If I compile a file named "abc.cpp," what is abc.obj and what is abc.tds? Thanks

You must understand the dev cycle. When you compile a file you turn it into a .obj file. this is then linked (which is normally done automatically) into an .exe. check out the 'learning C' article about half-way down.

See, when u write a cpp file, u specify certain headers. Now, these headers need to be added(linked) to ur final program for it to work. This is done in the obj file. This obj will then be converted into a machine independent exe file. I dont know what tds is...

the .tds is probably compiler-specific.

Header files have nothing to do with linking. What vikram probably meant was libraries.

.tds files are specific to the borland compiler. You can safely delete them (the compiler will regenerate them if it needs them).