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This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. The program is loaded in the main memory for the program to run efficiently. OS tracks the main memory usage by each application. Also, OS decides which memory should be allocated to which program and how much memory should be allocated and how many users must be given access to check the memory status.
OS does the process scheduling. It decides the time of each process assigned to the processor and the order in which the processor is accessed. All the activities of process management are done by OS. It also tracks the status of all the processes. This program is done by the traffic controller. When the process is not required, the processor is de-allocated by OS.
OS does device management easily. Device communication is carried out with the help of drivers. The devices connected to the system are tracked and monitored well. The access to the device by the programs and the time duration is decided by OS. OS organizes the file system into directories so that the files can be easily searched and used whenever needed. The directories have other directories and other files.
Information regarding the files, user access details and settings and the running status of each file is monitored and logged by OS. This helps the user to check the files and provide details of the files by checking the logs and the time duration. OS is also called the file system due to the file management provided by OS. OS checks whether the system is ready to work. If not, the system is rebooted and OS makes the system work.
This is done by shutting down all the applications so that the application that uses most storage is closed. This helps the user to decide the applications for their use and when the system reboots, the application takes less space.
Booting also helps to install and start newly installed software and to work based on customer needs. It takes time to load the program into the system. Worst fit:- In the worst fit, allocate the largest available hole to process. This method produces the largest leftover hole. Inefficient memory utilization is a major issue in the worst fit. Fragmentation: A Fragmentation is defined as when the process is loaded and removed after execution from memory, it creates a small free hole.
These holes can not be assigned to new processes because holes are not combined or do not fulfill the memory requirement of the process. To achieve a degree of multiprogramming, we must reduce the waste of memory or fragmentation problem. In operating system two types of fragmentation: Internal fragmentation:. Internal fragmentation occurs when memory blocks are allocated to the process more than their requested size.
Due to this some unused space is leftover and creates an internal fragmentation problem. Example: Suppose there is a fixed partitioning is used for memory allocation and the different size of block 3MB, 6MB, and 7MB space in memory. Now a new process p4 of size 2MB comes and demand for the block of memory. It gets a memory block of 3MB but 1MB block memory is a waste, and it can not be allocated to other processes too.
This is called internal fragmentation. External fragmentation: In external fragmentation, we have a free memory block, but we can not assign it to process because blocks are not contiguous. After allocating process p1 process and p2 process left 1MB and 2MB. Suppose a new process p4 comes and demands a 3MB block of memory, which is available, but we can not assign it because free memory space is not contiguous. This is called external fragmentation.
Both the first fit and best-fit systems for memory allocation affected by external fragmentation. To overcome the external fragmentation problem Compaction is used. In the compaction technique, all free memory space combines and makes one large block. So, this space can be used by other processes effectively. Another possible solution to the external fragmentation is to allow the logical address space of the processes to be noncontiguous, thus permit a process to be allocated physical memory where ever the latter is available.
Paging: Paging is a memory management scheme that eliminates the need for contiguous allocation of physical memory. This scheme permits the physical address space of a process to be non-contiguous. Skip to content. Change Language. Related Articles.
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