Is it always important to include the file "startup.a51"? Should anything else be included for it to work properly? Thanks
LJMP ?C_STARTThis code jumps to the start of your C code -- that is, main(). Not quite. C_START is the start of Keil's 'C' runtime startup: this includes, among other things, the code to setup all the values of initialised variables. Once this code has completed, it then jumps to main(). As someone else mentioned earlier, you can step through all this if you want...
LJMP ?C_START