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1. - Raj Mohan. B

2. Stores all kind of data and information

3. 1. Physical Memory- Total memory of the computer. EX: RAM
2. Logical Memory- CPU memory
3. Virtual memory- An imaginary memory area supported by
some operating systems (for example, Windows). It is an extension
of logical memory

4.  If the size of the program is greater than the available
memory size, then the concept of virtual memory is used
 Ever wondered how a 10GB Game like God Of War fits into
your 2GB RAM computer?

5.  Paging is a memory management technique in which the
memory is divided into fixed size pages.
 Paging is used for faster access to data.
 It is a logical concept

6. STATEMENT 1
STATEMENT 2
STATEMENT 3
STATEMENT 4
STATEMENT 5
STATEMENT 6
STATEMENT 7
Suppose a program X consists of 7
statements. But the memory can hold
only 4 statements, then Paging concept
is used.
PROGRAM X
STATEMENT 1
STATEMENT 2
STATEMENT 3
STATEMENT 4
STATEMENT 5
STATEMENT 6
STATEMENT 7

7.  Frames are physical concept
 It is present in the RAM
 We cannot see Pages, but we can see Frames

8.  Converting pages(virtual address) into frames (physical address)
 Enables program to be executed
 It is performed by the Memory Management Unit (M.M.U.)
CPU
(WHERE
PAGES ARE
DIVIDED)
MMU
Memory 1 Memory 2Virtual address
of
each page
Converts
virtual address
to physical
 If any error error occurs at
any physical address, it is
quickly retrieved from
memory and sent to the CPU

9. 0 0 0 0 0 1 0 1 1 1 0 1 1 1 0
6-bit page # 10-bit offset #
16-bit logical address
0 0 0 0 1 0 1
1 0 0 0 1 1 0
0 0 0 1 1 0 0 1 1 1 0 1 1 1 1 0
Page Table
16-bit Physical address

10.  LOGICAL ADDRESS
PAGE NUMBER
(WHICH PAGE IS TO BE
SEARCHED IN THE MEMORY)
PAGE OFFSET
(WHICH BYTE OF DATA IS TO
BE READ FROM THAT PAGE)
MAXIMUM OF 6 BYTES MAXIMUM OF 10
BYTES
 PHYSICAL ADDRESS
FRAME NUMBER FRAME OFFSET
MAXIMUM OF 6 BYTES MAXIMUM OF 10 BYTES

11. LOGICAL ADDRESS
PAGE P0
P1
P2
P3
P4
P5
P6
P7
MAPPING
PHYSICAL
ADDRESS
P7
P2
P1
P5
FO
F1
F2
F3

12. page
frame 0
page
frame 1
page
frame 2
page
frame 3
physical memory
offset
physical address
F3’s Value
F3
F2
F0
page table(MMU)
offset
logical address
P=3
CPU
P0
P1
P2
P3
P4
P5
P6
P7
F1

13. The paging process is protected by the concept of
insertion of an additional bit called VALID/INVALID
BIT
Consider a 14 bit address space= 2^14=16383
bytes
Let us set an address limit of 10468
If five process are defined within this address
space (P0-P4), it is considered as a Valid bit
Process P5 has started before 10468, so that alone
is considered
The remaining processes are considered as Invalid
In this way the pages are internally fragmented
This is how Paging is protected

15. • No external
Fragmentation
• Simple memory
management
algorithm
• Swapping is easy
(Equal sized Pages
and Page Frames)
• Internal
fragmentation
• Page tables may
consume more
memory.

16.  Segmentation is one of the most common ways to achieve memory
protection.
 Because internal fragmentation of pages takes place, the user’s view of
memory is lost
 The user will view the memory as a combination of segments
 In this type, memory addresses used are not contiguous
 Each memory segment is associated with a specific length and a set of
permissions.
 When a process tries to access the memory it is first checked to see
whether it has the required permission to access the particular memory
segment and whether it is within the length specified by that particular
memory segment.

17. 1
3
2
4
1
4
2
3
user space physical memory space
Free
Free

18.  Segment table - maps two-dimensional user defined address into one-
dimensional physical address
 base - starting physical address of the segment
 limit - length of segment
Logical Address space
Segment number
Offset
The maximum length of the offset value is 12 bits

19. Logical
Address
0<d<limit

21.  The advantage of segmentation is that the protection is associated
within the segments
 Sharing can be achieved by segments referencing multiple
processes
 Two processes that need to share access to a single segment would
have the same segment name and address in their segment tables

23.  No internal fragmentation
 Segment tables consume less
memory than page
 Lends itself to sharing data
among processes.
 Lends itself to protection.
Costly memory management
algorithm
As processes are loaded and
removed from memory , the
free memory space is
broken into little pieces
,causing external
fragmentation

25. In a combined
paging/segmentation
system a user’s address
space is broken up into
a number of segments.
Each segment is broken
up into a number of
fixed-sized pages which
are equal in length to a
main memory frame
Segmentation is
visible to the
programmer
Paging is transparent
to the programmer