Showing posts with label OPERATING SYSTEM. Show all posts
tic toc
SEB070007 TUTORIAL 5
Monday, September 15, 2008
4 TYPES OF DIRECT ACCESS STORAGE MEDIA
MAGNETIC DISKS
Description - use magnetic particles to store items such as data, instructions, and information on a disk's surface. Depending on how the magnetic particles are aligned, they represent either 0 bit or 1 bit. There are two types which are fixed head and movable head.
Examples- hard disks, floppy disks, removable cartridge.
Advantages- improves the media coercivity for a film structure, improve the thermal erasure problems related to a glass disk medium.
Image -
OPTICAL DISCS
Description- a type of storage media that consists of a flat, round, portable disc made of metal, plastic and lacquer that is written and read by laser.
Examples - CD-ROM, CD-R, CD-RW, DVD-ROM.
Advantages- store items in a single track that spirals from the center of the disc to the edge of the disc. Can read and/or write on one side only. Mass storage capacity, low cost per bit of storage, long media life.
Image-
FLASH MEMORY
Description - non-volatile computer memory that electrically erased and reprogrammed. For general storage and data transfer between computer and other digital products.
Examples- memory card, USB flash drives.
Advantages- non- volatile, fast read access time, better kinetic shock resistance than hard disks,
Image-
MAGNETO-OPTICAL DISKS
Description- a kind of optical disc drive capable of writting adn rewritting data. Consists of a ferromagnetic material seal beneath a plastic coating.
Advantages - makes the media extremely reliable, able to report any problem to the operating system.
Examples - hard disk drives for some operating system.
Image-
SEB070007- Amali 4
Friday, August 29, 2008
differencesS | ||
a page file is allocated on disk, does not used the memory mostly. leaving more RAM for actively used when an object is needed, it can be brought back into the memory. placed the file on seperate partition and Windows will remember it. unfortunately, this slows down the I/O due to the sleek time involved in switching back and forth between the two partition. |
| use a swap partition where the disk space allocated for paging is seperate from general data. this reduces the slowdown of the I/O. Linux uses a Least Recently Used (LRU) page aging technique to fairly choose pages which might be removed from the system. This scheme involves every page in the system having an age which changes as the page is accessed. The more that a page is accessed, the younger it is; the less that it is accessed the older and more stale it becomes. Old pages are good candidates for swapping. |
Windows uses structured exception handling to report page fault-based invalid accesses as access violation exceptions recent versions of Windows often report such problems with less technical error messages simply stating something along the lines of "this program must close" (an experienced user or programmer with access to debugger can still retrieve detailed information, if necessary). Additionally, recent Windows versions also write a minidump (similar in principle to acore dump) describing the state of the crashed process for later analysis alongside such less-technical error messages |
| UNIX (and UNIX-like) systems typically using signals,such as SIGSEGV, to report these error conditions to programs. UNIX and UNIX-like operating systems typically report these conditions to the user with error messages such as "segmentation violation", or "bus error" |
The page file in XP is a hidden file called pagefile.sys. It is regenerated at each boot — there is no need to include it in a backup. To see it you need to have Folder Options View set to ‘Show Hidden and System files’, and not to ‘Hide Protected mode System files’. | Page Sizes | The size of the block of pages examined is higher if the kernel swap daemon is intensively swapping; that is if the number of free pages in the system has fallen dangerously low. The blocks of pages are examined in a cyclical manner; a different block of pages is examined each time an attempt is made to shrink the memory map. This is known as the clock algorithm as, rather like the minute hand of a clock, the whole mem_map page vector is examined a few pages at a time. |
Trashing a file, if possible, is an atomic, constant time operation that will never error out due to out-of-space or other issue. Even trashing large files is instant, which is important because the user The out-of-space handling is importang, because it solves the "trashing files to make space on a full disk" problem that you have if you copy files to the trash. | Trashing | On non-unix system you see this strange .Trash-user directory On unix system the trash dir is hidden, and its not obvious that the media is not empty, because the connection with the files in |
http://lists.freedesktop.org/archives/xdg/2004-August/002923.html http://en.wikipedia.org/wiki/Comparison_of_Windows_and_Linux
SEB070007-Tutorial 3
Tuesday, August 5, 2008
- system that controls all the programs installed in a computer.It provides user-interface between users and the computer itself.
- It provides support for loading and execution of other application programs.
- It has system tools that monitor the computer performance, debug problems or maintain parts of the sytem.
- An operating system is like a resource manager. It contorls how processes to access resources.
- It protects applications from each other but yet share physical resources between them.
- It provides virtual machine such as virtual processor and share CPU.
- It also allocate and protect memory, enable virtual memory operations for application programs.
- It manages files by using filling system and divide up storage space.
- It organizes and control hardware and software so that it operates in predictable way.
- It manages the networking within the computer.
- It transforms the the physical world of devices, instructions, memory, and time into virtual world.
- It ensure the applications continue to run when the hardware updates and upgrades occur.
- It provides a consistent application interface, especially important if there is more than one of a particular type of computer using the operating system.
- The operating system provides a virtual proccessor to provide the illusion that a computer is doing more than one thing at a time.
- It provides device driver to that perform operations on behalf of programs for example input/output operations.
- It introduces new functions as it abstracts the hardware. As an example, it introduces file abstraction so that programs do not have to deal with discs.
- It can protects the system by controlling access to programs.
- It responsible towards secondary-storage management such as free-space management, disc scheduling and storage allocation.
- It keep tracks which part of memory are being used, allocate/deallocate memory space as required.
- It deals with hardware specific driver for devices and keep it all hidden from the rest of the system.
20 CORE FUNCTIONS OF OPERATING SYSTEM
SEB070007 TUTORIAL 2
Saturday, July 19, 2008
Application of software- subclass of computer that employs the capabilities of a computer directly to a task that the user wishes to perform.
Eg:- internet explorer
Communication of device- input device interact with computer. Eg:- keyboard, mouse, microphone
Computer- machine that manipulates data according to a list of instructions.
Dekstop computer- personal computer in a form intended for regular use at a single location as opposed to a mobile laptop.
Graphical User Interfaces- a type of user interface which allows people to interact with electronic devices. Graphical icons and visual indicators as opposed t0 text.
Hardware- physical components of a computer. Eg:- monitor, hard disk.
Internet- ascessible series or interconnected computer nnetworks that transmit data by packet switching using the standard Internet Protokol.
Installing- act of putting a program in a computer system to be run.
Network- interconnected group or system.
Eg:- internet explorer
Communication of device- input device interact with computer. Eg:- keyboard, mouse, microphone
Computer- machine that manipulates data according to a list of instructions.
Dekstop computer- personal computer in a form intended for regular use at a single location as opposed to a mobile laptop.
Embedded computer- a special purpose computer system designed to perform one or a few dedicated functions often with a real- time computing constraints. Eg:- traffic light, mp3 players.
Graphical User Interfaces- a type of user interface which allows people to interact with electronic devices. Graphical icons and visual indicators as opposed t0 text.
Hardware- physical components of a computer. Eg:- monitor, hard disk.
Internet- ascessible series or interconnected computer nnetworks that transmit data by packet switching using the standard Internet Protokol.
Installing- act of putting a program in a computer system to be run.
Network- interconnected group or system.
