Algorithm and Problem Solving - IGCSE

Algorithm and Problem Solving

What will you Learn?

• The purpose of an algorithm and the processes involved in it

• Standard methods of solution

• Validation checks when data is input

• Verification checks when data is input

• Use of different types of test data including: Writing, amending, identifying, and correcting errors in:

• The stages in the program development cycle

• Computer systems and sub-systems

• Problem decomposition into component parts

• Methods used to design and construct solutions to problems

The program development life cycle is divided into five stages
analysis

1. Analysis

2. Design

3. Coding

4. Testing and

5. Maintenance

The program development life cycle

1. Analysis

This stage involves clear identification of the problem. It involves both abstraction and decomposition.
•Abstraction keeps the key elements required for the solution to the problem and discards any unnecessary details and information that is not required.
•Decomposition breaks down a complex problem into smaller parts, which can then be subdivided into even smaller parts, that can be solved easily.

2. Design

• The program specification from the analysis stage is used to show to how the program should be developed.

• When the design stage is complete, the programmer should know what is to be done.

• This stage involves flowcharts, pseudocodes

3. Coding and iterative testing

• The program or set of programs is developed.

• Each module of the program is written using a suitable programming language and then tested to see if it works.

• Iterative testing means that modular tests are conducted, code amended, and tests repeated until the module performs as required.

4. Testing

• The completed program or set of programs is run many times with different sets of test data. This ensures that all the tasks completed work together as specified in the program design.

Multiple Choice

Stage that involves the use of pseudocodes and flowcharts

• Design stage
• Coding stage

• Testing stage
• Maintenance stage

Multiple Choice

The process of selecting what you want and ignoring unwanted information

• Abstraction

• Analysis

• Selection

• Perceptual Set

Multiple Choice

What is the first phase of the program development lifecycle?

• Implementation

• Testing

• Requirements Analysis

• Maintenance

Multiple Choice

Which phase of the program development lifecycle involves creating a detailed plan for the project, including timelines and resource allocation?

• Design

• Implementation

• Planning

• Maintenance

Multiple Choice

What phase of the program development lifecycle focuses on making updates and improvements to the software to address issues and add new features?

• Testing
• Design
• Implementation
• Maintenance

Computer Systems

• A computer system comprises software, data, hardware, communications, and people; each can be divided into sub-systems.

• Each sub-system can be further divided into sub-systems until each sub-system performs a single action.

The computer system and its sub-systems

• In order to understand how a computer system is built up and how it works it is often divided up into sub-systems.

• Top-down design is the decomposition of a computer system into a set of subsystems, then breaking each sub-system down into a set of smaller sub-systems, until each sub-system just performs a single action.

Decomposing a problem

The component parts of any computer system are:

• Input

• Process

• Output

• •storage

Activity

• Use the alarm app to decompose and explain the following

• Input

• Process

• Output

• storage

Response

• inputs – time to set the alarm, remove a previously set alarm time, switch an alarm off, press snooze button

• processes – continuously check if the current time matches an alarm time that has been set, storage and removal of alarm times, management of snooze

• outputs – continuous sound/tune (at alarm time or after snooze time expired)

• storage – time(s) for alarms set.

Homework

Mention any one computer system you use frequently. Identify the input, processing, storage and output of the system you have mentioned.

Recap of the last lesson.

Multiple Choice

What is the primary purpose of an output device in a computer system?

• To process data
• To store data
• To input data
• To present data

Multiple Choice

Which component of a computer system is responsible for performing calculations and executing instructions?

• Input device

• Output device

• Central Processing Unit (CPU)

• Memory

Multiple Choice

Which of the following is a volatile storage device used for temporary data storage in a computer?

• Hard disk drive (HDD)

• Solid-state drive (SSD)

• Random Access Memory (RAM)

• Optical disc drive (ODD)

Multiple Choice

When you save a document on your computer's hard drive, which type of storage is being used?

• RAM
• ROM
• Flash Drive
• Hard Disk Drive

Multiple Choice

What is the primary function of an input device in a computer system?

• To store data

• To process data

• To display data

• To enter data into the computer

Multiple Choice

When you insert your ATM card into the machine and enter your PIN, which part of the computer system is responsible for processing this information?

• Input

• Output

• Storage

• Processing

Multiple Choice

Which part of the ATM system ensures the security of your financial transactions by encrypting and protecting your data?

• Input

• Output

• Processing

• Storage

Multiple Choice

When you withdraw cash from an ATM, which part of the computer system is responsible for retrieving the requested amount from your account?

• Input

• Output

• Processing

• Storage

Multiple Choice

Which stage of software development involves gathering and understanding the requirements of the system to be developed?

• Analysis

• Design

• Coding

• Testing

Multiple Choice

During the analysis and design stages, what documentation is typically created to describe the software system?

• Source code

• Test plans

• User manuals

• Flowcharts and diagrams

Multiple Choice

Which stage is responsible for ensuring that the software functions correctly and meets the specified requirements?

• Analysis

• Design

• Coding

• Testing

Multiple Choice

Which phase of software development involves the actual implementation of the software based on the design specifications?

• Analysis

• Design

• Coding

• Testing

Multiple Choice

During the coding stage, what do software developers primarily focus on?

• Gathering requirements

• Creating test cases

• Writing program code

• Documenting the system

Multiple Choice

Which stage of software development is often referred to as the "blueprint" phase, where the architecture and structure of the software are defined?

• Analysis

• Design

• Coding

• Testing

Multiple Choice

During the analysis stage, what is the primary goal?

• Writing code

• Creating user interfaces

• Defining system requirements

• Finding and fixing bugs

Methods used to design and construct a solution to a problem

The following are the methods used for design and construct a solution to a problem

• structure Diagrams

• Flowcharts

• Pseudocode

Structure diagrams

• Structure diagrams are hierarchical, showing how a computer system solution can be divided into sub-systems with each level giving a more detailed breakdown. If necessary, each sub-system can be further divided.

Flowcharts

• A flowchart shows diagrammatically the steps required to complete a task and the order that they are to be performed. These steps, together with the order, are called an algorithm.

• Flowcharts are drawn using standard flowchart symbols.

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Process flowchart symbols are used to show actions, for example, when values are assigned to variables.
Rectangle is used to show a process in a flowchart

Process

Terminator flowchart symbols are used at the beginning and end of each

flowchart.
An oval shape is used to show start or stop

Start or Stop (Begin/End)

Flowchart Symbols

Decision flowchart symbols are used to decide which action is to be taken next; these can be used for selection and repetition/iteration.
A diamond is used to show decision in a flowchart

Decision

The same symbol of input and output.
A Parallelogram is used to show input or output in a flowchart

Input and output

Cont..

Multiple Choice

In a flowchart, where would you find the result of a calculation or the output of a process?

• In the decision box
• In the start/end symbol
• In the process box
• In the output box

Multiple Choice

In a flowchart, where would you expect to find user-provided data or input?

• In a process box
• In an input/output box
• In a decision box
• In a start/end box

Multiple Choice

In a flowchart for a simple calculator program that adds two numbers, what would the addition operation be classified as?

• Input
• Output
• Process
• Decision

Multiple Choice

In a flowchart representing a program to find the largest number among three input values, what would the user-provided numbers be classified as?

• Input

• Output

• Process

• Decision

Multiple Choice

In a flowchart that calculates the area of a rectangle when given its length and width, what would the "Length" and "Width" be classified as?

• Input

• Output

• Process

• Decision

Multiple Choice

In a flowchart for a temperature conversion program that converts Celsius to Fahrenheit, what would the Fahrenheit temperature be classified as?

• Input
• Output
• Process
• Decision

Multiple Choice

In a flowchart for a program that calculates the average of a list of numbers, what would the computed average value be classified as?

• Input
• Output
• Process
• Data

Multiple Choice

In a flowchart representing a program that prints "Hello, World!" to the screen, what would the message "Hello, World!" be classified as?

• Input
• Output
• Process
• Decision

Multiple Choice

In a flowchart for a simple ATM withdrawal process, what would the action of dispensing cash to the user be classified as?

• Input
• Process
• Output
• Decision

Multiple Choice

In a flowchart for a simple calculator program, what would "Enter Number 1" be classified as?

• Input
• Output
• Process
• Decision

Multiple Choice

In a flowchart for a weather app that displays the current temperature, what would "Display Temperature" be classified as?

• Input
• Output
• Process
• Decision

Multiple Choice

In a flowchart for a program that calculates the area of a circle, what would be considered the "process"?

• Drawing the circle
• Defining the radius of the circle
• Calculating the area using the formula 'pi*r^2'
• Printing the result

Multiple Choice

In a flowchart for a simple calculator program that adds two numbers together, what would be considered the "process"?

• The display of the result
• The input of the numbers
• The addition of the two numbers
• The start of the program

Multiple Choice

In a flowchart for a temperature conversion program that converts Celsius to Fahrenheit, what would be considered the "input"?

• The conversion formula
• The Fahrenheit temperature
• The Celsius temperature
• The flowchart itself

Multiple Choice

In a flowchart for a program that prints the sum of all even numbers from 1 to 100, what would be considered the "output"?

• The sum of even numbers

• The even numbers themselves

• The loop that iterates through numbers

• The instruction to add numbers

Multiple Choice

In a flowchart for an ATM (Automated Teller Machine) withdrawal process, which of the following is most likely to be the output?

• The amount of money withdrawn
• The user's PIN (Personal Identification Number)

• ATM Card

• Bank Location

Multiple Choice

In a flowchart for a weather app, where the user inputs their location and the app provides the current temperature, what is considered as the output?

• The user's location.

• The temperature units (e.g., Celsius or Fahrenheit).

• The current temperature for the specified location.

• The app's logo.

Multiple Choice

In a flowchart for a login system, where users enter their username and password, and the system checks if they are correct before granting access, what represents the process?

• Entering the username and password.

• Checking if the entered username and password are correct.

• Granting access.

• Displaying a welcome message.

Multiple Choice

In a flowchart for a simple alarm clock, where users set the alarm time and the clock sounds the alarm at the specified time, what is considered as the output?

• The alarm clock's current time.

• The sound of the alarm.

• The snooze button.

• The user's preferred alarm time.

Multiple Choice

In a flowchart, what does a rectangle usually represent?

• A decision
• A process or operation
• A data
• A terminator

Multiple Choice

Which flowchart symbol is typically used to represent a decision point?

• Rectangle
• Diamond
• Circle
• Arrow

Multiple Choice

What symbol in a flowchart signifies the end of a process or program?

• Oval
• Rectangle
• Diamond
• Parallelogram

Flow lines

Flowchart flow lines use arrows to show the direction of flow, which is usually, but not always, top to bottom and left to right.

Flowchart Examples

1. sum of two numbers

2. simple interest

3. Area of a rectangle

4. Calculate age

5. Convert temperature from centigrade to fahrenheit

6. check whether a person is a child or adult

7. check the grade and display pass or fail

More Examples

8. flowchart for a calculator (+,-,*, and /)

9. Check if a number is a multiple of three or not.

1. Tickets are sold for a concert at $20 each, if 10 tickets are bought then the discount is 10%, if 20 tickets are bought the discount is 20%. No more than 25 tickets can be bought in a single transaction.

Homework