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System Analysis & design

Ms. JYOTI

ASSISTANT PROFESSOR COMPUTER SCIENCE & IT DEPT

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Introduction To SAD:�Systems development is systematic process which includes phases such as planning, analysis, design, deployment, and maintenance. Here, in this tutorial, we will primarily focus on −��1. Systems analysis�2. Systems design�

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Systems Analysis�

It is a process of collecting and interpreting facts, identifying the problems, and decomposition of a system into its components.
System analysis is conducted for the purpose of studying a system or its parts in order to identify its objectives.
It is a problem solving technique that improves the system and ensures that all the components of the system work efficiently to accomplish their purpose.

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Systems Design�

It is a process of planning a new business system or replacing an existing system by defining its components or modules to satisfy the specific requirements.

System Analysis and Design (SAD) mainly focuses on −
Systems
Processes
Technology

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Constraints of a System�

A system must have three basic constraints −

A system must have some structure and behavior which is designed to achieve a predefined objective.

Interconnectivity and interdependence must exist among the system components.
The objectives of the organization have a higher priority than the objectives of its subsystems.

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Elements of a System�

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Outputs and Inputs�

The main aim of a system is to produce an output which is useful for its user.
Inputs are the information that enters into the system for processing.
Output is the outcome of processing.

Processor:

The processor is the element of a system that involves the actual transformation of input into output.
It is the operational component of a system. Processors may modify the input either totally or partially, depending on the output specification.

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Control�

The control element guides the system.
It is the decision–making subsystem that controls the pattern of activities governing input, processing, and output.

Feedback:

Feedback provides the control in a dynamic system.
Positive feedback is routine in nature that encourages the performance of the system.
Negative feedback is informational in nature that provides the controller with information for action.

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Environment�

The environment is the “supersystem” within which an organization operates.
It is the source of external elements that strike on the system

Boundaries and Interface

A system should be defined by its boundaries. Boundaries are the limits that identify its components, processes, and interrelationship when it interfaces with another system.
Each system has boundaries that determine its sphere of influence and control.

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Types of Systems�

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Physical or Abstract Systems�

Physical systems are tangible entities. We can touch and feel them.
Physical System may be static or dynamic in nature. For example, desks and chairs are the physical parts of computer center which are static.
A programmed computer is a dynamic system in which programs, data, and applications can change according to the user's needs.

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Open or Closed Systems�

An open system must interact with its environment. It receives inputs from and delivers outputs to the outside of the system. For example, an information system which must adapt to the changing environmental conditions.

A closed system does not interact with its environment. It is isolated from environmental influences. A completely closed system is rare in reality.

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�Adaptive and Non Adaptive System�

Adaptive System responds to the change in the environment in a way to improve their performance and to survive. For example, human beings, animals.

Non Adaptive System is the system which does not respond to the environment. For example, machines.

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�Natural and Manufactured System�

Natural systems are created by the nature. For example, Solar system, seasonal system.

Manufactured System is the man-made system. For example, Rockets, dams, trains.

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System Testing�

System Testing (ST) is a black box testing technique performed to evaluate the complete system the system's compliance against specified requirements.

In System testing, the functionalities of the system are tested from an end-to-end perspective.
It includes both functional and Non-Functional testing.

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Types of System Tests:�

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Testing Principles�

All tests must satisfy the customer's needs.
To make our software testing more efficient, we should use a third party.
It is impossible to do exhaustive testing. We need the optimum quantity of testing depending on the application's risk assessment.
All tests that will be undertaken should be prepared before they are carried out.
Begin with minor components and work your way up to larger ones.

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Unit Testing�

It concentrates on the tiniest aspect of software development. This is where we test a single unit or a collection of interconnected units.

The programmer often does this task by utilising sample input and seeing the accompanying results.

In a programme, we check to see whether the loop, method, or function is operating properly.

Arithmetic precedence is misunderstood or erroneous.

Incomplete or incorrect initialization

Benefits of Unit Testing

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Integration Testing�

The goal is to take unit-tested components and use them to create a programme structure that is determined by design. Integration testing entails combining a number of components to achieve a result.
There are four kinds of integration testing −
From the top down
From the bottom up
Sandwich
Big-Bang