When a process needs to execute, memory is requested by the process. What is difference between continuous and contiguous? Continuous: Continuing in time or space without interruption. Contiguous: means neighboring, close to each other or connected in space or time.
You can say having a common boundary or edge; abutting; touching. What causes a page fault? Page Fault. A page fault occurs when a program attempts to access a block of memory that is not stored in the physical memory, or RAM. However, an invalid page fault may cause a program to hang or crash. This type of page fault may occur when a program tries to access a memory address that does not exist.
What is single contiguous allocation? Single Contiguous Memory Allocation is a simple memory allocation scheme, which requires no special hardware features. Entire available memory is allocated to a single job. In this scheme of allocation, the main memory is divided into 3 contiguous regions. One portion is permanently allocated to the operating system. What are the disadvantages of contiguous memory allocation? Advantages and Disadvantages The main disadvantage of contiguous memory allocation is memory wastage and inflexibility.
As the memory is allocated to a file or a process keeping in mind that it will grow during the run. The directory entry of a file contains a pointer to the first block and a pointer to the last block. Hence, the index block of an indexed allocation plays the same role as the page table. Index allocation supports both sequential and direct access without external fragmentation. The indexed allocation suffers from wasted space. The index block may not be fully used i. The number of entries of an index table determines the size of a file.
To overcome this problem, we can have multiple index blocks and chain them into a linked list. Step 2: Let n be the size of the buffer. Step 3: check if there are any producer. Step 4: if yes check whether the buffer is full. Step 5: If no the producer item is stored in the buffer. Step 6: If the buffer is full the producer has to wait. Step 7: Check there is any consumer. If yes check whether the buffer is empty. Step 8: If no the consumer consumes them from the buffer. Step 9: If the buffer is empty, the consumer has to wait.
The value of the end is It means the allocation is finished on the 25 th block. We can see in the below figure that the block 25 comprised of -1, which means a null pointer, and it will not point to another block. The Indexed allocation method is another method that is used for file allocation.
In the index allocation method, we have an additional block, and that block is known as the index block. For each file, there is an individual index block.
In the index block, the ith entry holds the disk address of the ith file block. We can see in the below figure that the directory entry comprises of the address of the index block. An Inode is a block that is created at the time when the file system is designed. Join YouTube Channel. File Allocation Methods There are different kinds of methods that are used to allocate disk space.
There are various types of file allocations method: Contiguous allocation Extents Linked allocation Clustering FAT Indexed allocation Linked Indexed allocation Multilevel Indexed allocation Inode There are different types of file allocation methods, but we mainly use three types of file allocation methods: Contiguous allocation Linked list allocation Indexed allocation These methods provide quick access to the file blocks and also the utilization of disk space in an efficient manner.
Example of contiguous allocation We can see in the given diagram, that there is a file. Advantages of Contiguous Allocation The advantages of contiguous allocation are: The contiguous allocation method gives excellent read performance. Contiguous allocation is easy to implement. The contiguous allocation method supports both types of file access methods that are sequential access and direct access. The Contiguous allocation method is fast because, in this method number of seeks is less due to the contiguous allocation of file blocks.
Disadvantages of Contiguous allocation The disadvantages of contiguous allocation method are: In the contiguous allocation method, sometimes disk can be fragmented. In this method, it is difficult to increase the size of the file due to the availability of the contiguous memory block.
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