How to decrease the amount of memory that a process/executable consume?

Think carefully about how you store your data; and use floats when doubles aren't needed, shorts and chars when they suffice; and avoid memory leaks; and perhaps trade running time for memory. Process files incrementally instead of loading them all at once, whenever you can.

As far as possible try to allocate memory only when required and dont use static data structures..
if ur talking abt the resources of the comp.. then make a 32 bit program.. and not a dos based 16 bit one..

How to decrease the amount of memory that a process/executable consume?

write less code :D look at the largest function(s) and see how (or if) they can be reduced.