what is SDLC?

SDLC stands for software development life cycle. It explain complete life cycle about software 

development, software testing and software maintenance with some phases-'

1- Requirement gathering phase

2- Analysis phase

3- Designing phase

4- Coding phase

5- Testing phase

6- Delivery and maintenance phase

why software has bugs?

There are lot of reasons for defects in a software------
 
1- Programming errors.

2-software complexity.

3-miscommunicatins between clients and developers.

4-changing requirement continuously.

5- time pressures.

why software testing is needed?

for this we have so many reasons for testing the application some of them given below

1- To identify defects.
2- To avoid end user defecting problems.
3- To Prove that software has no fault.
4- To Prove that software works as per as customer requirements.
5- To Stay in business.

what is test data?

The value which are provides to the applications for testing called as test data.
we have two types of test data:-

1. Positive test data.

2. Negative test data.

what is requirement?

There is two types of requirement...
(1)Functional Requirement
(2)Non Functional Requirement

(1) Functional Requirement:- Performing operation on application and validity is called functional requirement.
For ex: Open Gmail Application
Enter valid username and password and click on ok button for login
Click on sign out button.
(2)Non Functional Requirement:- Non Functional requirement concern with application UI like field alignment,field spelling,Background color,Logo and so on.

what is the different among Error,Defect,Bug,Failure and Fault?

Error:- when a mistake in coding called is Error, it is found by developers.

Defect:- Error Found by tester called defect these are found by tester while testing the application.

Bugs:Bugs are found by end users while using the application or accepting the defect by the development team called bugs.

Failure:- when build does not meet the requirement then it is failure.

Fault:- An incorrect step, process, or data definition in a computer program which causes the program to perform in an unintended or unanticipated manner. See: bug, defect, error, exception.

what is requirement?

Customers or Clients requirements with respect to software are known as requirement.
There are two type of requirement-
(1) Functional requirement
performing operation on the application and validating known as functional requirement.

ex: open gmail.com login home page
enter the valid email id and password
(2)Non Functional requirement
validating the application layout known as non functional requirement.
ex:
application page overlapping
application page color
checking spelling etc.