[Info-vax] VAX BASIC global variables.

[E Thump]

On Friday, October 15, 2021 at 1:36:11 AM UTC+1, Arne Vajhøj wrote:
> On 10/14/2021 8:23 PM, E Thump wrote: 
> > I come from BBC Basic where all variables are global unless 
> > explicitly defined as local to a sub/proc. 
> > 
> > VAX BASIC seems to operate the opposite way; IE variables by default 
> > are local. QB64 also seems to operate this way however in QB64, I am 
> > able to DIM SHARED [var_name] which makes a variable accessible 
> > globally. 
> > 
> > How do I accomplish the same in VAX BASIC? I want a variable declared 
> > at the top to be common throughout all the code, SUBs and all. At 
> > this time, I'm working with a single source file. 
> > 
> > I'm looking at the COMMON keyword but I can't see how that works for 
> > what I want, if at all it does!
> This program print 3: 
> 
> program comdemo 
> common (myarea) integer v 

Alright, thanks so I was on the right track with COMMON... what's the significance of myarea then?

I changed my program to this but it doesn't work as I want:
=====
External SUB adder (integer,integer)

common (myarea) integer a
common (myarea) integer b
a=100
b=200

print "a+b before sub: ",a+b
call adder (10,20)
print "a+b after sub: ",a+b

end program

sub adder (integer c,integer d)
a=400
b=1000
print "a+b in sub: ",a+b
print "c+d in sub: ",c+d
end sub
=====
yields:

a+b before sub:              300
a+b in sub:    1400
c+d in sub:    30
a+b after sub:               300