Dynamic memory allocation in C - Revision history

Proj user6 at 16:15, 27 April 2017

2017-04-27T16:15:19Z

Proj user14 at 20:01, 16 December 2016

2016-12-16T20:01:55Z

Proj user14: Created page with "Malloc ,Callloc, Realloc, free: 1)Malloc: Malloc dynamically allocates requested memory and returns pointer to it. /* We are allocating memory for..."

2016-12-16T19:43:57Z

Created page with "Malloc ,Callloc, Realloc, free: 1)Malloc: Malloc dynamically allocates requested memory and returns pointer to it. <syntaxhighlight lang="c"> /* We are allocating memory for..."

New page

Malloc ,Callloc, Realloc, free:

1)Malloc:
Malloc dynamically allocates requested memory and returns pointer to it.
<syntaxhighlight lang="c">
/* 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
</syntaxhighlight>

2)Calloc:
Calloc dynamically allocates requested memory and initializes it to zero.
Calloc is compiler independent.
<syntaxhighlight lang="c">

/* 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
</syntaxhighlight>

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.
<syntaxhighlight lang="c">
(void*) realloc(void *ptr ,sizeof(int));
</syntaxhighlight>

4)free:

After use of dynamically allocated memory, free the memory.
Consider below example:
int *ptr = (int *) malloc(n * sizeof(int));
//Use dynamically allocated memory

free(ptr);
ptr = NULL;// NULL represents address 0 and it can not be dereferenced so ptr can not be dereferenced.

@@ Line 19: / Line 19: @@
 ) '''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.
+Realloc can be used as a substitute to malloc or free.
 <syntaxhighlight lang="c">
 int *ptr1 = (int *) realloc(ptr ,4*n*sizeof(int));  //dynamically allocated memory by malloc at pointer "ptr" will be increased 4 times in size.

@@ Line 1: / Line 1: @@
 Malloc ,Callloc, Realloc, free:
-)Malloc:
+) '''Malloc''':
 Malloc dynamically allocates requested memory and returns pointer to it.
 <syntaxhighlight lang="c">
@@ Line 8: / Line 8: @@
 </syntaxhighlight>
-)Calloc:
+) '''Calloc''':
 Calloc dynamically allocates requested memory and initializes it to zero.
 Calloc is compiler independent.
@@ Line 17: / Line 17: @@
 </syntaxhighlight>
-)Realloc:
+) '''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.
 <syntaxhighlight lang="c">
-(void*) realloc(void *ptr ,sizeof(int));
+int *ptr1 = (int *) realloc(ptr ,4*n*sizeof(int));  //dynamically allocated memory by malloc at pointer "ptr" will be increased 4 times in size.
 </syntaxhighlight>
-)free:
+) '''free''':
-After use of dynamically allocated memory, free the memory.
+After use of dynamically allocated memory, free the memory.<br>
 Consider below example:
-int *ptr = (int *) malloc(n * sizeof(int));
+<syntaxhighlight lang="c">
-//Use dynamically allocated memory
+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.