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Easy (I hope) Visual C++ question- Why NEW?

Posted on 2000-02-22
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 Ok- hopefully, this is an easy question.  I'm trying to learn Visual C++ 6.0 from books (Couldn't find a local course on it that wasn't full) and I've got a few questions.  For now, though, here's one-
   Why use the NEW command when initializing variables and classes?  For example, why say "new int a;" instead of "int a;"?  
   I've consulted 3 books, and so far the only difference that they tell me is that I've got to use the delete command after I'm done with them or else I get a memory leak.  This seems more like a disadvantage than anything else, so what advantages does the NEW command provide?
-Delion
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Question by:Delion
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nietod earned 30 total points
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new creates data "dynamically" instead of "locally".  local data is contained in a scope, usually the scopy of a function  When that function ends the data is destroyed.  But dynamic data exists until it is destroyed (with delete).  So you can use new to allocate data within a function and have that data continue to exist after the function ends.  There are many times when this sort of thing is needed.
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by:nietod
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A 2nd advantage of dynamically allocated data is that it can be allocated in arrays whose sizes are determined at run-time.  For example, if you want to read a text file into a character array, you could declare the array like

char TextArray[1000];

but what if the file is more than 1000 characters long?  Well, you could declarre it to be 10000 characters long, but that might still not be enough.  What is more, if the file is short, say only 100 characters, then 10000 characters would be a terrible waste of space.  So you can use "new" to allcoate an array of just the right size once you learn the needed size at run-time.
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by:Delion
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