My following C code is not working...
how? What does it do?
This is my first C program, What it does is jsut toggles the output at 2 ports. No much significance.
If it "toggles the output at 2 ports" it works!.
what DOES it do, not what is it SUPPOSED to do?

Does "void LongDelay();" not give you a warning or an error?
No there are no errors or warning messages.
There must be, it is wrong, should be:
void LongDelay(void);"

I made some changes for to STARTUP.A51 after going through http://www.keil.com/support/docs/2659.htm
but still my code doesnt work.
This is done only to understand the C environment...
DO NOT try to understand "the C environment" before you understand C.

Let Keil handle "the C environment" for you and get the C to work. I did Keil C for years before I had any reason to "study" "the C environment".

When you have problems, solve the problems instead of getting sidetracked by "studying environments". Most PC C programmers probably do not even know that such an animal exist.

Erik