Computational Thinking and Structure Chart Part 1 for O, A Level & IGCSE Computer by Inqilab Patel

Computational Thinking:
Abstraction – the process of extracting information that is essential, while ignoring what is not relevant, for the provision of a solution.
Decomposition – the process of breaking a complex problem into smaller parts.
Pattern recognition – the identification of parts of a problem that are similar and could use the same solution.
Q 1.1) What is meant by computational thinking?
Computational Thinking - is used to study a problem and formulate an effective solution that can be provided using a computer. There are several techniques used in computational thinking, including abstraction, decomposition, and pattern recognition.

Q 2) Define Decomposition, and give reason/benefits for decomposition.
Decomposition is the process of breaking down a complex problem into simple sub task.
Problem can be decomposed into following components:
 Input
 Process
 Output
 Storage.
For example, to calculate sum of two numbers program can be decomposed as follows:
Stage Pseudo code
INPUT INPUT Num1
INPUT Num2
PROCESS Sum  Num1 + Num2
OUTPUT OUTPUT Sum

Benefits of decomposition:
Program code is easier to implement.
Different people can be assigned to work on different modules or sub-tasks.
Program code is easier to test and debug.
Modules are re-usable.
Q) Define Abstraction.
Abstraction – the process of extracting information that is essential, while ignoring what is not relevant, for the provision of a solution.
Q) Describe need for and benefits of using abstraction, Describe the purpose of abstraction.
Abstraction involves filtering out information that is not necessary to solve a problem. Abstraction gives us the power to deal with complexity.
The benefits of abstraction:
• the time required to develop the program is reduced so the program can be delivered to the customer more quickly.
• the program is smaller in size so takes up less space in memory and download times are shortened.
• customer satisfaction is greater as their requirements are met without any extraneous features. 
7.2 Computer System
Q) What is system and sub-system?
A system is a set of rules, an arrangement of things, or a group of related things that work together to perform a function.
A system is made up of several subsystems. Each subsystem can be further divided into subsystems and so on until each sub-system just performs a single action.

Q) What is meant by computer system?
A COMPUTER SYSTEM is made up of hardware, software & data, communications and people; each computer system can be divided up into a set of sub-systems. Each subsystem can be further divided into sub-systems and so on until each sub-system just performs a single action.
Computer system is often divided up into sub-systems. This division can be shown using top-down design to produce structure diagrams that demonstrate the modular construction of the system.

Q) Define Top-Down Design
Top-down design is the breaking down 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.
This is an effective way of designing a computer system to provide a solution to a problem, since each part of the problem is broken down into smaller more manageable problems. The process of breaking down into smaller sub-systems is called ‘stepwise refinement’.
This structured approach works for the development of both large and small computer systems. When large computer systems are being developed this means that several programmers can work independently to develop and test different subsystems for the same system at the same time. This reduces the development and testing time.

 
7.2c Methods to design a Solution
Methods to design and construct a solution
Following are methods to design and construct a solution:
i. Structure Chart
ii. Flowchart
iii. Pseudo code

1. Structure Diagrams
The STRUCTURE DIAGRAM shows the design of a computer system in a hierarchical way, with each level giving a more detailed breakdown of the system into sub-systems.

2. Flowcharts
A FLOWCHART shows diagrammatically the steps required for a task (sub-system) and the order that they are to be performed. These steps together with the order are called an ALGORITHM. Flowcharts are an effective way to communicate the algorithm that shows how a system or sub-system works.
3. PSEUDO CODE is a simple method of showing an algorithm, using English-like words and mathematical operators that are set out to look like a program.