org 100h

mainloop:
 jmp mainloop
ret    

format PE console 4.0 ;this tells you that it is PE (windows) and uses the console
;if you use console in this, then you will not have to use AllocConsole
include 'win32a.inc' ;macro package; you need to have the FASM include directory in your %INCLUDE% environment variable
entry start ;this tells you where the program starts, which is "start:" below.
section '.data' data readable writeable ;this is where you put your data. "readable writeable" sets access restrictions on this section.
;for this program, there is no data, so nothing goes here. You could also omit the previous line, since an empty section
;doesn't do anything and could cause the program to be un-runnable under some Windows installations.
section '.code' code readable executable ;think about it.
start: ;entry point
mainloop:
 jmp mainloop
;to exit the program:
invoke ExitProcess,0 ;this is a Windows API function call. You always use 'invoke' for API calls. 0 is the error level, normally use 0 for no error and >0 for error.
section '.idata' data readable ;this is a section for imports
;now, you have to define where the API calls are coming from. This is where this section comes in, you tell Windows what DLL you are importing from,
;and then you tell it which functions to import and where to put their addresses. FASM's macros then put labels where Windows puts the functions' addresses, so you can call them with invoke.
data import ;tells FASM this is an import block
library kernel32,'kernel32.dll' ;this tells you which DLLs to load. ExitProcess is in kernel32.dll, so you use that. For conversion from DOS->Windows, you'll probably only ever need kernel32, since it contains all command line access functions.
import kernel32,\ ;which DLL to import from
 ExitProcess,'ExitProcess' ;this function should be imported

;You could replace the 'import kernel32,.... ' part with "include 'apia\kernel32.inc' to save time, it automatically puts in all kernel32 functions for you.
;If you declare a function that you do not use, it is not included in the resulting file.
end data ;this is the end of the import section.
    

format PE console 4.0
entry main

section '.code' code readable executable
main:

 mainloop:
  jmp mainloop
 ret

 push 0
 call [ExitProcess]

section '.idata' data readable
 dd 0,0,0,RVA kernel32,RVA kernel32_import
 dd 0,0,0,0,0

 kernel32_import:
  ExitProcess dd RVA _ExitProcess
  dd 0

 kernel32 db 'KERNEL32.DLL',0
 _ExitProcess dw 0
  db 'ExitProcess',0    

now I just have to finish the part dealing with input and I'm ready

you make it sound easy

Quote:

now I just have to finish the part dealing with input and I'm ready

Try using MZ's instead (read the manual...)