>Dear Experts
>
>Q.No.1, What is meaning of following line?
>Textbox::GotFocus()

it calls the base class GotFocus()

>Q.No.2, What is difference between Nodefault and Dodefult?

DODEFAULT() call the method of the base class, NODEFAULT prevents the method of the base class to run

>Q.No.3,When the following command is used?
>_VFP.AutoYield=.f.

Mostly to run ActiveX Controls. This prevents ActiveX events to run between 2 VFP instructions.

>Q.No.4, What is difference between following two command
>SET CLASSLIB TO myclslib
>SET CLASSLIB TO myclslib ADDITIVE

the 2nd line add myclslib to the existing list of class libraries. The first one overwrite the list.

>Q.No.5, What is difference among Locate,seek and scan?
>Please give some examples to find specific data from a dbf while using above three commands.Suggest also what is better and faster.

SEEK is faster than LOCATE if LOCATE can't be rushmore optimized. Same goes with SCAN that need rushmore with the FOR clause.
Ex:

SEEK "Answers"
SCAN WHILE var = "Answers"
   * processing
ENDSCAN

SCAN FOR var = "Answers"
   * processing
ENDSCAN

LOCATE FOR var = "Answers"

>Q.No.6, What is difference among local,public and private variables? Please also give some examples.

It's the scope of the variable.
PUBLIC vars are not scoped, they are available anywhere unless they are made PRIVATE during a call to a procedure.
PRIVATE vars are scoped to the local procedure and all the called procedure.
LOCAL vars are only scoped to the local procedure.

>Wish you good Luck

Is that a questionnaire of your own, or you have to answer these questions ?