A Case Study of Operating System, Assignments of Operating Systems

Download A Case Study of Operating System and more Assignments Operating Systems in PDF only on Docsity!

⦿ To facilitate easy,

efficient, fair, orderly,

and secure use of

resources

› Provide a user interface

› Organize files on disk

› Allocating resource to

different users with

security control

› Co-ordinate programs

to work with devices

and other programs

 Advantages over Windows

• It's almost free to relatively inexpensive
• Source code is included
• Bugs are fixed quickly and help is readily available through the vast support in Internet
• Linux is more stable than Windows
• Linux is truly multi-user and multi- tasking - multiuser: OS that can simultaneously serve a number of users - multitasking: OS that can simultaneously execute a number of programs
• Linux runs on equipment that other operating systems consider too underpowered, e.g. 386 systems, PDA, etc

⦿ Microsoft has made several

advancements and changes

that have made it a much

easier to use Operating

System, and although

arguably it may not be the

easiest Operating System, it is

still Easier thanLinux.

⦿ Because of the large amount

of Microsoft Windows users,

there is a much larger

selection of available software

programs, utilities, and games

for Windows.

 Disadvantages of linux

compared with Windows

• Isn't as popular as

Windows

• No one commercial

company is responsible for

Linux

• Linux is relatively hard to

install, learn and use

⦿ Hence currently, Linux is

mainly used in commercial

applications, server

implementation

Disadvantages of windows

⦿ Although Microsoft Windows

has made great

improvements in reliability

over the last few versions of

Windows, it still cannot match

the reliability ofLinux.

⦿ to viruses and other attacks.

Although Microsoft has made

great improvements over the

years with security on their

Operating System,

their Operating System

continues to be the most

vulnerable

⦿ Unlike a Windows operating system, Linux does not use drive letters. In Windows, you would address the floppy drive as A:, Windows system data is under C:, and so on. In Linux, all files and directories are located in a tree- like structure. The topmost directory is referred to as the file system root or just /. All other directories can be accessed from here. ⦿ The following is a short guide through the Linux file system tree, introducing the most important directories: ⦿ /home/ /home holds the private data of every user who has an account on your system. The files located here can only be modified by their owner or the system administrator. Your e-mail directory is located here, for example. ⦿ /media /media generally holds any type of drive except the hard drive of your system. Your USB flash drive appears under /media once you have connected it, as does your digital camera (if it uses USB) or your DVD or CD drive. As soon as the data source is disconnected (think of an USB flash drive or your camera), the respective directory under media is removed as well.

⦿ File management in windows can be done through Windows explorer or My Computer. Windows Explorer displays the hierarchical list of files, folders, and storage drives (both fixed and removable) on your computer. It also lists any network drives that have been mapped to as a drive letters on your computer. Windows Explorer can be used to copy, move, rename, and search for files and folders. For example, to copy a file, you can open a folder that contains the desired file to be copied or moved, and then just drag and drop the file to target folder or drive. Contents ⦿ 1 Using Windows Explorer ⦿ 2 Opening drives and folders ⦿ 3 View file details ⦿ 4 Copying and moving files using Explorer ⦿ 5 Create a new folder ⦿ 6 Rename a file or folder ⦿ 7 Delete a file or folder ⦿ When files or folders are deleted from hard disk, Windows places them in the Recycle Bin, from where they can be retrieved, until the Recycle Bin is made empty. Files or folders deleted from a ⦿ File Management in Windows ⦿ removable storage media such as network drive are permanently deleted and are not sent to the Recycle Bin.

• For a multitask system, multiple programs can be

executed simultaneously in the system

• When a program starts to execute, it becomes a

process

• The same program executing at two different times

will become two different processes

• A linux excutes it changes state depending upon the

circumstances

⦿ Running: A process will be in either running(current process in system)or ready to run(waiting to be assigned to system cpu) ⦿ Waiting:The process is waiting for a resource or event.Linux differentiates two types of waiting process; interputable and uninterputable.Interputable waiting process can be interputable by signals but are waiting directly on hardware conditions and cannot be interpated

⦿ A process contains its own independent virtual address space with both code and data, protected from other processes. Each process, in turn, contains one or more independently executing threads. A thread running within a process can execute application code, create new threads, create new independent processes, and manage communication and synchronization among the threads. ⦿ By creating and managing processes, applications can have multiple, concurrent tasks processing files, performing computations, or communicating with other networked systems. It is even possible to improve application performance by exploiting multiple CPU processors

⦿ Ready:May be scheduled for execution. The microkernel dispatcher keeps track of all ready threads and schedules them in priority order. ⦿ Standby:A standby thread has been selected to run next on a particular processor. The thread waits in this state until that processor is made available. If the standby thread's priority is high enough, the running thread on that processor may be preempted in favor of the standby thread. Otherwise, the standby thread waits until the running thread blocks orexhausts its time slice. ⦿ Running:Once the microkernel performs a thread or process switch, the standby thread enters the running state and begins execution and continues execution until it is preempted, exhausts its time slice, blocks, or terminates. In the first two cases, it goes back to the ready state

 Memory management

• Memory in a computer is divided into main memory (RAM) and secondary storage (usually refer to hard disk)
• Memory is small in capacity but fast in speed, and hard disk is vice versa
• Data that are not currently used should be saved to hard disk first, while data that are urgently needed should be retrieved and stored in RAM
• The mechanism is referred as memory management

⦿ The following is a list of address types used in Linux. ⦿ User virtual addresses :These are the regular addresses seen by user- space programs. User addresses are either 32 or 64 bits in length, depending on the underlying hardware architecture, and each process has its own virtual address space. ⦿ Physical addresses :The addresses used between the processor and the system's memory. Physical addresses are 32 - or 64 - bit quantities; even 32 - bit systems can use larger physical addresses in some situations. ⦿ Bus addresses :The addresses used between peripheral buses and memory. Often, they are the same as the physical addresses used by the processor, but that is not necessarily the case. Some architectures can provide an I/O memory management unit (IOMMU) that remaps addresses between a bus and main memory. An IOMMU can make life easier in a number of ways (making a buffer scattered in memory appear contiguous to the device, for example), but programming the IOMMU is an extra step that must be performed when setting up DMA operations. Bus addresses are highly architecture dependent, of course.

⦿ Each process on 32-bit Microsoft Windows has its own virtual address space that enables addressing up to 4 gigabytes of memory. Each process on 64 - bit Windows has a virtual address space of 8 terabytes. All threads of a process can access its virtual address space. However, threads cannot access memory that belongs to another process, which protects a process from being corrupted by another proces ⦿ Virtual Address Space ⦿ Memory Pools ⦿ Memory Performance Information ⦿ Virtual Memory Functions ⦿ Heap Functions ⦿ File Mapping ⦿ Large Memory Support ⦿ Global and Local Functions ⦿ Standard C Library Functions ⦿ Comparing Memory Allocation Methods