View source for Dynamic memory allocation in C

Malloc ,Callloc, Realloc, free:

1) '''Malloc''':
Malloc dynamically allocates requested memory and returns pointer to it.
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/* We are allocating memory for "n" integers and returns integer pointer */
int *ptr = (int *) malloc(n * sizeof(int)); // We have type casted pointer to int
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2) '''Calloc''':
Calloc dynamically allocates requested memory and initializes it to zero.
Calloc is compiler independent.
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/* We are allocating memory for "n" integers and returns integer pointer */
int *ptr = (int *) calloc(n,sizeof(int)); // We have type casted pointer to int
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3) '''Realloc''':
Realloc is used when we have dynamically allocated memory and need to resize it.
Realloc can beused as a substitute to malloc or free.
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int *ptr1 = (int *) realloc(ptr ,4*n*sizeof(int));  //dynamically allocated memory by malloc at pointer "ptr" will be increased 4 times in size.
ptr1 = (int *)realloc(ptr1,0); //use realloc as free
int *ptr2 = (int *)realloc(NULL,n*sizeof(int)); //used as malloc

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4) '''free''':

After use of dynamically allocated memory, free the memory.<br>
Consider below example:
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free(ptr); // space pointed by pointer "ptr" is made available but the content in space is unchanged.
ptr = NULL;// NULL represents address 0 and it can not be dereferenced so ptr can not be dereferenced.
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