[Info-vax] VAX BASIC global variables.

[Dave Froble]

On 10/15/2021 12:56 PM, Arne Vajhøj wrote:
> On 10/15/2021 12:09 PM, E Thump wrote:
>> On Friday, October 15, 2021 at 4:44:49 PM UTC+1, Jeffrey H. Coffield
>> wrote:
>>> COMMON (MY_DATA) INTEGER a,b
>
>>> sub adder (integer c,integer d)
>
>> Next question to do with arrays. Instead of doing DIM Z(10) it seems
>> I should do COMMON (MY_DATA) INTEGER Z(10) and then use that exact
>> same line within the sub. The 10 and everything has to match. Am I on
>> the right lines there?
>
> Yes.
>
> Declarations *should* match.
>
> They are not strictly required to, but it becomes
> pretty messy if they don't.
>
> This does not look good:
>
> program hack
> common (mydata) long a(2)
> call s
> print a(0),a(1)
> end program
>
> sub s
> common (mydata) word a(4)
> a(0) = 1
> a(1) = 1
> a(2) = 2
> a(3) = 2
> end sub
>
>
> Arne

In Arne's example, the linker will allocate space for the 4 element array,
but the main program will not be able to address a(3).

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David Froble                       Tel: 724-529-0450
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