-s-
C code requires a small startup file containing system initialization code to be executed before entering main. The standard startup code is found in the object file $(InstallDir)/lib/crt0.hzo and the compiler driver automatically links this into your program. If, however, you do not require the standard startup code because you have a pure assembly language application, you can request the compiler driver to exclude this standard startup code from the link using the -s- option.
You will find the source code for the standard startup module crt0 in the file $(InstallDir)/src/crt0.asm.