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What is dynamic memory allocation? How can we free the memory when variables are no longer in use?

+6 votes
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posted Dec 17, 2013 by Prachi Agarwal

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For more help => http://tech.queryhome.com/17148/how-free-will-calculate-no-of-bytes-it-need-to-free#.UrGcnvQW3kU
commented Dec 18, 2013 by Vikas Upadhyay

2 Answers

+1 vote

Dynamic memory allocation is where your program requests the allocation and use of memory from the operating system via the run-time library.

malloc - allocates the specified number of bytes
realloc - increases or decreases the size of the specified block of memory. Reallocates it if needed
calloc - allocates the specified number of bytes and initializes them to zero
free - releases the specified block of memory back to the system

answer Dec 17, 2013 by Satyabrata Mahapatra
0 votes

Dynamic memory allocation is where your program requests the allocation and use of memory from the operating system at run time based on the need of the process.

In C we can use malloc/calloc for allocation of the memory and free() to release it.
In C++ we can use new and delete operators to achieve the same(however malloc/calloc or free can also be used in C++)

answer Dec 17, 2013 by Salil Agrawal
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+4 votes
C: How to accessing structure member through pointer using dynamic memory allocation? 
printf ("%s %d %f\n", (*ptr+i).a, (*ptr+i).b, (*ptr+i).c);
[Error] invalid operands to binary + (have 'struct name' and 'int')

where ptr is a pointer to the structure and allocated dynamic memory using malloc. Any suggestion would be helpful.

Thanks in advance.

+3 votes
Memory allocation of variables in C? 
main {
 int a;
 a = 10;
}

Here, when the memory will be allocated.
Compile/Run time? why ?

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