What is the difference between TCP/IP model and OSI model?

What is the difference between TCP/IP model and OSI model?

OSI-model	TCP-IP-Model
7.  Application layer	4.  Application layer
6.  Presentation layer
5.  Session layer
4.  Transport layer	3.  Transport layer
3.  Network layer	2.  Network layer
2.  Data link layer	1. Physical layer
1.  Physical layer

Level 7 - Application: According to the requirement, this level works with the application software to provide communication functions to check the availability of communication partners and resources to support any data transfer. The Domain Name Service (DNS), File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), Internet Message Access Protocol (IMAP), Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), Telnet, and Terminal Emulation.

Layer 6 - Presentation: This layer ensures the data is compatible with the communication resources. It ensures compatibility between the data formats on the levels of apps and the lower layers. It handles any data formatting or code conversion as well as data compression and encryption

Layer 5 - Session: Layer 5 Software Handle Authentication and Authorization Functions. It also manages connectivity between both communication devices, establishes a connection, maintains a connection, and closes it in the end. This layer ensures that the data is distributed as well.

Level 4 - Transport: This level provides quality service (QoS) functions and ensures full distribution of data. Data is collected at this level through error correction and similar functions.

Level 3 - Network: Network layer handles packet routing through logical addressing and switching functions.

Layer 2 - Data Link: Unpack data in Layer 2 Operations package and Frames.

Layer 1 - Physical: This layer defines the logic level, data rate, physical medium, and data conversion functions, which make the bitrate of the packet from one device to another.

software engineering Verification and Validation (V&V) ?

 Verification and Validation (V&V) ?

Verification	Validation
Are We Building a System?	Are We Making the Right System?
Verification is the process of evaluating the development phase products to find out whether or not to meet the specified requirements.	Validation is the process of evaluating software at the end of the development process to determine whether software meets the customer expectations and requirements.
The purpose of the test is to ensure that the product is developed according to the requirements and design specifications.	The purpose of the belief is that the product actually meets the needs of the user and check whether the features are correct in the first place.
The following activities include in verification: reviews, meetings and observations.	Validations include the following activities: test like black box test, white box test, grey box test etc.
Verification is carried out by the QA team to check whether the quality software is in accordance with the documentation.	Validation is carried out by testing team.
Execution of code is not comes under Verification.	Execution of code is comes under Validation.
The verification process specifies whether the output is according to inputs.	The validation process describes whether the software is accepted by the user or not.
Verification is carried out before the Validation.	Validation activity is carried out just after the Verification.
The following things are evaluated during testing: plans, requirement specifications, design specifications, codes, test cases etc.	During validation the following items are evaluated: under real-life testing or software.
Cost of errors caught in Verification is less than errors found in Validation.	Cost of errors caught in Validation is more than errors found in Verification.
It is actually a manual check of files like documents and requirements.	It is basically checking out the programs developed based on the requirement specification documents and files.

What do you mean by empirical estimation models? Explain COCOMO model with suitable example?

What do you mean by empirical estimation models? Explain COCOMO model with suitable example?

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Stands for Constructivie Cost Model

As with all estimation models, it requires sizing information and accepts it in three forms: object points, function points, and lines of source code.

Application composition model - Used during the early stages of software engineering when the

following are important

– Prototyping of user interfaces

– Consideration of software and system interaction

– Assessment of performance

– Evaluation of technology maturity

Early design stage model – Used once requirements have been stabilized and basic software architecture has been established

Post-architecture stage model – Used during the construction of the software

Organic, Semidetached and Embedded software projects

• Organic: A development project can be considered of organic type, if the project deals with developing a 
  well understood application program, the size of the development team is reasonably small, and the 
  team members are experienced in developing similar types of projects.

• Semidetached: A development project can be considered of semidetached type, if the development 
  consists of a mixture of experienced and inexperienced staff. Team members may have limited 
  experience on related systems but may be unfamiliar with some aspects of the system being developed.

• Embedded: A development project is considered to be of embedded type, if the software being developed is strongly coupled to complex hardware, or if the stringent regulations on the operational 
  procedures exist.

The basic COCOMO model gives an approximate estimate of the project parameters. The basic COCOMO

estimation model is given by following expressions:

Effort = a1 x (KLOC)a2 PM (person Month)

Time of Development = b1 x (Effort) b2 Months

Where, a1,a2,b1,b2 are constants for each category of software products

Estimation of Effort

Organic: Effort = 2.4 (KLOC) 1.05 PM

Semi-detached: Effort = 3.0 (KLOC) 1.12 PM

Embedded: Effort = 3.6 (KLOC) 1.20 PM

Estimation Time of Development

Organic: Time of Development = 2.5 (Effort) 0.38 Months

Semi-detached: Time of Development = 2.5 (Effort) 0.35 Months

Embedded:Time of Development = 2.5 (Effort) 0.32 Months

Example:

Assume that the size of an organic s/w product has been estimated to be 32,000 lines of source code. Assume that the average salary of software be Rs. 15,000/- month. Determine the effort required to develop the software product and the nominal development time.

Effort= 2.4 x (32) 1.05 = 91 PM

Time of development = 2.5 x (91) 0.38 = 14 months

Cost= 14 x 15,000 = Rs. 2,10,000/-

Differentiate between Black Box Testing and White Box Testing with suitable Example

Differentiate between Black Box Testing and White Box Testing with suitable Example

Black Box Testing	White Box Testing
Black Box Testing is a software testing method in which the internal structure/ design/ implementation of the item being tested is not known to the tester. Tester is mainly concerned with the validation of output rather than how the output is produced (functionality of the item under test is not important from tester's pov).	White Box Testing is a software testing method in which the internal structure/ design/ implementation of the item being tested is known to the tester. Tester validates the internal structure of the item under consideration along with the output.
Which is not necessary in Black Box testing.	Programming knowledge and implementation knowledge (internal structure and working) is required in White Box testing,
Black box testing is done by the professional testing team and can be done without knowledge of internal coding of the item.	White Box testing is generally done by the programmers who have developed the item or the programmers who have an understanding of the item's internals.
Internal system design is not considered in this type of testing.	Internal software and code working should be known for this type of testing.
It is a software testing method where in testers are not required to know coding or internal structure of the software.	This testing is based on knowledge of the internal logic of an application’s code.
Tests are based on requirements and functionality.	White box testing approach is used in Unit testing which is usually performed by software developers.
Black box testing method relies on testing software with various inputs and validating results against expected output.	White box testing is also known as clear box testing, transparent box testing and glass box testing.
Tests are conducted at the software interface.	It is predicated on close examination of procedural detail.
Black box testing is a testing strategy based solely on requirements and specifications. Black box testing requires no knowledge of internal paths, structures, or implementation of the software being tested.	White box testing is a testing strategy based on internal paths, code structures, and implementation of the software being tested. White box testing generally requires detailed programming skills.

Black-box Testing (functional)

Can you see what’s inside a closed black-box? No, right? Similarly Black-box method treats the AUT as a black-box (no knowledge about its internal structure). Result – We are not bothered about how the internal structure of the application is maintained/changed until the outside functionality is working as expected (as per requirements). Knowing what the application does is more important than knowledge of how it does it. This is the most widely used test method for System & Acceptance tests as it doesn’t require professionals with coding knowledge and also it provides an external perspective of the AUT (as an end-user who have no knowledge of the actual code).

E.g. we are only concerned if user can watch television, change channels & volume, etc.

White-box Testing (structural)

It’s obvious, just reverse the approach. Since it’s a White-box >> we can see what’s in it, i.e. the internal structure, and use that knowledge to expand the coverage to test every possible flow at code-level. For example – Statement coverage, Branch coverage or Path coverage. It requires programming skills and is usually preferred only for Unit & Integration test levels. You can call it by different names – Clear-box, Glass-box or Transparent-box as far as you can see the internal contents of the box :-).

E.g. we are concerned if the internal circuit for the television is designed correctly.

Explain the three golden rules that form the basis of interface design software engineering?

Golden Rules of Mandal

Golden rules are divided into three groups:

1. Place users in control
2. Reduce users' memory load
3. Create Interface Concentant

Each of these groups includes specific rules. The rules for each set (and the main word for each rule) are:

(1) Place Users in Control

• Use Methods Critically (Model)
• Users keyboard or mouse (flexible)
• Allow users to change the faux (interactive)
• Show descriptive messages and text (useful)
• Provide immediate and irreversible actions, and respond (leniency)
• Meaningful paths and exit (navigable)
• Accommodate users with different skill levels (accessible)
• Make User Interface Transparent (Feature)
• Allow users to customize the interface (preferences)
• Allow user direct objectives (interactive) to interface objects.

(2) Reduce Users’ Memory Load

• Short-term memory (remember)
• Depends on belief, do not remember (belief)
• Provide visual signals (report)
• Provide default, undo and redo (sorry)
• Provide interface shortcut (Frequency)
• Encourage Object-Action Syntax (Unobtrusive)
• Use real locations (migration)
• User Progressive Advertising (Reference)
• Encourage visual clarity (organize)

(3) Make the Interface Consistent

• Maintain the context of users' functions (continuity)
• Maintain consistency within the product and overall (experience)
• Keep the interaction results the same (expectations)
• Artistic appeal and integrity (attitude)
• Research promotion (predictable)