OS

Page Table

Most OS allocate a page table for each process. A pointer to the page table is stored in the PCB of the process. When the dispatcher start a process, it must reload the user registers and define the correct hardware page table from the stored user page-table. The hardware page table can be implemented in …

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Memory Mapping Schemes

Memory mapping is a technique to bind user-generated addresses to physical addresses in the memory. This requires static binding or dynamic binding. CPU gets instruction from memory, and then decode the instruction during the instruction-execution cycle. The instruction also contains the memory address of operands that need to be fetched. The CPU finished the instruction …

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Storage Structure

Files are stored on random-access storage devices including hard disks, optical disks, and solid-state disks. The storage device can entirely be used as a file system or divided into many partitions. Each partition may or may not have a different file system. Storage devices are collected into RAID sets, that provides high availability and fault …

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File Type

The operating system should support the file system. If the OS does not recognize a file type then any operation on the file will not be successful. The files are given an extension to indicate the type of file separated by a period or a dot. For example, finance.java – A java program source code …

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File Concepts

To a user, the file is the smallest unit of storage on a computer system. The user performs file operations such as open, close, read, write and modify. They can create or delete files from the system. In this article, you will learn the basics of file and file system. File Concept Computer store information …

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Paging

Paging allows the physical address space of a process to be non-contiguous. It avoids the external fragmentation andthere is no need for compaction. Fragmentation problem affects the backing store (disk) of the main memory where processes are swapped in or out.The compaction is not possible due to the slow access speed of the backing store. …

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Logical Memory Address vs. Physical Memory Address

The memory binding could be static or dynamic. In dynamic binding system, user-generated virtual addresses are mapped to physical addresses. This leads to better memory utilization. The address generated by CPU is called a logical address, and the address seen by the memory unit is called a physical address. The physical address is loaded into …

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What is a Deadlock?

In a multiprocessing environment, several processes compete for limited resources. A running process goes to waiting state when a resource is not available. The process could not change its state because some other process holds the resources. This is called a deadlock. The operating system does not provide with deadlock prevention mechanism, the programmers must …

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