[Web4lib] global variables versus local variables

[Karen Coyle]

When I was learning programming that had local and global variables, the 
local variables were billed as being more "safe" because other routines 
could not inadvertently modify or delete them. You chose local or global 
depending on the role of the data element in relation to the 
sub-routines, not based on efficiency. And with the speed of today's 
computers, the difference in efficiency between a global and a local 
variable may not be significant for most applications.

Others can undoubtedly explain this better than I.

kc

John Fitzgibbon wrote:

>Hi,
>
>When programming and when writing scripts, we are encouraged to use
>variables that are local in scope whenever we can.
>
>However, defining a variable within a sub-routine, as in VbScript, means
>the variable is defined every time the sub-routine is run whereas
>defining it outside the sub-routine means the variable is defined only
>once. Why is it more efficient to define a variable within a
>sub-routine?
>
>Also, defining a variable within a loop causes the variable to be
>defined afresh with each instance of the loop. Again this appears
>inefficient but is generally done when a 'for loop' is run in
>JavaScript.
>
>I don't doubt that local variables have their uses; I'm simply seeking
>an explanation.
>
>Regards
>John
>
>John Fitzgibbon
>
>John Fitzgibbon
>
>Galway Public Library
>Island House
>Cathedral Square
>Galway
>Ireland
>
>p: 00 353 91 562471
>f: 00 353 91 565039
>w: http://www.galwaylibrary.ie 
>
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Karen Coyle / Digital Library Consultant
kcoyle at kcoyle.net http://www.kcoyle.net
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