This is an PPT of Operating System. It include the following topic "Unix Virtual Memory, Linux Virtual Memory & Virtual Memory using Segmentation ".

1. TOPIC:-UNIX VIRTUAL MEMORY,
LINUXVIRTUAL MEMORY &
VIRTUAL MEMORY USING SEGMENTATION
NAME:- TARUN TIWARI
ROLL NO.:- MCA/25007/18
CLASS:- MCA 2nd SEM.

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UNIX VIRTUAL MEMORY

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LINUX VIRTUAL MEMORY

4.  Memory – Management scheme that supports user view of memory
 A program is a collection of segments
• A segment is a logical unit such as:
 Main program
 Procedure
 Function
 Method
 Object
 Local variables, global variables
 Common block
 Stack
 Symbol table
 Arrays

5.  Logical address consists of a two tuple:
<segment-number, offset>,
 SEGMENT TABLE – maps two – dimensional physical addresses;
each table entry has:
-- BASE – contains the starting physical address where
the segments reside in memory
--LIMIT – specifies the length of the segment
 SEGMENT- TABLE BASE REGISTER (STBR) points to the segment
table’s location in memory
 SEGMENT- TABLE LENGTH REGISTER (STLR) indicates number of
segments used by a program;

6. Advantages of Segmentation –
 No Internal fragmentation.
 Segment Table consumes less space in comparison to Page table in paging.
Disadvantage of Segmentation –
 As processes are loaded and removed from the memory, the free memory space is broken
into little pieces, causing External fragmentation.

7. VIRTUAL ADDRESS SEGMENTATION
 Each process is divided into a number of segments, not all of
which are resident at any one point in time.

8. Example: Effective Address Calculation in Segmentation
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9. THANK YOU