FOR FREE CONTENT
- Introduction: OS
- Booting Process
- Command Interpreter
- Dual mode of operation
- System Calls
- Difference between system call and library call
- Interrupt and Trap
- Introduction
- Scheduling Criteria, Terms and Concepts
- Different Type Scheduling Algorithms
- Longest Job First
- Longest Remaining Time First
- Highest Response Ratio Next (HRRN)
- Priority Scheduling
- Least Completed Next (LCN) Scheduling
- Multi-Level Queue Scheduling
- Multilevel Feedback Queue Scheduling
- Guaranteed Scheduling
- Fair Share Scheduling
- Lottery Scheduling
- Multi-Processor Scheduling
- Deadline Scheduling
- Rate-Monotonic Scheduling
- POSIX Real-Time Scheduling
- Priority Inversion
- Proportional Share Scheduling
- Comparison table of Scheduling Algorithm
- Algorithm Evaluation for Scheduling
- Important concept of MM
- Memory Representation as Address
- Memory layout for a Process
- Logical and Physical Address Space
- Necessity of Memory Management
- Introduction
- Concept of Non-contiguous memory allocation
- Basic concept of Paging
- Address Translation
- Process of Paging Method
- Calculation of Offset for paging
- Calculation of Logical Address Bit and number of Pages
- Calculation of Physical Address Bit and number of Frames
- Calculation of Page Table Size
- Organization of MMU
- Why Page size power of 2
- Paging Address Calculation: example1
- Paging Numeric Problem: Example2
- Paging Address Calculation: Example3
- Paging Address Calculation: Question1
- Some Important Question 2
- Paging Address Translation: Question3
- UGC NET Paging Question
- GATE Paging Question
- Number of information at Page Entry
- Exams Question on Page Entry Information
- Exam Question: Page Entry Information
- Calculates Page Table Entry Size
- Calculates Page Size
- Calculation of Optimal Page Size
- Question on Optimal Page Size
- Hashed Page Table with Example
- Inverted Page Table with Gate Question
- Question on Inverted Page Table
- Multi-Level Paging
- Multi-level paging: Example1
- Multi-level paging: Example2
- Allocation of Frames
- Subject Mock
Number of information at Page Entry
As we discussed earlier that page entry not only contains frame numbers, it also contains some important information.
Frame number:
As we know frame number is the most important information in page entry and by which we can get actual address memory of target data.
Reference Bit:
Reference bit is important at the time of page replacement algorithm. It is used to identify how many times this page is referred at the time of execution that helps to know when the last time this page is referred.
Cache Disabled:
To make mapping fast some pages are kept at cache which is called write through cache. But sometimes we are not willing to access cache; we directly access RAM to get the data, especially when we are currently working with fresh data. In this case, we disabled the cache.
Dirty Bit or Modified Bit:
This information shows that a certain page is modified or not at the time of execution. Like dirty bit 0 means page is not modified and dirty bit 1 means page is modified.
This information requires at the time of page replacement when the page will replace then modified information should also keep in secondary memory.
This bit also helps to protect memory from invalid memory addresses. When this bit is set to valid, the associated page is in the process’s logical address space and is thus a legal (or valid) page. When the bit is set to invalid, the page is not in the process’s logical address space. Illegal addresses are trapped by the use of the valid–invalid bit.
Valid / Invalid bit:
This bit is also called a present or absent bit. This information identified a certain page is currently present in the main memory or not.
Valid (1): Page is present in main memory and Invalid (0): Page is not present in main memory.
This concept is coming when we load the pages in the main memory as per requirement, then this bit is required to check.
Permission Bit:
This information is required for the protection and security of pages by access authorization like read, write, or execution permission.
