Question: > 
> Not Counting the OS And the requirements to run the Development software. The storage space required.
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Strictly speaking from work perspective(company setup and not freelancers).A individual developer ( not considering a build system) unless into areas of video,audio processing( huge raw files) 3d/graphics development.
How much storage space would be required.

* Even if we account for the software trials to download or reading material.is it Right or Safe to assume 20GB would most suffice and any thing more would be a waste and or would be improperly utilized?.
* What is the typical hard disk space allotted per developer in an office setup.This may differ per role or specific requirement and on what type of work the company is into. but on an average for a developer/programmer how much space is normally allotted.

Edit: 

**To Clarify Intent** 

These are questions i had faced by business/management people.I only wish to understand more in this regard to give an answer(or better answer)the next time i come across them. I am neither making assumptions or intend to give offense to any one in this regard.It would be helpful if some links to data online were provided in this regard.

Edit 2:

* The issue as i understand was restricting the storage space to only the saving of work files to discourage extraneous usage...
* Not about scrimping/cost saving on hardware.

Answer: 
Actual space needed? It depends. Despite your edit I'm still not really sure I get the point. You couldn't even buy a 20gb hard drive right now if you tried. You would almost always use whatever size hard drive has best GB/$ ratio. (Or a small fast drive (SSD) and a large slower storage drive) Thats about a 1TB right now (last time I looked anyway...). If you wanted to drop to 500gb, you'd be paying 80% of the cost for 50% of the space. 

I would argue that somebody asking you to put a number on how much space you "need", doesn't even really understand what they are asking.
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> These are questions i had faced by
>  business/management people
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You do realize that modern internal harddisks cost something like ¢3-5/GB? So you're suggesting that ¢60 should be enough for developer. That's ridiculous, a sounds very dilbertian to make management issue out of it.