1. CS 240 Computer Programming 1
Flowcharts

2. An informal definition of an algorithm is:
a step-by-step method for solving a problem or doing a task.

3. Algorithm A step-by-step problem-solving procedure
An algorithm is a sequence of unambiguous instructions for solving a problem.
The number of steps of an algorithm will be countable and finite.
It is a sequence of instructions (or set of instructions) to make a program more readable; a process used to answer a question.

4. How to understand the problem?
Define the problem
Analyze the problem
Develop an algorithm/method of solution
Write a computer program corresponding to the algorithm
Test and debug the program
Document the program (how it works and how to use it)

5. Tools Flowcharts Pseudo code
There are two commonly used tools to help to document program logic (the algorithm)
Flowcharts
Pseudo code

6. A flowchart indicates:
Definition
The production flowchart is a visual representation of the sequence of the program. It shows what comes first, second, third, etc
A flowchart indicates:
The steps to be taken in order to solve a problem.
The order or the sequence of these steps.

7. Flowchart Rules
1. Use only one start and one stop per flowchart, --that is, one way in and one way out of the flowchart.
2. The logic flow of the solution is displayed from top to bottom and from left to right.
3. Use the appropriate symbol for each type of operation.
4. Use arrows when moving to another part of the flowchart rather than lines.
5. Do not leave dead-ends--that is, a part of a question unanswered.

8. Symbols Description Symbol TERMINAL - To start or end a flowchart
TERMINAL - To start or end a flowchart
INPUT / OUTPUT - Used with Read, Input, Print and other I/O commands.
PROCESSING - Used for operations done inside the computer. Such as calculations, storing and moving of data.
DECISION - Used to ask a question in programming. Questions are Yes/No format (Used with the If Statement).
DIRECTION FLOW - Used to connect symbols and to represent the direction of flow. Lines should not cross each other. Arrowheads should be placed at the end close to the symbol.
Connector - or joining of two parts of program

9. 1.Simple sequential Flowchart
Example 1
Construct a flow chart that prints "Hello, World"?

10. 1.Simple sequential Flowchart
Algorithm
Step 1- Start
Step 2- Print "Hello, World"
Step 3- Stop

11. 1.Simple sequential Flowchart
Start
Print
“Hello, World”
Stop

12. 1.Simple sequential Flowchart
Example 2
Construct a flow chart that finds the sum of two numbers.

13. 1.Simple sequential Flowchart
Variables
Algorithm
A: First Number
Step 1- Start
Step 2- Read A
B: Second Number
Step 3- Read B
C: Sum (A+B)
Step 4- Calculate C = A+B
Step 5- Print C
Step 6- Stop

14. 1.Simple sequential Flowchart
Start
Read A
Read B
C= A+B
Print C
Stop
Flowchart

15. 1.Simple sequential Flowchart
Example 3
Construct a flow chart that finds the sum, average and product of three numbers.

16. 1.Simple sequential Flowchart
Variables
Algorithm
X: First Number
Step 1- Start
Y: Second Number
Step 2- Read X, Y, Z
Step 3- Calculate S = X+Y+Z
Z: Third Number
Step 4- Calculate A = S/3
S: Sum (X+Y+Z)
Step 5- Calculate P = X*Y*Z
A: Average (S/3)
Step 6- Print S, A, P
P: Product (X*Y*Z)
Step 7- Stop

17. 1.Simple sequential Flowchart
Start
Read X,Y,Z
S= X+Y+Z
A=S/3
P=X*Y*Z
Print S,A,P
Stop

18. 1.Simple sequential Flowchart
Example 4
Construct a flow chart that finds the difference and the division of two numbers and display the result

19. 1.Simple sequential Flowchart
Variables
Algorithm
N1 : First Number
Step 1- Start
N2 : Second Number
Step 2- Read N1, N2
Step 3- Calculate D = N1-N2
D: Difference
Step 4- Calculate V = N1/N2
V: Division
Step 5- Print D,V
Step 6- Stop

20. 1.Simple sequential Flowchart
Start
Read N1, N2
D= N1 –N2
V=N1/N2
Print D,V
Stop

21. 1.Simple sequential Flowchart
Example 5
Exercise
Construct a flow chart that finds the circle area and circumference of a circle where R (radius) is given

22. 1.Simple sequential Flowchart
Variables
Algorithm
R : Radius
Step 1- Start
PI: PI = 3.14
Step 2- Read R
Step 3- Calculate A = PI*(R)2
A: Area
Step 4- Calculate C = 2*PI*R
C: Circumference
Step 5- Print R, A, C
Step 6- Stop

23. Construct a flow chart for the following function
2. Branched Flowcharts
Example 1
Construct a flow chart for the following function
F(x) = {
X X>=0
-X X<0

24. 2. Branched Flowcharts Variables Algorithm X : Number Step 1- Start
F: function of X
Step 2- Read X
Step 3- if X >=0 then F =X
Step 4- if X <0 then F =-X
Step 5- Print F
Step 6- Stop

25. 2. Branched Flowcharts Flowchart Start Read X YES NO X>=0 F=X F=-X
Print F
Stop
F=-X
F=X
X>=0
YES NO
Flowchart

26. Trace the following flowchart and write the output of it.
2. Branched Flowcharts
Example 2
Trace the following flowchart and write the output of it.
1. When X = 20
2. When X = -10

27. 2. Branched Flowcharts Flowchart Start Read X >0 0> X? =0 W=X+1
Print X,W
Stop
W=2*X-1
W=X+1 X?
>0
0> =0
W=SIN(X)+5
Flowchart

28. 2. Branched Flowcharts Result When X=20 When X=-10 X= 20 X= -10 W= 21

29. Draw a flowchart that shows the traffic light processing
2. Branched Flowcharts
Example 3
Exercise
Draw a flowchart that shows the traffic light processing

30. 2. Branched Flowcharts Variables Algorithm C : Traffic light color
Step 1- Start
Step 2- Read C
Step 3- make a Decision (what is c)
Step 4- if C is RED then Print STOP
Step 5- if C is YELLOW then Print WAIT
Step 6- if C is GREEN then Print PASS
Step 7- Stop

31. Trace the following flowchart and write the output of it.
3. Loop Flowcharts
Example 1
Trace the following flowchart and write the output of it.

32. 3. Loop Flowcharts Flowchart Start N=1 Print N F While N<=7 Stop T
N=N+3
While N<=7 F T
N=1
Print N

33. 3. Loop Flowcharts
Result N
Loop 1 4 2 7 3

34. Trace the following flowchart and write the output of it.
3. Loop Flowcharts
Example 2
Trace the following flowchart and write the output of it.

35. 3. Loop Flowcharts Flowchart Start i=0 Sum=0 F While i<10
Print avg
Stop
Sum= X + Sum
Increment i
avg=Sum/10
While i<10 F T
i=0
Sum=0
Read X
Flowchart

36. 3. Loop Flowcharts Result Avg =50/10 =5 Loop Read X Sum i 1 3 2 4 7 818 5 25 6 30 33 41 9 45 50
Avg =50/10 =5