Re: Hardware independent programming

[ldries46 <bertus.dries@planet.nl>]

Op 29-6-2020 om 6:42 schreef ldries46:
> Hardware can in some cases have limits you have to consider when 
> writing a program.
>  At this moment I can mention three:
>
> 1. The printer. The format of the documents you want to print must fit
>    on the printers available to the user. In general the problem is
>    solved by the possibility of printer drivers to shrink you document
>    f.i. from A4 to A4 or saving the document to a file that can be
>    printed elsewhere.
> 2. The monitor on the system your program is running. Creating a window
>    that is to large for your screen resolution can be trouble some but
>    you do not know the resolution of the the customer using your
>    program. The solution for such a problem can only be hardware
>    independent programming. Your program should know the resolution of
>    your screen and adjust to  that or in the worst case decide that
>    system is not suitable for the program.
> 3. The available memory. Your program will in some cases need to know
>    the limits to which the heap stretches within the memory (in cases
>    where it is necessary  to use very large bulks of data). For
>    operating systems that have the possibility to stretch the heap with
>    a part on disc both boundaries (with and without disc data) are of
>    interest.
>
> There should be a package in Ada that like GNAT.OS-lib does with 
> operating system differences, makes such hardware parameters available 
> for the programmer.
>
If we want to create hardware or operating system independent programs 
it is in some situations necessary to use environmental variable from 
which a package in Ada or in other languages can get values from.
The names of these values should then in all these systems the same. I 
found that in Windows OS is such a variable for the name of the 
operating system (OS=Windows_NT) In Linux(Ubuntu) I could not find such 
a variable so it looks logical to use OS=Linux. For other parameters 
standard names should be found. So the ada packages I mentioned is not 
the only thing that must be done.