OS QUIZ1 REV

Memory

is a fundamental resource of any

computing device, where it serves as storage and accessibility of data and instructions

memory management

In operating systems, _______________ is

another fundamental aspect of a computer system,where it ensures the efficient and effective use of a system's primary memory (RAM).

Main memory

also known as primary memory or random-access memory (RAM), is the main storage of computer systems that directly interacts with the CPU during the execution of the programs.

Main memory

It holds data and instructions temporarily and loses its data when the device power is interrupted.

Memory management

plays a vital role in modern operating systems, where it handles the gap between the limited memory space of the device and the demand of the user programs

Memory management

Where it involves handling the allocation, deallocation, and organization of data or instructions to ensure the optimization of computers memory resources.

Efficient Resource Utilization

optimize the memory usage to support multiprogramming.

Improved Performance

quick access to data and instructions.

System Stability

prevents crashes and memory conflicts.

Multitasking

enable to handle multiple applications.

Data Security

protects data integrity by restrictions to unauthorized access to every memory space.

Minimize Fragmentation Issues

to avoid unused memory space

Keep track of memory

monitor the status of memory space

Single-User Contiguous Scheme

▪Commercially available in 1940s and 1950s

▪ Entire program loaded into memory

▪Contiguous memory space allocated as needed

▪ Jobs processed sequentially

▪Memory manager performs minimal work

▪Registers is used to store the address

▪Accumulator is used to track program size

▪Disadvantages:

▪ No support for multiprogramming

▪ Not cost effective

▪Program size must be less than or equal to the

memory size to execute

Fixed Partitions

▪Commercially available in 1950s and 1960s

▪ It is also called static partitions

▪Main memory is partitioned

▪At system startup

▪One contiguous partition per job

▪Permits multiprogramming

▪Partition sizes remain static

▪Must shut down computer system to reconfigure

▪Requires:

▪Protection of the job’s memory space

▪Matching job size with partition size

first fit

partition scans the memory from top to bottom and allocates the job with the first suitable or empty block that is available or large enough to accommodate the job. As a result, it allots the first sufficiently huge hole.

best fit

assigns a job to the partition that is the smallest and most suitable of the free partitions that are available. In order to identify the smallest hole whose size is higher than or equal to the size of the process, it scans the whole list of holes.

next fit

partition is similar to the first fit; however, the scan will start from the location of the last assignment of job and check the next available or sufficient block.

worst-fit

partition assigns the jobs to the primary memory partition that has the biggest suitable size among all the free partitions. Contrary to the best-fit algorithm, it is to identify the biggest hole and assign it to be processed; it scans the complete list of holes.