Stubs - A Piece of code that simulates the activity of the 
missing component. stub is used to test a unit in isolation.

Or A stub is a piece of software that works similae to the 
unit which is referenced by the unit being tested

Or A stub is a pseudo-module emulating the functionality of 
a not yet implemented or integrated component.

Driver - A Piece of code that passes the test case to 
another piece of code. Driver Program only calls the 
function being developed but possibly manyn times to test 
its behaviour on the variety of parameters.

Vinodh Anandan
Software Tester
Exceed Technologies (P) Ltd.,
Chennai

while integrating in top down approach any compulsory module
are missed replaced with temporary programmes known as stubs

stub and driver are temporary programes while we executing 
the programe if any module was underconstructed. here stub 
is a calling programe. driver is a called programe