about segmentation in operating system

1. PRESENTED BY
S.NANDHINI
I- M.sc(CS&IT)
NADAR SARASWATHI COLLEGE
OF ARTS & SCIENCE.
VADAPUDUPATTI , THENI.

2.  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.
 Local variable,global variable.

4.  Paging is transparent to the programmer.
 Paging eliminates external fragmentation.
 Segmentation is visible to the programmer.
 Segmentation allows for growing data
structures,modularity,and support for sharing
and protection.
 Each segment is broken into fixed –size pages.
 The segment entry points to a page table for that
segment.

7. o A method of using hard disk space to provide
extra memory.
o It simulates additional RAM.
o An address used by a programmer will be
called a virtual address ,and set such addresses
the address space.
o An address in main memory is called a location
or physical address and the set of such address
is called memory space.

9.  An operating system or os is a software
program that enables the computer hardware.
 To communicate and operate with the
computer software without a computer
operating system.
 A computer and software programs would be
useless.

10.  When to fetch the page from auxiliary memory to
main memory.
 2 Approaches:
 Demand paging only brings pages into
main memory when a reference is made to a
location on the page.
 Prepaging brings in pages whose use is
anticipated.

11.  Not all pages in main memory can be
selected for replacement.
 Some frames are locked(cannot be
paged out)

12. Resident set:.
Set of a process pages which are
in main memory.
Os must manage the size and
allocation policies which effect the
resident set.