Question

Name three memory management techniques and describe the general approach taken in each.

Short answer

Paging, segmentation, and virtual memory are three memory management techniques that involve dividing memory into units, logical segments, and extending with storage, respectively.

Step-by-step solution

Understanding Memory Management

Memory management is the process of controlling and coordinating computer memory, assigning portions to various running programs to optimize overall system performance. It involves techniques that ensure efficient allocation, use, and release of memory resources.

Paging Technique

Paging is a memory management technique where the operating system divides the memory into fixed-sized units called 'pages.' Each process is split into pages as well, which are loaded into any available memory frames. This technique allows efficient and flexible use of memory, as pages can be moved between main memory and storage, resulting in non-contiguous memory allocation.

Segmentation Technique

Segmentation is another memory management technique where memory is divided into different segments based on the logical divisions of a program. Each segment represents a different logical unit, like a function or an array, which allows programmers to organize memory in a way that is similar to their logical view of data. Segmentation helps in providing better access and control by allowing the user to allocate memory in a dynamic manner.

Virtual Memory Technique

Virtual memory is a technique where secondary storage (like a hard disk) is used to extend the apparent size of the working memory—a computer uses storage to simulate additional RAM. The system keeps track of available memory space in both primary and secondary storage, automatically shifting data between them to provide an illusion of a large main memory space, thus making the memory management transparent to applications.

Key concepts

Paging

Paging is a memory management technique used by operating systems to help manage memory efficiently. In this system, both the physical memory and the processes within the system are divided into small fixed-size blocks known as 'pages'. Each page holds a part of the program's instructions and data.
When a process is executed, its pages are loaded into available memory frames, which are fixed-size blocks of physical memory. This allows for a flexible allocation of memory without requiring contiguous blocks. Each page can reside in any memory frame, providing flexibility. In addition, because pages are fixed in size, the issue of fragmentation is minimized. This means memory can be used more effectively.
With paging, the operating system keeps track of all pages via a page table. It maps each virtual page to a physical memory frame, ensuring the correct pages are in memory when needed. This process occurs seamlessly, allowing programs to run smoothly without being aware of the underlying structure. Paging is fundamental to creating an efficient, flexible memory management system without the need for programs to allocate memory in successive banks.

Segmentation

Segmentation is another effective memory management technique, differing from paging by dividing memory based on the logical view of a program rather than a strictly fixed size. It aligns closely with how developers naturally think of their software, making it very user-friendly.
Each 'segment' in segmentation represents a logical unit or part of a program, like functions, arrays, or data structures. A program may have several segments, each with a different length corresponding to the logical requirement of that unit. This provides advantages in terms of organization and memory use, as memory can be allocated dynamically, closely matching the program's needs.
Segmentation allows programmers to work with logical address space, resulting in more intuitive memory management. These logical addresses are then transformed into physical addresses by the system during execution, adapting to the required program logic. This setup can also ease the process of code sharing and protection, as specific segments can be adjusted or protected independently, offering robust control over memory utilization.

Virtual Memory

Virtual memory is an advanced memory management technique that creates the illusion of a large main memory through the use of both primary memory (RAM) and secondary storage (like a hard drive). This means programs can run as if the system has more memory than physically available, overcoming size limitations.
The core concept of virtual memory involves mapping virtual addresses to physical addresses. When systems run multiple applications or when large programs exceed the actual physical memory available, secondary storage is used to hold parts of the data or code not actively in use. This setup allows the computer to run larger applications and multitask more effectively, as it effectively "swaps" data between RAM and disk storage.
Virtual memory is managed by the operating system, which automatically handles data exchange between memory and storage without any manual intervention from the user or running applications. This transparency simplifies memory management for users while maintaining high performance and efficient memory use. With virtual memory, systems can optimize processes to run efficiently, even under high demand or with constrained physical resources.