MODULE 1

(LABORATORY)

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Algorithms

• Algorithm: the step-by-step sequence of

instructions that describe how the data is to be
processed to produce the desired output
• Programming = the translation of the selected
algorithm into a language the computer can use

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Algorithms (continued)

• Pseudocode: English-like phrases used to

describe the algorithm
• Formula: description of a mathematical
equation
• Flowchart: diagram showing the flow of
instructions in an algorithm
– Flowcharts use special symbols

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 Expressing Algorithms
Algorithms can be expressed in many kinds of notation,
including:
• Natural Languages
• Pseudocode
• Flowcharts
• Programming Languages
Pseudocode
• A program design technique that uses English words.
• Has no formal syntactical rules.
• Pseudo means false, thus pseudocode means false code. It looks like
(imitates) real code but it is NOT real code.
• Pseudocode cannot be compiled nor executed, and there are no real
formatting or syntax rules.
• Pseudocode should not include keywords in any specific computer
languages.
• The benefit of pseudocode is that it enables the programmer to concentrate
on the algorithms without worrying about all the syntactic details of a
particular programming language.
 How do I write Pseudocode?
• First you may want to make a list of the main tasks that must
be accomplished on a piece of scratch paper.

• Then, focus on each of those tasks. Generally, you should try

to break each main task down into very small tasks that can
each be explained with a short phrase.

• There may eventually be a one-to-one correlation between

the lines of pseudocode and the lines of the code that you
write after you have finished pseudocoding.
• It is not necessary in pseudocode to mention the need to
declare variables. It is wise however to show the initialization
of variables.

• All statements showing "dependency" are to be indented.

These include while, do, for, if, switch.

Some Keywords That Should be Used

For looping and selection, the keywords that are to be used
include:
Do While...EndDo Call ... with (parameters)
Do Until...Enddo Call
Case...EndCase Return
If...Endif When
As verbs, use the words:

Generate, Compute, Process

Set, Reset, Increment, Compute, Test
Calculate, Add, Sum, Multiply, ...
Print, Display, Input, Output, Edit
Pseudocode Examples
Original Program Specification:

Write a program that obtains two integer numbers from

the user. It will print out the sum of those numbers.

Pseudocode:

Prompt the user to enter the first integer

Prompt the user to enter a second integer
Compute the sum of the two user inputs
Display an output prompt that explains the answer as the
sum
Display the result
Original Program Specification:

Write a program that will display if the entered student’s

grade is passed of failed. Passing grade is 70.

Pseudocode:

Prompt the user to enter a student grade

If student's grade is greater than or equal to 70
Print "passed"
else
Print "failed"
Original Program Specification:

Write a program that will allow the student to input the grade
on his 5 subjects and will compute for his average grade.

Original Program Specification:

Set total to zero

Set grade counter to one
While grade counter is less than or equal to 5
Input the next grade
Add the grade into the total
Set the class average to the total divided by 5
Print the class average.
Pseudocode example : If then Else

If age > 17
Display a message indicating you can vote.
Else
Display a message indicating you can't vote.
Endif

Pseudocode example : Case

Case of age
0 to 17 Display "You can't vote."
18 to 64 Display "Your in your working years."
65 + Display "You should be retired."
Endcase
Pseudocode example : While loop

count assigned zero

While count < 5
Display "I love computers!"
Increment count
Endwhile

Pseudocode example : For loop

For x starts at 0, x < 5, increment x

Display "Are we having fun?"
Endfor
Pseudocode example : Do While loop

count assigned five

Do
Display "Blast off is soon!"
Decrement count
While count > zero

Pseudocode example : Repeat Until loop

count assigned five

Repeat
Display "Blast off is soon!"
Decrement count
Until count < one
Pseudocode example : Function with no parameter
passing

Function clear monitor

Pass In: nothing
Direct the operating system to clear the monitor
Pass Out: nothing
Endfunction
Pseudocode example : Function with parameter passing

Function delay program so you can see the monitor

Pass In: integer representing tenths of a second
Using the operating system delay the program
Pass Out: nothing
Endfunction
Pseudocode of : Function main calling the clear monitor
function

Function main
Pass In: nothing
Doing some lines of code
Call: clear monitor
Doing some lines of code
Pass Out: value zero to the operating system
Endfunction
Flowcharts Symbols
Flowcharts Symbols (continued)
Flowcharts (continued)

Flowchart for calculating the

average of three numbers.

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 Guidelines for Drawing a Flowchart

• In drawing a proper flowchart, all necessary requirements

should be listed out in logical order.

• The flowchart should be clear, neat and easy to follow. There

should not be any room for ambiguity in understanding the
flowchart.

• The usual direction of the flow of a procedure or system is

from left to right or top to bottom.
• Only one flow line should come out from a process
symbol.

• Only one flow line should enter a decision symbol, but two or
three flow lines, one for each possible answer, should leave the
decision symbol.
• If the flowchart becomes complex, it is better to use
connector symbols to reduce the number of flow lines.
Avoid the intersection of flow lines if you want to make it
more effective and better way of communication.

• Ensure that the flowchart has a logical start and finish.

• It is useful to test the validity of the flowchart by passing

through it with a simple test data.
Advantages of using flowcharts

The benefits of flowcharts are as follows:

• Communication: Flowcharts are better way of communicating

the logic of a system to all concerned.

• Effective analysis: With the help of flowchart, problem can be

analyzed in more effective way.

• Proper documentation: Program flowcharts serve as a good

program documentation, which is needed for various purposes.
• Efficient Coding: The flowcharts act as a guide or blueprint during the systems
analysis and program development phase.

• Proper Debugging: The flowchart helps in debugging process.

• Efficient Program Maintenance: The maintenance of operating

program becomes easy with the help of flowchart. It helps the
programmer to put efforts more efficiently on that part
Limitations of using flowcharts
• Complex logic: Sometimes, the program logic is quite
complicated. In that case, flowchart becomes complex and
clumsy.

• Alterations and Modifications: If alterations are required the

flowchart may require re-drawing completely.

• Reproduction: As the flowchart symbols cannot be typed,

reproduction of flowchart becomes a problem.
Flowcharting Examples

Example 1

Draw a flowchart to find

the sum of first 50
natural numbers.
Example 2
Draw a flowchart
to find the largest
of three numbers
A,B, and C.
Example 3
Draw a flowchart for
computing factorial N (N!)
Where N! = 1 ´ 2 ´ 3 ´ …… N
.
Problem Solving Process

Input Process Output

Example Problem #1

Calculate and display the price of a number

of apples if the quantity in kg and price per kg
are given.

Input Process Output

• Quantity Price = Quantity * Price_per_kg
• Price_per_kg Price
Pseudocode

1. Start
2. Read quantity
3. Read price_per_kg
4. price  quantity *
price_per_kg
5. Print price
6. End
Flowchart: Calculate Price of Apples
Start

Input
Quantity
Input
Price_per_kg

Price = Quantity * Price_per_kg

Output
Price

End
Source Code
#include<iostream> Pre-processor
using namespace std;
int main()
Main function
{
int price = 0, quantity = 0; Start
float price_per_kg = 0; Variable declarations
cout << "Enter quantity of an apple : " ;
cin >> quantity; Input
cout << "Enter price of an apple per kilogram : " ;
cin >> price_per_kg; Input
price = quantity * price_per_kg; computations
cout << "The price of an apple in kilogram is " << price << "\n";
system ("pause");
return 0;
} Output
Stop
Example #2

A car park has the following charges:

The 1st hour costs Php 5.00. The
subsequent hour cost Php 2.00 per hour.
Write an algorithm based on a vehicle’s
entry and exit time.

Input Process Output

• Entry_time Charge
????
• Exit_time
Flowchart: Calculate Car Park Charge
Start

Input Entry_time
Input Exit_time

Period = Exit_time – Entry_time

Charge = 5 If Charge = (Period -1) * 2

No Period > 1 Yes

Output
Charge

End
Laboratory
Activities
Problem #1:

Given three numbers A,B,C. Draw

a flowchart to compute and print
out the sum, the average, and the
product of these values.
Problem #2:

Create a flowchart from the

given Algorithm below.
Step 1: Read in the values of X and Y.
Step 2: Subtract Y from X.
Step 3. If the difference between the X and Y is negative, compute
R=X+Y; if zero, compute R=2x+2y; and if positive, compute
R=X*Y.
Copy And Paste In Your Browser For
Additional Learnings

Introduction to Algorithms and flowchart in C++

Programming

https://www.youtube.com/watch?v=W8-iX15matg
End of Module 1