This document discusses different approaches to memory management in computer systems. It explains that memory plays a central role, with the CPU and I/O system interacting with memory. It then describes four approaches to memory allocation and management: contiguous storage allocation, non-contiguous storage allocation, virtual storage using paging, and virtual storage using segmentation. Paging divides memory into fixed-size frames and logical memory into same-sized pages, using a page table to map logical to physical addresses. Segmentation divides a program into variable-sized segments and uses a segment table to map two-dimensional physical addresses. The most efficient approach sometimes combines paging and segmentation.

1. STORAGE MANAGEMENT
IN THIS POWERPOINT I AM GONNA TELL YOU, HOW MEMORY PLAYS A
CENTRAL ROLE IN A COMPUTER SYSTEM?
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2. FLOW OF MEMORY!!!
• In a working of a modern systems memory plays a central role,
as shown in a flow chart:-
• Both CPU and I/O system interacts with memory.
CPU Memory
I/O
System
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3. WHAT IS MEMORY?
• Memory is a large array of words or bytes, each with its own
address.
• The CPU reads from and writes to specific memory address.
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4. MEMORY EXECUTION
• For execution a program must be assigned some memory area
and loaded into memory in order to be executed.
• As the program executes, it accesses program instructions and
data from memory by generating addresses of the allocated
memory.
• When the program terminates, its memory space is declared
free, and the next program may be given the same memory
area.
• Now, there can be many user programs loaded in the memory
along with system programs and operating system.
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5. THEN, HOW IS MEMORY MANAGED IN SUCH
A SITUATION?
Different approach to a memory allocation and its management
are with its relative effectiveness:-
1. Contiguous Storage Allocation.
2. Non Contiguous Storage Allocation.
3. Virtual Storage using Paging.
4. Virtual Storage using Segmentation.
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6. 1.CONTIGUOUS STORAGE ALLOCATION.
• Each problem, which is to be executed ,is allocated a
contiguous storage memory.
• Each job step is considered as a single independent entity for
allocation of a contiguous storage area.
• At every job step initiation, the OS has to ensure that sufficient
contiguous area is available to accommodate it.
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7. • logical Physical
• address address
CPU
Yes
/N
o
Limit
register
+
Relocation
Register
Memor
y
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8. 2.NON CONTIGUOUS STORAGE
ALLOCATION.
• A program can be stored in non contiguous memory areas.
• Here, a program is divided into smaller components of equal sizes.
One of more components can be stored in the non contiguous
memory areas.
• Each component in the particular memory area is provided addresses
0,1,2..n.
• Now a program can be stored at non contiguous locations, but what
if we use all available free memory is still the program can not be
loaded into the main storage because the total free memory is still
less than the size of the program.
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9. NOW THE PROBLEM MENTIONED IN LAST POINT ,
HOW TO OVERCOME THAT PROBLEM?
• To solve such a problem we require a technique with which a
program can still be executed even if all of its is not loaded in a
memory.
• Solution is . They are of 2 types namely:
• Program Paging
• Program Segmentation
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10. • Divide physical memory into fixed-sized (power of 2) blocks called
frames.
• Divide logical memory into blocks of same size called pages.
• Keep track of all free frames.
• To run a program of size n pages, need to find n free frames and load
program.
• Page table : used to translate logical to physical addresses.
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11. • Now when a required page is not in the main storage an interrupt is
known as missing page interrupt, is raised.
• This fault is commonly called as page fault.
• The OS takes action by bringing required page from the secondary
storage into an empty page block, this is called demand paging or
page in.
• After page in page table is modified and new physical address is
stored in it and execution resumes.
• In some cases now storage is left then storage block is vacated by
process page out.
• This reading and writing of pages determines page traffic.If page
traffic is too much situation is called thrashing.
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12. • Memory-management scheme that supports user view of memory.
• A program is a collection of segments. A segment can be any logical unit
eg: code, global variables, heap, stack,...
• Segment sizes may be different
• Segmentation Architecture:-
• Segment table– maps two-dimensional physical addresses; each table entry
has:
1.base – contains the starting physical address where the segments
reside in memory.
2.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
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13. • In the same way as of paging, segment in the memory are processed
and if a segment is not available in the memory segment missing
fault is raised.
• To increase the efficiency of a system sometimes paging and
segmentation is combined. A large segmentation is broken into
pages and is stored in contiguous area.
• Now within the pages `swapping’ is possible as it improves the
efficiency of system as access of pages within the segment is
fastened up.
• Thus the address now contains the segment id, page number within
the segment and the word in a page.
• OS like IBM 360/67 and MULTICS use this very technique
segmentation with paging.
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14. THANK YOU
A Presentation By- ATUL SHARMA
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