Contiguous Allocation in Operating System

Memory management is a critical process within an operating system. When a program executes, it needs space in memory (RAM) for its data and instructions. Contiguous Allocation is one of the primary methods for allocating this memory. In contiguous allocation, a process or file is stored in a continuous, unbroken block of memory. The main goal is to ensure that the process or file is stored in a single, continuous memory block, which simplifies data access and can improve performance.

Contiguous Allocation is a memory allocation technique where a process or file is given a continuous block of memory. This means that when a process needs memory, it is assigned a contiguous memory area where the entire data or file is placed. All the memory blocks are adjacent to each other.

1. Fixed-size Partitioning: In this method, memory is divided into several blocks of a predetermined size. Each process is stored in one contiguous block. This method is simple but can lead to wasted memory (internal fragmentation) because small processes might be stored in large blocks.

2. Variable-size Partitioning: In this method, memory is divided into blocks of various sizes. When a process or file needs memory, a suitable block is allocated according to its size. This method is more flexible and makes better use of memory but can suffer from external fragmentation, where small, unused memory blocks are left scattered.

External fragmentation is a major problem. A solution is Compaction, a technique where all the small, unused memory blocks are combined to form one large block. Modern operating systems often use more advanced techniques like Paging and Segmentation to solve this problem, as they do not require contiguous allocation.