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Top 10 List of Week 04

In this Top 10 list, I will give what materials I have learned during week 4 at my Operating System course. In each of the points I stated, there is a clickable link that will take you to the website I learned the material from, my thoughts and review of the page itself, and a short summary of the material.

One Logical Address

An address generated by the CPU is a logical address whereas address actually available on memory unit is a physical address. Logical address is also known a Virtual address

In other words, the operating system or some other programs uses base addresses as a measure to find addresses. Here base address means starting address of a memory block. According to the program written the CPU generates a address.This address is added with the base address so that it forms the physical address.Here in this case the address generated by the CPU is called as Logical Address.

Two Physical Address

In computing, a physical address (also real address, or binary address), is a memory address that is represented in the form of a binary number on the address bus circuitry in order to enable the data bus to access a particular storage cell of main memory, or a register of memory mapped I/O device.

Three Differences Between Logical and Physical Address in Operating System

• The basic difference between Logical and physical address is that Logical address is generated by CPU in perspective of a program whereas the physical address is a location that exists in the memory unit.

• Logical Address Space is the set of all logical addresses generated by CPU for a program whereas the set of all physical address mapped to corresponding logical addresses is called Physical Address Space.

• The logical address does not exist physically in the memory whereas physical address is a location in the memory that can be accessed physically.

• Identical logical addresses are generated by Compile-time and Load time address binding methods whereas they differs from each other in run-time address binding method. Please refer this for details.

• The logical address is generated by the CPU while the program is running whereas the physical address is computed by the Memory Management Unit (MMU).

Four Address Space

An address space is a range of valid addresses in memory that are available for a program or process.

Address space is the amount of memory allocated for all possible addresses for a computational entity, such as a device, a file, a server, or a networked computer. Address space may refer to a range of either physical or virtual addresses accessible to a processor or reserved for a process.

Five Memory Allocation

Memory allocation is the process of setting aside sections of memory in a program to be used to store variables, and instances of structures and classes. There are two basic types of memory allocation:

• Static Memory Allocation : Declaration of variables, structures, and classes at the beginning of a class or function. When you declare a variable or an instance of a structure or class. The memory for that object is allocated by the operating system. The name you declare for the object can then be used to access that block of memory.

• Dynamic Memory Allocation : When you use dynamic memory allocation you have the operating system designate a block of memory of the appropriate size while the program is running. This is done either with the new operator or with a call to the malloc function. The block of memory is allocated and a pointer to the block is returned. This is then stored in a pointer to the appropriate data type.

Six Memory Management Unit

A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passed through itself, primarily performing the translation of virtual memory addresses to physical addresses.

An MMU effectively performs virtual memory management, handling at the same time memory protection, cache control, bus arbitration and, in simpler computer architectures (especially 8-bit systems), bank switching.

Seven Address Binding

Address binding is the process of mapping from one address space to another address space. Logical address is address generated by CPU during execution whereas Physical Address refers to location in memory unit(the one that is loaded into memory).Note that user deals with only logical address(Virtual address).

Eight Big and Little Endian

• Big Endian Byte Order: The most significant byte (the “big end”) of the data is placed at the byte with the lowest address. The rest of the data is placed in order in the next three bytes in memory.

• Little Endian Byte Order: The least significant byte (the “little end”) of the data is placed at the byte with the lowest address. The rest of the data is placed in order in the next three bytes in memory.

Nine Updating VirtualBox

When you perform a system update with the update manager, Virtualbox updates will appear.

You can also get the same effect by doing it through the terminal:

sudo apt-get update

sudo apt-get upgrade

This will provide you with the latest version of Virtualbox. This however, will not keep your Virtualbox Extension Pack updated. Packages will only be updated when you open Virtualbox. You will immediately get a notification that there is an update for virtualbox or an update for the Extension Pack. Note that an extension pack is required if you want proper support for sharing between host and guest, 3D support, USB support, and more.

Ten The Fastest Operating System

Chromium OS is an open-source project that aims to build an operating system that provides a fast, simple, and more secure computing experience for people who spend most of their time on the web. Many people refer Chromium as the fastest Operating System you could use.