What Is Buddy System in Data Structure?


Heather Bennett

The Buddy System is a widely used technique in the field of Data Structure. It plays a crucial role in memory management and allocation. In this article, we will explore what the Buddy System is and how it works.

What is the Buddy System?

The Buddy System is a memory allocation algorithm that divides memory into fixed-size blocks. These blocks are called buddies. Each buddy has a size that is a power of two, such as 2KB, 4KB, 8KB, etc.

The primary goal of the Buddy System is to efficiently manage memory by allocating and deallocating blocks as needed. It ensures that memory requests are fulfilled without fragmentation and maximizes memory utilization.

How does the Buddy System work?

The Buddy System works by dividing the available memory into power-of-two sized blocks. The smallest block size depends on the system’s page size, which is typically 4KB.

When a request for memory allocation comes in, the system searches for an available block with a size equal to or larger than the requested size. If such a block is found, it is allocated to fulfill the request.

If no suitable block is available, larger blocks are divided into two buddies with half their original size. One buddy is allocated for the request, and the other buddy remains free for future allocations.


Let’s say we have an initial block of 16KB (16384 bytes). When a request for 6KB comes in:

  • The system checks if there is an available block of exactly 6KB.
  • If there isn’t one, it looks for a larger block (in this case, 8KB).
  • If an 8KB block is found, it is divided into two buddies of 4KB each.
  • One buddy (4KB) is allocated for the request, and the other buddy (also 4KB) remains free for future allocations.

This process continues until a suitable block is found or the system runs out of memory.


When memory blocks are deallocated, the Buddy System checks if their buddies are also free. If so, the buddies are merged back into a larger block. This merging process continues until no more merging is possible.

Advantages of the Buddy System

The Buddy System offers several advantages:

  • Efficient Memory Utilization: The system ensures that memory blocks are allocated in powers of two sizes, reducing internal fragmentation and improving memory utilization.
  • Fast Allocation and Deallocation: Allocating and deallocating blocks in powers of two sizes allows for efficient searching and merging operations, resulting in fast allocation and deallocation processes.
  • Scalability: The Buddy System can easily scale with changing memory requirements by dynamically creating or merging blocks as needed.


The Buddy System is a powerful technique for managing memory allocation in Data Structures. By dividing memory into fixed-size blocks, it ensures efficient utilization while minimizing fragmentation. Its fast allocation and deallocation processes make it a popular choice in various computing systems.

The next time you encounter memory management challenges in your programming projects, consider implementing the Buddy System to optimize your application’s performance!

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