#include append the main file, so you can just call your functions by name.
#insert is better and insert the source code at this place
i guess your example with line platform$=GetDeviceName() was not run through because include put it at the end of main file.
very useful is this once in main
#option_explicit
https://www.appgamekit.com/documentation/language/35_option_explicit.htm
if you are using global variables i suggest to use a type for it as collection
TYPE ScreenInfoType
a AS integer
b AS float
c AS string
ENDTYPE
Global ScreenInfo as ScreenInfoType
SetScreenInfo(ScreenInfo )
Screen.agc
Function SetScreenInfo(s ref as ScreenInfoType)
s.a= ...
s.b= ...
s.c= ...
EndFunction platform$
Function MyGetDeviceName()
platform$=GetDeviceName()
EndFunction platform$
main.agc
print (MyGetDeviceName())
print (GetDeviceName())
print(ScreenInfo.c)
AGK (Steam) V2017.08.16 : Windows 10 Pro 64 Bit : AMD (17.7.2) Radeon R7 265 : Mac mini OS Sierra (10.12.2)