Problem Solving and Programming

20CST11 – Problem Solving and
Programming
By
Mr.S.Selvaraj
Asst. Professor(SRG) / CSE
Kongu Engineering College
Unit I – Introduction to Computer
and Problem Solving

20CST11 – Problem Solving and Programming
1/7/2021 Introduction to Computers 2
Syllabus

Contents
1. Introduction to Computer
2. Functionalities of Computer
3. Characteristics of Computer
4. Cons of Computers
5. Uses of Computers
6. Types of Computers
7. Generation of Computers
8. Functional Units of Computer
9. Hardware and Software
1/7/2021 3Introduction to Computers

1. Introduction to Computers
• Computers are everywhere:
– at workplace
– at school
– at home
• In the workplace, employees use computer to
create correspondence such as
– e-mail messages, memos, and letters
– manage calendars
– calculate payroll
– track inventory and generate invoices

1. Introduction to Computers
• At school,
– teachers use computer to assist with classroom instruction.
– Students use computers to complete assignments and research.
• At home, People also spend hours of leisure time using a computer.
– play games
– communicate with friend and relatives online and using e-mail
– purchase goods online
– converse in chat rooms
– listen to music or radio broadcasts
– watch or create videos and movies
– read books and magazines
– share stories
– research genealogy
– retouch photos and plan vacations.

• A computer is an electronic device.
• It operating under the control of instructions stored in its
own memory.
• It can accept data (input)
• It process the data according to specified rules (process)
• It produce results (output) and
• It store the results (storage) for future use.
• Generally, the term is used to describe a collection of
electric, electronic, and mechanical components known
as hardware.

• If we look at it in a very broad sense, any digital
computer carries out the following five functions:
– Step 1: Takes data as input.
– Step 2: Stores the data/instructions in its memory and
uses them as required.
– Step 3: Processes the data and converts it into useful
information.
– Step 4: Generates the output.
– Step 5: Controls all the above four steps.

3. Characteristics of Computer
• Speed
• Accuracy
• Diligence
• Versatility
• Storage capacity
• Reliability
• Automation
• Reduction in Paper work and Cost

Speed
• Computers work at an incredible speed.
• A powerful computer is capable of performing about 3-
4 million simple instructions per second.
• It is capable of performing calculation of very large
amount of data.
• The computer has units of speed in microsecond,
nanosecond, and even the picosecond.
• It can perform millions of calculations in a few seconds
as compared to man who will spend many months to
perform the same task.

Accuracy
• In addition to being fast, computers are also accurate.
• Computers perform all jobs with 100% accuracy
provided that the input is correct.
• The calculations are 100% error free.
• Errors that may occur can almost always be attributed
to human error (inaccurate data, poorly designed
system or faulty instructions/programs written by the
programmer)

Diligence
• Unlike human beings, computers are highly consistent.
• They do not suffer from human traits of boredom and
tiredness resulting in lack of concentration.
• Computers, therefore, are better than human beings in
performing voluminous and repetitive jobs.
• It can work continuously without any error and boredom.
• It can perform repeated tasks with the same speed and
accuracy.

Versatility
• Computers are versatile machines and are capable of performing
any task as long as it can be broken down into a series of logical
steps.
• A computer is very flexible in performing the jobs to be done.
• Computer can be used to solve the problems related to various
fields.
• At one instance, it may be solving a complex scientific problem and
the very next moment it may be playing a card game.
• The presence of computers can be seen in almost every sphere –
Railway/Air reservation, Banks, Hotels, Weather forecasting and
many more.

Storage Capacity
• Today’s computers can store large volumes of data.
• A piece of information once recorded (or stored) in the
computer, can never be forgotten and can be retrieved
almost instantaneously.
• Memory is a very important characteristic of computers.
• A computer has much more storage capacity than human
beings.
• It can store any type of data such as images, videos, text,
audio, etc.

4. Cons of Computer
• No I.Q (Intelligence Quotient)
– A computer is a machine that has no intelligence to perform any task.
– Each instruction has to be given to the computer.
– A computer cannot take any decision on its own.
• No Feeling
– Computers have no feelings or emotions.
– It cannot make judgment based on feeling, taste, experience, and
knowledge unlike humans.
• Dependency
– It functions as per the user’s instruction, thus it is fully dependent on
humans.
• Environment
– The operating environment of the computer should be dust free and
suitable.

5. Uses of Computer
• Scientific, Engineering and Research
• Business
• Marketing
• Medicine
• Information Technology
• Education
• Banking and Insurance
• Healthcare
• Engineering Design
• Military
• Communication
• Government

6. Types of Computer
Type Specifications
PC (Personal
Computer)
It is a single user computer system having moderately powerful
microprocessor.
Workstation It is also a single user computer system, similar to personal
computer however has a more powerful microprocessor
Mini Computer It is a multi-user computer system, capable of supporting hundreds
of users simultaneously.
Main Frame It is a multi-user computer system, capable of supporting hundreds
of users simultaneously. Software technology is different from
minicomputer.
Supercomputer It is an extremely fast computer, which can execute hundreds of
millions of instructions per second. For example, weather
forecasting, scientific simulations, (animated) graphics, fluid
dynamic calculations, nuclear energy research, electronic design,
and analysis of geological data (e.g. in petrochemical prospecting).

7. Generation of Computer
Generation Description
First
Generation
i. The period of first generation: 1946-1959.
ii. Vacuum tube based.
Second
Generation
i. The period of second generation: 1959-1965.
ii. Transistor based.
Third
Generation
i. The period of third generation: 1965-1971.
ii. Integrated Circuit based.
Fourth
Generation
i. The period of fourth generation: 1971-1980.
ii. VLSI microprocessor based.
Fifth
Generation
i. The period of fifth generation: 1980-
onwards.
ii. ULSI microprocessor based.

Operation Description
Take Input  The process of entering data and instructions into the computer
system
Store Data  Saving data and instructions so that they are available for processing
as and when required.
Processing
Data
 Performing arithmetic, and logical operations on data in order to
convert them into useful information.
Output
Information
 The process of producing useful information or results for the user,
such as a printed report or visual display.
Control the
workflow
 Directs the manner and sequence in which all of the above
operations are performed.

• Hardware
– Hardware represents the physical
and tangible components of a
computer.
– i.e. the components that can be seen
and touched.
• Examples of Hardware are the
following:
– Input devices: keyboard, mouse, etc.
– Output devices: printer, monitor, etc.
– Secondary storage devices: Hard disk,
CD, DVD, etc.
– Internal components: CPU,
motherboard, RAM, etc

• Software
– Software is a set of programs, which is designed to
perform a well-defined function.
– A program is a sequence of instructions written to solve a
particular problem.
• There are two types of software:
– System Software
– Application Software

System Software
• The system software is a collection of programs designed to
operate, control, and extend the processing capabilities of
the computer itself.
• System software is generally prepared by the computer
manufacturers.
• These software products comprise of programs written in
low-level languages, which interact with the hardware at a
very basic level.
• System software serves as the interface between the
hardware and the end users.
• Some examples of system software are
– Operating System
– Compilers
– Interpreter
– Assemblers, etc.

Application Software
• Application software products are designed to satisfy a particular
need of a particular environment.
• All software applications prepared in the computer lab can come
under the category of Application software.
• Application software may consist of a single program, such as
Microsoft's notepad for writing and editing a simple text.
• It may also consist of a collection of programs, often called a
software package, which work together to accomplish a task, such
as a spreadsheet package. (MS Office)
• Examples of Application software are the following:
– Payroll Software
– Student Record Software
– Inventory Management Software
– Income Tax Software
– Railways Reservation Software
– Microsoft Office Suite Software

Thank you

Inside of Computer
By
Mr.S.Selvaraj
Asst. Professor(SRG) / CSE

Contents
• Hardware Component of Computer
• Motherboard Structure
• Interfaces
– Input/Output Interface
– Processor Interface
– Main Memory Interface
– Secondary Memory Interface
– Other Interfaces
Introduction to Problem Solving Techniques1/7/2021 26

1. Hardware Components of Computer

1/7/2021 Introduction to Problem Solving Techniques 28

Motherboard Structure

RAM

ROM

Hard Disk

Functional Units of Computer

Basic Organization of Computer

Thank you

Introduction to Problem Solving
Techniques
By
Mr.S.Selvaraj
Asst. Professor (SRG) / CSE

Contents
• Introduction
• Steps involved in Problem Solving
• Problem Solving Techniques
– Algorithm
– Flowchart
– Pseudo Code
– Program

1. Introduction
• A computer is a very powerful and versatile machine
capable of performing a multitude of different tasks,
yet it has no intelligence or thinking power.
• The intelligence Quotient (I.Q) of a computer is zero.
• This places responsibility on the user to instruct the
computer in a correct and precise manner, so that the
machine is able to perform the required job in a proper
way.
• A wrong or ambiguous instruction may sometimes
prove disastrous.

1. Introduction
• In order to instruct a computer correctly, the user must
have clear understanding of the problem to be solved.
• A part from this the user should be able to develop a
method, in the form of series of sequential steps, to
solve it.
• Once the problem is well-defined and a method of
solving it is developed, then instructing the computer
to solve the problem becomes relatively easier task.
• Thus, before attempt to write a computer program to
solve a given problem.
– It is necessary to formulate or define the problem in a
precise manner.
– Once the problem is defined, the steps required to solve it,
must be stated clearly in the required order.

2. Steps involved in Problem Solving
• A computer cannot solve a problem on its own.
• One has to provide step by step solutions of the problem to
the computer.
• In fact, the task of problem solving is not that of the
computer. It is the programmer who has to write down the
solution to the problem in terms of simple operations which
the computer can understand and execute.
• In order to solve a problem by the computer, one has to pass
though certain stages or steps.
• They are
– 1.Understanding the problem
– 2. Analyzing the problem
– 3.Developing the solution
– 4.Coding and implementation.

2.Steps involved in Problem Solving
• 1.Understanding the problem:
– Here we try to understand the problem to be solved in
totally.
– Before with the next stage or step, we should be
absolutely sure about the objectives of the given problem.
• 2.Analyzing the problem:
– After understanding thoroughly the problem to be solved,
we look different ways of solving the problem and evaluate
each of these methods.
– The idea here is to search an appropriate solution to the
problem under consideration.
– The end result of this stage is a broad overview of the
sequence of operations that are to be carries out to solve
the given problem.

2.Steps involved in Problem Solving
• 3. Developing the solution:
– Here the overview of the sequence of operations that
was the result of analysis stage is expanded to form a
detailed step by step solution to the problem under
consideration.
• 4. Coding and implementation:
– The last stage of the problem solving is the conversion
of the detailed sequence of operations in to a
language that the computer can understand.
– Here each step is converted to its equivalent
instruction or instructions in the computer language
that has been chosen for the implantation.

3. Problem Solving Techniques
• Algorithm
• Flowchart
• Pseudo Code
• Program

3.1 Algorithm
Introduction to Problem Solving Techniques
• A set of sequential steps usually written in Ordinary
Language to solve a given problem is called Algorithm.
• An algorithm can be defined as “a complete,
unambiguous, finite number of logical steps for solving
a specific problem”
• It may be possible to solve to problem in more than
one ways, resulting in more than one algorithm.
• The choice of various algorithms depends on the
factors like reliability, accuracy and easy to modify.
• The most important factor in the choice of algorithm is
the time requirement to execute it, after writing code
in High-level language with the help of a computer.
• The algorithm which will need the least time when
executed is considered the best.
1/7/2021 44

3.1 Steps in Algorithm Development
• Step1. Identification of input:
– For an algorithm, there are quantities to be supplied
called input and these are fed externally.
– The input is to be indentified first for any specified
problem.
• Step2: Identification of output:
– From an algorithm, at least one quantity is produced,
called output for any specified problem.
• Step3 : Identification the processing operations :
– All the calculations to be performed in order to lead to
output from the input are to be identified in an
orderly manner.
1/7/2021 45

3.1 Steps in Algorithm Development
• Step4 : Processing Definiteness :
– The instructions composing the algorithm must be
clear and there should not be any ambiguity in them.
• Step5 : Processing Finiteness :
– If we go through the algorithm, then for all cases, the
algorithm should terminate after a finite number of
steps.
• Step6 : Possessing Effectiveness :
– The instructions in the algorithm must be sufficiently
basic and in practice they can be carries out easily.

Example for Algorithm
• Example1:
• Suppose we want to find the average of three
numbers, the algorithm is as follows:
– Step 1: Start the program
– Step 2: Read the numbers a, b, c
– Step 3: Compute the sum of a, b and c
– Step 4: Divide the sum by 3
– Step 5: Store the result in variable d
– Step 6: Print the value of d
– Step 7: End of the program

3.2 Flowchart
• A flow chart is a step by step diagrammatic
representation of the logic paths to solve a given
problem.
• Or
• A flowchart is visual or graphical representation of an
algorithm.
• The flowcharts are pictorial representation of the
methods to be used to solve a given problem and help
a great deal to analyze the problem and plan its
solution in a systematic and orderly manner.
• A flowchart when translated into a proper computer
language, results in a complete program.

Advantages of Flowcharts
• The flowchart shows the logic of a problem displayed
in pictorial fashion which felicitates easier checking of
an algorithm.
• The Flowchart is good means of communication to
other users. It is also a compact means of recording an
algorithm solution to a problem.
• The flowchart allows the problem solver to break the
problem into parts. These parts can be connected to
make master chart.
• The flowchart is a permanent record of the solution
which can be consulted at a later time.

Difference b/w Algorithm and Flowcharts
Algorithm Flowcharts
A method of representing the step-
by-step logical procedure for solving
a problem
Flowchart is diagrammatic
representation of an algorithm. It is
constructed using different types of
boxes and symbols.
It contains step-by-step English
descriptions, each step representing
a particular operation leading to
solution of problem
The flowchart employs a series of
blocks and arrows, each of which
represents a particular step in an
algorithm
These are particularly useful for
small problems
These are useful for detailed
representations of complicated
programs
For complex programs, algorithms
prove to be Inadequate
For complex programs, Flowcharts
prove to be adequate
1/7/2021 50

Symbols used in Flowcharts
Symbol Name Symbol Description
Oval Rectangle with rounded sides is used to indicate
either START/STOP of the program. ..
Input and
output
indicators
Parallelograms are used to represent input and
output operations. Statements like INPUT, READ
and PRINT are represented in these
Parallelograms.
Process
Indicators
Rectangle is used to indicate any set of
processing operation such as for storing
arithmetic operations.
Decision Makers The diamond is used for indicating the step of
decision making and therefore known as
decision box. Decision boxes are used to test the
conditions or ask questions and depending upon
the answers, the appropriate actions are taken
by the computer.
1/7/2021 51

Symbols used in Flowcharts
Symbol Name Symbol Description
Flow Lines Flow lines indicate the direction being followed in the
flowchart. In a Flowchart, every line must have an
arrow on it to indicate the direction. The arrows may
be in any direction
On- Page
connectors
Circles are used to join the different parts of a
flowchart and these circles are called on-page
connectors. The uses of these connectors give a neat
shape to the flowcharts. Ina complicated problems, a
flowchart may run in to several pages. The parts of
the flowchart on different pages are to be joined with
each other. The parts to be joined are indicated by
the circle.
Off-page
connectors
This connector represents a break in the path of
flowchart which is too large to fit on a single page. It
is similar to on-page connector. The connector symbol
marks where the algorithm ends on the first page and
where it continues on the second
1/7/2021 52

Example – Flowchart
• Example: Draw a flowchart to perform average of
three numbers.
1/7/2021 53

3.3 Pseudo Code
• The Pseudo code is neither an algorithm nor a
program.
• It is an abstract form of a program.
• It consists of English like statements which
perform the specific operations.
• It is defined for an algorithm.
• It does not use any graphical representation.
• In pseudo code, the program is represented in
terms of words and phrases, but the syntax of
program is not strictly followed.

Example – Pseudo Code
• Example: Write a pseudo code to perform
average of three numbers.
1. Begin
2. Read n1, n2, n3
3. Sum = n1 + n2 + n3
4. Avg = Sum/3
5. Print Avg
6. End

3.4 Program
• Program consists of a series of instructions that a
computer processes to perform, the required operation.
• Or
• A computer program is a collection of instructions that can
be executed by a computer to perform a specific task.
• A computer program is usually written by a computer
programmer in a programming language.
• From the program in its human-readable form of source
code, a compiler or assembler can derive machine code —a
form consisting of instructions that the computer can
directly execute.
• A collection of computer programs, libraries, and related
data are referred to as software.
• Computer programs may be categorized along functional
lines, such as application software and system software.

Example - Program
• Example: Write a C program to perform average of five numbers.

Thank you

Compound Interest (CI)
Five min time .. work out and tell
the answer in chat box

Introduction to Raptor Tool
By
Mr.S.Selvaraj

RAPTOR Tool
• RAPTOR(Rapid Algorithmic Prototyping Tool for
Ordered Reasoning) is a free graphical authoring tool
created by
– Martin C. Carlisle,
– Terry Wilson,
– Jeff Humphries and
– Jason Moore.
• Designed specifically to help students visualize their
algorithms and avoid syntactic baggage.
• Students can create flow-chart for a particular
program.
• Raptor tool will generate code for it in various
programming languages, such as C, C++, Java and so
on.
1/7/2021 Introduction to Raptor Tool 61

Symbols in RAPTOR
• Raptor has 6 types of symbols, each of which
represents a unique kind of instruction.
• They are :
– Assignment
– Call
– Input
– Output
– Selection and
– Loop

RAPTOR Program Structure
• A RAPTOR program consists of connected
symbols that represent actions to be executed.
• The arrows that connect the symbols determine
the order in which the actions are performed.
• The execution of a RAPTOR program begins at the
Start symbol and goes along the arrows to
execute the program.
• The program stops executing when the End
symbol is reached.

RAPTOR Tool

Sample RAPTOR Flowchart

Sample RAPTOR Program
• With the help of Generate option, the generated C++
code for the above flow chart is:

C++ code
generated from
RAPTOR tool
• // CPP program for illustrating RAPTOR
• #include <iostream>
• #include <string>
• using namespace std;
• int main()
• {
• string raptor_prompt_variable_zzyz;
• float m;
• raptor_prompt_variable_zzyz ="enter the marks";
• cout << raptor_prompt_variable_zzyz << endl;
• cin >> m;
• if (m>=90)
• {
• cout << "The grade is A" << endl; }
• else
• {
• if (m>=80)
• {
• cout << "The grade is B" << endl; }
• else
• {
• if (m>=60)
• {
• cout << "The grade is C" << endl; }
• else
• {
• cout << "The grade is D" << endl; }
• }
• }
• return 0;
• }

Thank you
Introduction to Raptor Tool1/7/2021 68

Structuring the logic: Sequential
By
Mr.S.Selvaraj

Sequencing
• Sequencing is represented by
– rectangular boxes for data processing and
– a parallelogram for input/output activities.
1/7/2021 Structuring the logic: Sequential 70

Sequential Flow Chart

Sample Problems
• Find Simple Interest Rate and Compound
Interest Rate.
• Fin Sum and Average of Three Numbers.
• Find Engineering Cut-off mark.
• Find area of geometric shapes.
• Fruit Stall Problem

Formula to calculate area of geometric shapes

Fruit Stall Problem 1

Thank you
Structuring the logic: Sequential1/7/2021 77

Structuring the logic: Selection
By
Mr.S.Selvaraj

Selection / Decision Making
• Decision making is represented by the diamond which
accepts input from the top corner.
• For two-way decision making (say, for representing the
condition x > 5), two arrows emanate from the
bottom- and right-corner of this diamond.
• Example shows the flowchart for determining whether
a number is even or odd.
• The % (modulus) operator is used to compute the
remainder of a division, so n % 2 evaluates to 0 or 1,
while n % 3 evaluates to 0, 1 or 2.
• Complex decisions that need multiple IF statements
are represented by connecting multiple diamonds.
1/7/2021 Structuring the logic: Selection 79

Example

Sample Problems
• check whether the person is eligible to vote or not.
• Print the student result as whether PASS or FAIL.
• Print the Grade Points for the Subject Mark.
• Fruit Stall Problem.
• Traffic Light Problem.
• Energy Level Problem.

KEC Grading System

Fruit Stall Problem

Traffic Light Problem

Energy Level Problem

Thank you
Structuring the logic: Selection1/7/2021 86

Structuring the logic: Repetition
By
Mr.S.Selvaraj

Repetition
• There is no standard symbol for representing
repetition;
• a loop structure created by combining sequential and
decision-making symbols repeatedly executes a set of
instructions.
• Because the loop has to eventually terminate, a
conditional check must be made either at the
beginning or end of the iterative process.
• The most commonly used repetitive construct is the
while statement.
• Some languages also support variants like the for, until,
do-while and repeat constructs
1/7/2021 Structuring the logic: Repetition 88

Sample – Factorial Calcualtion

Problem 1
• Print sum of any ‘n’ numbers.
• Sample Output:
Enter the n value: 5
Enter 1 st Number : 15
Enter 2 nd Number : 20
Enter 3 rd Number : 25
Enter 4 th Number : 30
Enter 5 th Number : 20
Sum of the 5 Numbers are : 100

Problem 2
• Find the factorial of an number.
• Sample Output:
Enter the value: 5
Factorial of 5 is : 120

Problem 3
• Generate a table that displays a list of numbers and the square of those numbers.
• Ask the user how many numbers to include in the list
• Display the sum of all of the squares we compute.
• Sample Output:
How many Numbers should be in the table? 6
Number Square
=================
1 1
2 4
3 9
4 16
5 25
6 36
The sum of these squares is 91.

Problem 4
• Calculate TN engineering cut-off mark for ‘N’ students.
• Sample Output:
Enter the number of students to calculate cut-off mark: 5
================================================
Student Name Maths Phy Chem Cut-off
================================================
Kumar 80 60 60 140
Raj 90 90 90 180
Vidhya 100 100 100 200
Williams 50 80 65 122.50
Mohammed 60 100 75 147.50

Problem 5
• Generate the first N terms of Fibonacci sequence numbers.
• Sample output:
Enter the N value: 10
First 10 terms of Fibonacci numbers are:
0
1
1
2
3
5
8
13
21
34

Thank you
Structuring the logic: Repetition1/7/2021 95

Case Studies on Problem Solving
By
Mr.S.Selvaraj

Case Study 1: Exchanging the values of two variables
1/7/2021 Case Studies on Problem Solving 97

Case Study 1: Algorithm

Case Study 1: Pseudo Code

Case Study 1: Flowchart

Is it possible to solve the above
case study by without using
temporary variable ?

Case Study 2: Finding the maximum of N Numbers

Case Study 3: Reversing the Digits of an integer number

Sample Output
• Enter the Number to reverse: 1562
• The reversed number is : 2651

Thank you
Case Studies on Problem Solving1/7/2021 112

Programming Methodologies
By
Mr.S.Selvaraj

Introduction to Programming
• Programs should also be designed to be reusable.
• Most modern languages are procedural.
– They enable the execution of a section of code by
invoking the name assigned to the section.
– They also have separate names for these sections—
like routines, subroutines, procedures or functions.
• Another set of languages (like C++ and Java)
added the object flavor to change the
programming paradigm altogether.

Programming Methodologies
• These features allow the division of code into
separate modules using the following
programming methodologies to choose from:
– Top-down programming
– Bottom-up programming
– Object-oriented programming

Top-down programming
• A problem can be approached from the top to first
visualize the “big picture” before breaking it up into
separate components (top-down programming).
• C programming supports this approach for developing
projects. It is always good idea that decomposing
solution into modules in a hierarchical manner.
• The basic task of a top-down approach is to divide the
problem into tasks and then divide tasks into smaller
sub-tasks and so on.
• In this approach, first we develop the main module
and then the next level modules are developed.
• This procedure is continued until all the modules are
developed.

Top-down programming

Advantages of top-down approach
• In this approach, first, we develop and test most
important module.
• This approach is easy to see the progress of the project
by developer or customer.
• Using this approach, we can utilize computer
resources in a proper manner according to the project.
• Testing and debugging is easier and efficient.
• In this approach, project implementation is smoother
and shorter.
• This approach is good for detecting and correcting
time delays.

Bottom-up programming
• The individual components can be designed
first without fully knowing the big picture. The
components are later integrated to form the
complete system (bottom-up programming).

Bottom-up programming

Object-oriented programming
• The problem can be conceived as a collection of
objects where each object encapsulates both
data and the method used to access the data
(object-oriented programming—OOP).
• Advantages:
– No separate instructions are needed because these
objects encapsulate both data and instructions (called
methods) to access and manipulate the data.
– objects are reusable and easily interact with one
another.
– object-oriented programming is used for large and
complex projects.

Object-oriented programming

Thank you
Case Studies on Problem Solving1/7/2021 123

Structured Programming
By
Mr.S.Selvaraj

• Structured programming strives to achieve clarity,
faster development times and easy maintainability of
programs.
• It is an offshoot of procedural programming but goes
beyond the use of subroutines or functions to create
modular programs.
• Structured programs use
– control blocks (a group of statements that are treated as a
single statement) and
– loops (the repetition of one or more statements).
• These constructs are meant to replace the age-old
GOTO statement whose use has now been deprecated
(somewhat questionably though).
1/7/2021 Structured Programming 125

• The foundations of structured programming can be traced
back to the mathematicians Bohm and Jacopini.
• They proved in their structure theorem that any computing
problem can be solved by using only the following constructs:
– Sequencing (the execution of statements in sequence).
– Decision making (selection from among alternatives).
– Repetition (running one or more statements in a loop).

Structured Programming – Control Structures
• Following the structured program theorem, all
programs are seen as composed of control
structures:
– "Sequence"; ordered statements or subroutines
executed in sequence.
– "Selection"; one or a number of statements is
executed depending on the state of the program.
This is usually expressed with keywords such
as if..then..else..endif.

Structured Programming – Control Structures
• "Iteration"; a statement or block is executed until the
program reaches a certain state, or operations have
been applied to every element of a collection.
– This is usually expressed with keywords such
as while, repeat, for or do..until. Often it is recommended
that each loop should only have one entry point
• "Recursion"; a statement is executed by repeatedly
calling itself until termination conditions are met.
– While similar in practice to iterative loops, recursive loops
may be more computationally efficient, and are
implemented differently as a cascading stack.

Structured Programming Languages
• The languages that support Structured
programming approach are:
– C
– C++
– Java
– C#

Advantages of Structured Programming
• Easier to read and understand
• User Friendly
• Easier to Maintain
• Mainly problem based instead of being machine based
• Development is easier as it requires less effort and time
• Easier to Debug
• Machine-Independent, mostly.

Thank you
Structured Programming1/7/2021 131

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