Memory allocation techniques in OS

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  Memory allocation techniques

Memory management
  • Memory is central to the operation of a computer system. It consists of a large array of words or bytes each with its own address. 
  • In uniprogramming system, main memory has two parts one for the operating system and another part is for the program currently being executed. 
  • In the multiprogramming system, the memory part of the user is further divided into accommodate processes. The task of the subdivision is cannot out by the operating system and is known as memory management.

Memory management techniques
The memory management techniques is divided into two parts...

Uniprogramming:
  • In the uniprogramming technique, the RAM is divided into two parts one part is for the resigning the operating system and other portion is for the user process. 
  • Here the fence register is used which contain the last address of the operating system parts. 
  • The operating system will compare the user data addresses with the fence register and if it is different that means the user is not entering in the OS area.
  •  Fence register is also called boundary register and is used to prevent a user from entering in the operating system area.
  •  Here the CPU utilization is very poor and hence multiprogramming is used.

Multiprogramming :- 
  • In the multiprogramming, the multiple users can share the memory simultaneously. 
  • By multiprogramming we mean there will be more than one process in the main memory and if the running process wants to wait for an event like I/O then instead of sitting ideal CPU will make a context switch and will pick another process.
  • Memory allocation techniques is used to increase the degree of multiprogramming and better utilisation of CPU .
  • In multiprogramming basically two types of memory allocation techniques.
     1. Contiguous memory allocation
       (A) fixed partition
       (B) variable partition 
     2. Non contiguous memory allocation.
        (A) paging
        (B) multilevel paging
        (C) inverted paging
        (D) segmentation
       (E) segmented paging
         
Thank you viewers.
This is published by soumy Sinha...

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