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Dynamic Memory Allocation in C: A Comprehensive Guide

When you declare a variable or an array of a data type, the space occupied by them in the memory of the system remains constant throughout the program. At times, the constant space allocated during compile-time isn’t enough. In that case, the concept of dynamic memory allocation in C comes to the rescue. Learn more about dynamic memory allocation from this article. 

Table of Content:

• What is Dynamic Memory Allocation, and Why Is It Needed in C?
• Understanding the Difference Between Static and Dynamic Memory Allocation
• Dynamic Memory Allocation in C
• Malloc() Vs Calloc()
• Conclusion
• FAQs

What is Dynamic Memory Allocation in C?

Dynamic memory allocation involves the manual allocation and clearing of memory as per programming requirements. Dynamic memory in C gets managed and served with pointers pointing toward the newly allocated memory space in the heap area. 

This concept helps with memory allocation in C even during run-time without any hassle. While automatic memory management leverages the stack, dynamic memory allocation in C uses the heap.

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Understanding the Difference Between Static and Dynamic Memory Allocation

Here is a list of difference between static and dynamic memory allocation in C:

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Dynamic Memory Allocation in C

The <stdlib.h> library comes with the following functions that support dynamic memory allocation:

The Malloc() Function

The malloc() function is primarily used for dynamic memory allocation in C. This function helps allocate a memory block dynamically. It conserves memory space of a particular size. It delivers a null pointer that points to the memory location. 

The returned pointer is usually of the void type. Therefore, you will be able to assign the C malloc() function to all pointers. 

Syntax of Malloc()

The syntax of malloc() dynamic memory allocation in C is as follows:

The ptr refers to a pointer of cast_type. The C malloc() function delivers a pointer to the allocated memory of byte_size. 

The malloc() function in dynamic memory allocation is used with the character data type along with complex data types like structures. 

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C Calloc() Method

The calloc or contiguous allocation method helps with the dynamic memory allocation of a specified number of blocks of a particular type. The calloc method for dynamic memory allocation in C is quite similar to the malloc method. However, you will come across some primary differences between the two, which are as follows:

• The calloc method comes with two arguments or parameters.
• The calloc method initializes every block with a default value of 0. 

Syntax of C Calloc

The syntax for the calloc() method for dynamic memory allocation in c is as follows:

In this case, n refers to the number of elements. Meanwhile, element size describes the size of every element. 

In case the space isn’t enough, the allocation will fail and deliver a NULL pointer.

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The Free() Function

The free() method for dynamic memory allocation is primarily used for deallocation. It can help you dynamically deallocate the memory. The memory allocated using the different methods for memory allocation in C does not get deallocated on its own. Therefore, the free method can help with minimzing memory wastage by freeing it. 

Syntax of Free() Function

The syntax for the free() function for memory allocation in C is as follows:

Here is a list of difference between Malloc() Vs Calloc() in detail.

Conclusion

Programmers benefit largely from learning about dynamic memory allocation in C++ and C. Dynamic memory allocation can be used with the malloc() and calloc() library functions. Meanwhile, the free() method is useful for freeing up memory space.