What are the different memory allocation techniques used in operating systems?

There are several memory allocation techniques used in operating systems, including:

1. Contiguous Memory Allocation: This technique divides the main memory into fixed-sized partitions and allocates each process to a specific partition. It can be further classified into two types: fixed partitioning and variable partitioning.

2. Paging: In this technique, the main memory is divided into fixed-sized blocks called pages, and the process is divided into fixed-sized blocks called frames. The pages of a process do not need to be contiguous in the main memory, allowing for efficient memory utilization.

3. Segmentation: This technique divides the process into logical segments, such as code segment, data segment, and stack segment. Each segment is allocated a variable amount of memory, and the segments can be located anywhere in the main memory.

4. Virtual Memory: Virtual memory is a technique that allows the execution of processes that are larger than the available physical memory. It uses a combination of main memory and secondary storage (usually a hard disk) to store and retrieve data as needed.

5. Demand Paging: This technique is a variation of virtual memory where pages are loaded into the main memory only when they are demanded by the executing process. It helps in reducing the initial memory requirement and improves overall system performance.

6. Swapping: Swapping is a technique where a process is temporarily moved out of the main memory and into secondary storage to free up memory for other processes. It is typically used when the available physical memory is insufficient to hold all the processes.

7. Buddy System: This technique involves dividing the main memory into fixed-sized blocks and allocating them in powers of two. When a process requests memory, the system searches for the smallest available block that can accommodate the requested size.

These memory allocation techniques are used by operating systems to efficiently manage and allocate memory resources to processes, ensuring optimal utilization and overall system performance.