Virtual memory allows a program to use more memory than the physical RAM installed on a computer. It works by storing portions of programs and data that are not actively being used on the hard disk, freeing up RAM for active portions. This gives the illusion to the user and programs that they have access to more memory than is physically present. Virtual memory provides advantages like allowing more programs to run at once and not requiring additional RAM purchases, but can reduce performance due to the need to access the hard disk.

1. Virtual Memory
Submitted to: Submitted by:
Sir Asif Wagan F-16CS31

2. Content
 Virtual Memory
 Importance of Virtual Memory
 Without Virtual Memory
 With Virtual Memory
 Advantages and Disadvantages
 Address Space and Memory Space
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3. Virtual Memory
 Refers to something which appears to be present but actually it is not.
 The technique allows users to use more memory for a program than the real
memory of a computer.
 It is concept that gives the illusion to the user that they will have main memory
equal to the capacity of secondary storage media.
 It is alternate set of memory addresses.
 When the program is actually executed, the virtual addresses are converted
into real memory addresses.
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4. Importance of Virtual Memory
 If a computer running Windows requires more memory/ RAM then there is
installed in the system to run a program, etc.
 it uses a small section of the hard drive for this purpose. called virtual
memory technique.
 The program is stored in the secondary memory. The memory
management unit (MMU) transfers the currently needed part of the
program from the secondary memory to the main memory for execution.
 This to and fro movement of instructions and data (parts of a program)
between the main memory and the secondary memory is called
Swapping.
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5. Without Virtual Memory
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6. With Virtual Memory
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7. Advantages
 You can run more applications at
once.
 Allows you to fit many large
programs into a relatively small
RAM.
 You don't have to buy more
memory RAM.
 This concept is very helpful in
implementing multiprogramming
environment.
 Process need not be in memory
as a whole , Only part of a
program needs to be loaded into
memory.
Disadvantages
 Applications run slower if the
system is using virtual memory.
 It Takes more time to switch
between applications.
 Less hard drive space for your
use.
 It reduces system stability.
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8. Address space and Memory space
 Virtual address is the address used by the programmer
 the set of such addresses is called the address space or virtual memory.
 An address in main memory is called a location or physical address.
 The set of such locations in main memory is called the memory space or
physical memory.
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