 4 = 5
(c) A multiple-way branch decision.
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Sample Flowchart (Example 3)
A student appears in an examination, which consists oftotal 10 subjects, each subject having maximum marksof 100.
The roll number of the student, his/her name, and themarks obtained by him/her in various subjects aresupplied as input data.
Such a collection of related data items, which is treatedas a unit is known as a record.
Draw a flowchart for the algorithm to calculate thepercentage marks obtained by the student in thisexamination and then to print it along with his/her rollnumber and name.
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Sample Flowchart (Example 3)
Start (contd…)
Read input data
Add marks of all
subjects giving Total
Percentage = Total / 10
Write output data
Stop
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Sample Flowchart (Example 4)
50 students of a class appear in the examination ofExample 3.
Draw a flowchart for the algorithm to calculate and printthe percentage marks obtained by each student alongwith his/her roll number and name.
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CCoommppuutteerr FFuunnddaammeennttaallss:: PPrraaddeeeepp KK.. SSiinnhhaa && PPrriittii SSiinnhhaa
Sample Flowchart (Example 4)
Start (contd…)
Read input data
Flowchart for the solution
of Example 4 with an
infinite (endless) process
loop.
Add marks of all
subjects giving Total
Percentage = Total / 10
Write output data
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C
Sample Flowchart (Example 4)
Start (contd…)
Count = 0
Read input data
Add marks of all subjects giving Total
Percentage = Total/10
Write output data
Flowchart for the solution
of Example 4.Add 1 to Count
NoIs Count = 50?
Yes
Stop
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Co
Sample Flowchart (Example 4)
Start (contd…)
Read input data
YesIs Rollno = 0000000?
Generalized flowchartNo for the solution of
Example 4 using theconcept of trailerrecord. Here theprocess loop is
Add marks of all subjectsStop
giving Total
terminated by detecting
a special non-datarecord.
Percentage = Total / 10
Write output data
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Sample Flowchart (Example 5)
For the examination of Example 3, we want to make alist of only those students who have passed (obtained30% or more marks) in the examination.
In the end, we also want to print out the total number ofstudents who have passed.
Assuming that the input data of all the students isterminated by a trailer record, which has sentinel valueof 9999999 for Rollno, draw a flowchart for thealgorithm to do this.
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Sample Flowchart (Example 5)
Start (contd…)
Count = 0
Read input data
Yes
No
Is Rollno = 9999999?
Write CountNo
Add marks of all subjects giving Total Stop
Percentage = Total/10
Is Percentage = > 30?
Yes
Write output data
Add 1 to Count
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C
Sample Flowchart (Example 6)
Suppose the input data of each student for the examinationof Example 3 also contains information regarding the sex ofthe candidate in the field named Sexcode having values M(for male) or F (for female).
We want to make a list of only those female students whohave passed in second division (obtained 45% or more butless than 60% marks).
In the end, we also want to print out the total number ofsuch students.
Assuming that the input data of all the students isterminated by a trailer record, which has a sentinel value of Zfor Sexcode,
Draw a flowchart for the algorithm to do this.
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Sample Flowchart (Example 6)
Start
Count = 0
1
1
Read input data
Yes 2Is Sexcode = Z?
No
No Is Sexcode = F?
Yes
Add marks of all subjects giving Total
Percentage = Total / 10
3
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Sample Flowchart (Example 6)
(contd…)3
No
No
1
1
Is Percentage = > 45?
Yes2
Is Percentage < 60?
Write CountYes
Write output dataStop
Add 1 to Count
1
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Pseudocode
§ A program planning tool where program logic is written in
an ordinary natural language using a structure thatresembles computer instructions
§ “ Pseudo” means imitation or false and “ Code” refers to
the instructions written in a programming language.Hence, pseudocode is an imitation of actual computerinstructions
§ Because it emphasizes the design of the program,
pseudocode is also called Program Design Language(PDL)
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C
Basic Logic (Control) Structures
Any program logic can be expressed by using onlyfollowing three simple logic structures:
1. Sequence logic,
2. Selection logic, and
3. Iteration (or looping) logic
Programs structured by using only these three logicstructures are called structured programs, and thetechnique of writing such programs is known asstructured programming
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C
Sequence Logic
It is used for performing instructions one after anotherin sequence.
Process 1
Process 1Process 2
Process 2
(a) Flowchart (b) Pseudocode
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Selection Logic
• Also known as decision logic, it is used for makingdecisions
• Three popularly used selection logic structures are
1. IF…THEN…ELSE
2. IF…THEN
3. CASE
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C
Selection Logic (IF…THEN…ELSE Structure)
IF ConditionYes NoIF (condition)
THEN Process 1
THEN ELSE
Process 2
ELSE Process 2
Process 1ENDIF
(a) Flowchart (b) Pseudocode
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C
Selection Logic (IF…THEN Structure)
Yes NoIF (condition)
IF Condition
THEN
Process 1
THEN Process 1
ENDIF
(a) Flowchart (b) Pseudocode
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C
Selection Logic (CASE Structure)
Yes
Yes
Type 1 Process 1
Process 2
No
Type 2 CASE Type
Case Type 1: Process 1No
Case Type 2: Process 2
YesType n
No
Process n
Case Type n: Process n
ENDCASE
(a) Flowchart
(b) Pseudocode
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C
Iteration (or Looping) Logic
§ Used to produce loops in program logic when one or
more instructions may be executed several timesdepending on some conditions
§ Two popularly used iteration logic structures are
1. DO…WHILE
2. REPEAT…UNTIL
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C
Iteration (or Looping) Logic(DO…WHILE Structure)
FalseCondition?
True
Process 1 DO WHILE Condition
Process 1
Block
Process n
ENDDOProcess n
(a) Flowchart (b) Pseudocode
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C
Iteration (or Looping) Logic(REPEAT…UNTIL Structure)
Process 1
REPEAT
Process 1Process n
Process nFalse
Condition? UNTIL Condition
True
(b) Pseudocode(a) Flowchart
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Sample Pseudocode (for Example 6)
Set Count to zero
Read first student record
DO WHILE Sexcode is not equal to Z
IF Sexcode = F THEN
Calculate Percentage
IF Percentage = > 45 THEN
IF Percentage < 60 THEN
Write output data
Add 1 to CountENDIF
ENDIF
ENDIFRead next student record
ENDDO
Write CountStop
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The End