Dynamic memory allocation
- 2. Dynamic memory allocation refers to performing manual memory management for dynamic memory allocation in the C programming language via a group of functions in the C standard library. C Dynamic Memory Allocation 01010010 01000001 01001011 01001001 01000010
- 3. Why Dynamic Memory Allocation ? In many situations the programmer requires greater flexibility in managing the lifetime of allocated memory. 01010010 01000001 01001011 01001001 01000010
- 4. As you know, an array is a collection of a fixed number of values. Once the size of an array is declared, you cannot change it. Sometimes the size of the array you declared may be insufficient. To solve this issue, you can allocate memory manually during run-time. This is known as dynamic memory allocation in C programming. 01010010 01000001 01001011 01001001 01000010
- 5. Overview of functions Function Description malloc() allocates the specified number of bytes realloc() increase or decrease the size of the specific block of memory , moving it if necessary calloc() allocates the number of bytes and initialize them to zero free() releases the specified block of memory back to system The C dynamic memory allocation functions are defined in stdlib.h
- 6. The name "malloc" stands for memory allocation. C malloc() 01010010 01000001 01001011 01001001 01000010 Syntax of malloc() Example The malloc() function reserves a block of memory of the specified number of bytes. And, it returns a pointer of void which can be casted into pointers of any form.
- 7. The name "calloc" stands for contiguous allocation. C calloc() 01010010 01000001 01001011 01001001 01000010 Syntax of calloc() Example The malloc() function allocates memory and leaves the memory uninitialized. Whereas, the calloc() function allocates memory and initializes all bits to zero.
- 8. C free() 01010010 01000001 01001011 01001001 01000010 Syntax of free() Dynamically allocated memory created with either calloc() or malloc() dosen’t get freed on their own. You must explicitly use free() to release the space. This statement frees the space allocated in the memory pointed by ptr .
- 9. C realoc() If the dynamically allocated memory is insufficient or more than required, you can change the size of previously allocated memory using the realloc() function. Syntax of realloc() Here ptr is reallocated with a new size x . 01010010 01000001 01001011 01001001 01000010
- 10. Usage examples Creating an array of ten integers with automatic scope is straightforward in C: However, the size of the array is fixed at compile time. If one wishes to allocate a similar array dynamically, the following code can be used: 01010010 01000001 01001011 01001001 01000010
- 11. Because malloc() might not be able to service the request , it might be return a null pointer and it is good programming practice to check this: When the program no longer needs the dynamic array, it must eventually call free to return the memory it occupies to the free store:
- 12. With realloc we can resize the amount of memory a pointer points to. For example, if we have a pointer acting as an array of size n and we want to change it to an array of size m, we can use realloc. Note that realloc must be assumed to have changed the base address of the block . 01010010 01000001 01001011 01001001 01000010
- 13. Example 1: malloc() and free() Here, we have dynamically allocated the memory for n number of int . 01010010 01000001 01001011 01001001 01000010
- 14. Example 2: calloc() and free() 01010010 01000001 01001011 01001001 01000010
- 15. Example 3: realloc() When you run the program, the output will be: 01010010 01000001 01001011 01001001 01000010
- 16. THANK YOU 01010010 01000001 01001011 01001001 01000010 01010010 01000001 01001011 01001001 01000010