program headers linker script

by "headers", I assume you mean a header, or a *.h file... if you will ever notice, a header file (although I have seen this abused), never contains executable code, just compiler directives (those are the things that start with a # sign, such as #define, #pragma, #include, etc.) .......... i have seen executable code in a header file, but i personally consider it very bad practice.. Why would you use headers? to keep your little compiler f*ck-yous away from the actual code, is the best way I can think of putting it........

The headers are needed for loading. The simplest is you have a text,data and bss section in your file. But if you have something special in your file, you might want to tell the loader where to find it (e.g. a relocation table).