CTIS 155 – Information Technologies Icsevgi.bilkent.edu.tr/courses/ctis155/CTIS 155...
Transcript of CTIS 155 – Information Technologies Icsevgi.bilkent.edu.tr/courses/ctis155/CTIS 155...
System Software
System software includes ALL of the programs
needed to keep a computer + its peripheral
(çevre birim) devices running smoothly.
Same of the system software works behind thescene, some of it requires user guidence and control.
System Software has 2 major components
Operating Systems (OS)
System Utilities provide various maintenance functions
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System Software
The more you know about and understand the operating system, the better your computer will serve you.
Thus, it is NOT usual to set up/reinstall OSs so frequently.
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The Operating System (OS):
The operating system is a set of programs that perform certain basic functions with a specific type of computer.
Its most important role lies in coordinating the various functions of the computer’s hardware.
An operating system performs 5 basic functions. 1. starts the computer,
2. manages applications, (i.e., Application Software)
3. manages memory,
4. handles messages from input and output devices,
5. provides the user interface (i.e., GUI, CLI)
The OS is most often found on a hard disk.4CTIS 155 – Fall 2009-2010
Can you give an example of an OS that is NOT found on a hard disk?
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The Operating System (OS):
1. Function Starting the computer
When you start a computer, it loads the OS into the computer’s RAM. (To load = transfer something from a storage device to memory)
RAM is a form of temporary storage that is very fast, but that is volatile.
The process of loading the operating system to memory is called booting. 2 types of booting:
With a cold boot, you start a computer that is NOT already on.
With a warm boot, you restart a computer that is already on. Warm boots are often necessary after installing new software or after an application crashes or stops working.
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1. Function Starting the computer
Cold Boot
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Warm Boot
Ctrl+Alt+Del in Windows Sysems
or reset button
1. Function Starting the computer
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or +
The kernel is the central part of the OS that starts applications,
manages devices and memory and performs other essential functions.
Resides in memory at all times, so it must be kept as small as possible.
1. Function Starting the computer Cold/Warm
Boot
Step-by-Step Process
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BIOS is
loaded
Power-on
Self-test is
completed
Operating
System is
loaded
System
configuration
is
accomplishedSystem
Utilities are
loaded
Users are
authenticated
1. Function Starting the computer Cold/Warm
Boot
Step 1:the BIOS and setup program
When you first turn on or reset a PC, electricity flows from the power supply through the CPU, which resets and searches for the BIOS (basic input/output system) .
The BIOS is the part of the system software that equips the computer with the instructions needed to accept keyboard input and display information on the screen.
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1. Function Starting the computer Cold/Warm
Boot
The BIOS is encoded, or permanently written, in the computer’s ROM. ROM (read only memory), is a kind of memory that is nonvolatile.
Programs such as the BIOS that are encoded in ROM are meant to be reliably used over and over again.
BIOS screen: a text-only screen that provides information about the BIOS.
You can access the computer’s setup program by pressing a special key, such as Del or F8. The setup program includes settings that control the computer’s hardware.
You should NOT alter or change any of these settings unless you are instructed to do so.
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1. Function Starting the computer Cold/Warm
Boot
Step 2: The power on self test (POST)
After the BIOS instructions are loaded into memory, a series of tests are conducted to make sure that the computer and associated peripherals are operatingcorrectly. These tests are known as the POST.
Among the components tested are the computer’s main memory (RAM), keyboard, mouse, disk drives and hard disk.
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1. Function Starting the computer Cold/Warm
Boot
If any of the power-on self-tests fail, you will hear a beep, see an onscreen error message and the computer will stop.
You often correct such problems by making sure that components, such as keyboards, are plugged securely.
Some failures are so serious that the computer cannot display an error message; instead it sounds a certain number of beeps. If this happens, call for technical support. Write down any error message appear in the screen.
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1. Function Starting the computer Cold/Warm
Boot
Step 3: The operating system loads
Once the POST is successfully completed, the BIOS initiate a search for the operating system.
Options (or settings) in the setup program determine where the BIOS looks for the OS.
When the BIOS finds the operating system, it loads the operating system’s kernel into the memory. At that point, the OS takes control of the computer and begins loading system configuration
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1. Function Starting the computer Cold/Warm
Boot
Step 4: System Configuration
In Microsoft Windows, configuration information about installed peripherals and software is stored in a database called the registry. The registry also contains information about your system configuration choices, such as background graphics and mouse settings.
Once the operating system’s kernel has been loaded, it checks the system’s configuration to determine which drivers and other utility programs are needed.
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1. Function Starting the computer Cold/Warm
Boot
A driver is a utility program that makes a peripheral device function correctly.
If a peripheral device that is already installed on the system requires a driver to operate, that peripheral’s driver will be installed and loaded automatically. If the driver is missing, you may be prompted to insert a disk containing the needed driver.
Operating systems are equipped with Plug-and-Play (PnP) capabilities, which automatically detect new “PnP-compatible” peripherals that you may installed while the power was switched off, load the necessary drivers, and
check for conflicts with other devices. (i.e., USB, Firewire)
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1. Function Starting the computer Cold/Warm
Boot
Step 5: Loading System Utilities
Once the operating system has detected and configured all of the system’s hardware, it loads system utilities such as speaker volume control, antivirus software.
You can access additional “system configuration choices” in the Control Panel in MS Windows Systems.
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1. Function Starting the computer Cold/Warm
Boot
Step 6: Authenticating Users
When the operating system finishes loading, you may see a dialog box asking you to type a username and a password.
This process
authentication (or login), you verify that you are indeed the person who is authorized to use the computer.
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1. Function Starting the computer Cold/Warm
Boot
In OSs you can set up profiles. Associated with a username and optionally a password, a profile is a record of a specific user’s preferences for the desktop theme, icons and menu styles.
You can also enable other users to create and log on to their profiles, and they will see their preferences without disturbing yours.
On multi-user computer systems such as in a university lab, you must have an account to access a computer. Your account consists of your username and password and your storage space, which is called a home directory.
The account is usually created by the computer’s system administrator, the person who is responsible for managing the use of the computer in multi user systems.
At the end of this process, the user interface starts, enabling user interaction with computer programs.
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2. Function Managing Applications
When you start an application,
Application @ storage Application @ RAM
In the old days, single-tasking operating systems run one application program at a time.
You have to wait that application to be completed
Today, multi-tasking operating systems have the ability to run more than one application program at a time.
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2. Function Managing Applications
In multi-tasking, the computer does NOT actually run two applications at once, RATHER, it switches between them as need.
The satibility of an OS How it handles the multi-
tasking
Multitasking is accomplished by:
A foreground application – The active program or program in use
One or more background applications – Inactive program(s) or program(s) not in use
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2. Function Managing Applications
A better and a recent multitasking technique
Preemptive multitasking – Enables the operating system to regain control if an application stops working
Lose the unsaved data
But it prevents that the entire system would be down
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What is the access rate (speed) of a typical RAM (say DDR2) and a typical hard drive (say SATA disk)?
And compare them.
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The Operating System (OS):
3. Function Managing Memory
Computers use a temporary storage medium, called memory, to function as a buffer (tampon,
arabellek).
The OSs are responsible for managing memory.
The OS allocates memory areas for each running program; it keeps programs from interferingwith each other.
The OS uses virtual memory (VM), a method of using the computer’s hard disk as an extension of random access memory (RAM).
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3. Function Managing Memory Virtual Memory
In VM, program instructions & data are divided into units of fixed size called pages.
If memory is full, the OS starts storing copies of pages in a hard disk file called the swap file, which is a temporary storage space for bits & bytes.
When the pages are needed, they are copied back into memory. The transferring of files from storage to memory & back is called paging.
It is better to upgrade the computer’s RAM, because disks are slower than RAM so, paging slows down the computer.
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least recently
used data or
program instructions
page
swapped
out
swap
file
Virtual memory
management
hard disk
page
swapped
in
most recently
transferred data or
program instructions
memory
3. Function Managing Memory Virtual Memory
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In a Windows System, you can change the size of the paging files
4. Function Handling Input and Output
OS should handle input/output and enable communication with input/output devices. Most OS come with the drivers to for the most popular I/O devices.
If not, you can find the associated drivers within the box you purchased or the web sites.
I/O devices generate interrupts (signals, that tell the operating system that something has happened).
A key stroke or a movement of the mouse Interrupts
The OS provides interrupt handlers (mini-programs that are invoked when an interrupt occurs).
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4. Function Handling Input and Output
The communications between I/O devices and the CPU are handled by Interrupt request (IRQ) lines. Most PCs have 16 IRQs (from 0 to 15)
IRQ conflict may occur if two devices are configured to use the same IRQ
To remedy an IRQ conflict you may need to shut down the computer & remove peripheral devices, one by one, until you determine which one is causing the conflict.
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5. Function Providing the User Interface
The user interface is that part of the operating system with which the user/human interacts with a computer.
User interfaces helps you:
Start application programs
Manage disks and files,
Shut down the computer safely
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5. Function Providing the User Interface
Types of User Interfaces
1. Graphical User Interfaces (GUI)
2. Menu Driven
3. Command line (CLI)
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5. Function Providing the User Interface
Graphical user interface (GUI):
Uses graphics to create a desktop environment
Icons (small pictures) represent computer resources
Programs run within on-screen windows
You can give commands
Mouse clicks, drag-and-drop movements, pull-down menus, dialog boxes
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5. Function Providing the User Interface
Graphical user interface (GUI):
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4. Function Providing the User Interface
Command-line:
The user is required to type keywords or commandsin order to enter data or give instructions
You must observe complicated rules of syntax that specify exactly what you can type in a given place.
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4. Function Providing the User Interface
Menu-driven User Interface:
Text-based menus are used to show all of the options available to the user
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Exploring Popular Operating Systems
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WINDOWS XP
MAC OS XWINDOWS NT
WINDOWS CE
Microsoft Windows
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Windows 1.0 (1985)Windows 2.0 (1987)Windows 3.x (1990-1992)Windows NT (1993)Windows 95 (1995)Windows 98 (1998)Windows 2000 (2000)Windows ME (2000)Windows XP (2001)
Microsoft Windows XP
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Released in 2001 by Microsoft
XP is short for “experience”, reflecting Microsoft’s view that users want computers with rich audio and visual features.
Uses the same underlying code for all versions
Replaces all previous versions of Windows
Three versions:
Windows XP Home Edition
Windows XP Professional
Windows XP Server
Microsoft Windows NT
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Released in 1993 by Microsoft
Designed for client/server systems
2 components:
Windows NT Workstation
Designed for individual desktop computers.
Windows NT Server
Oriented to business needs
Offers
security,
remote administration,
directory services,
Web server
Microsoft Windows CE
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Light version of Windows for simplified versions of Office applications
For mobile Computing
Released in 1996 by Microsoft
Windows Embedded Compact
System used in PDAs or palmtops
Runs simplified versions of Windows programs
Data can be transferred to PCs
Includes handwriting and voice recognition
Mac OS
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Released in 1984
1st OS to use GUI
Easiest operating system for beginners
Could not be capitalized on its lead
@year 2000 Mac
OS X
UNIX
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Developed by AT&T in 1970s
Is a pioneering OS that continues to define what an OS should do & how it should work
Included first preemptive multitasking system, designed to work efficiently in a secure computer network.
Developed concepts of file management and path names
Facilitates client/server networking
Widely used by corporations
Lack of compatibility among the many different versions. It’s difficult to use.
Linux
Introduced by Linus Torvalds (Finnish Student) in 1991.
Expecting that Linux would be free alternative to UNIX.
Is then further developed by thousands of programmers.
Linux is open-source software
Powerful like UNIX
But free
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Linux
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Screenshot of Debian 5.0
System Utilities: Tools for Housekeeping
System utilities (=utility programs) are programs that help the operating system manage the computer system’s resources.
Keep the system running smoothly
Types of utilities:
Backup software
Antivirus software
File-searching software & File management
Disk scanning
Disk defragmentation
File compression
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Backup software
Includes programs that enable the user to copy data from the hard disk to another storage medium. If the hard disk fail, you can recover the data from the backup disk.
Types of backups:
Full backup: “a mirror image” is made of the entire hard disk’s contents
Incremental backup: the backup software copies only those files that have been createdor changed since the last backup occurred
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Backup software
Even if you do NOT have backup software, you can still make backup copies of your important files.
Assignments
Projects
Previously written code segments
etc
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Antivirus Software
Antivirus software protects the computer from computer viruses.
Such software uses a pattern-matchingtechnique that examines all of the files on a disk, looking for virus code “signatures”.
One limitation of antivirus software is that they can detect only those viruses whose “signatures” are in their databases
Most antivirus programs enable you to download the signatures of new viruses from the web site, if your system becomes infected by a virus that’s not in the system’s database, it may not be detected
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Antivirus Software
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Searching and Managing Files
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“My Computer” in Windows
“File Manager” in Mac OS X
Scanning and Cleanup
Disk-scanning utilities are programs that detect and fix physical and logical problemson storage devices.
Scanning programs look for a physical problem involving an irregularity on the disk’s surface that results in a bad sector, which is a portion of the disk that is unable to store data reliably.
The scanner can fix the problem by locking out the bad sector so that it’s no longer used.
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Scanning and Cleanup
Logical problems are usually caused by a power outage that occurs before the computer is able to finish writing the data to the disk.
Disk cleanup utilities are programs that remove files that are no longer needed.
In Windows Systems
Start Programs Accessories System Tools
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Disk defragmentation
As you use the computer, it creates & erases files on the hard disk. The result is that the disk is soon becomes a patchworkof files, with portions of files scattered here and there.
This slows disk access because the system must look in several locations to find all of a file’s segments
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Disk defragmentation
A disk defragmentation program moves data on a storage device to improve performance.
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A file compression utility
A file compression utility reduces the size of a file by as much as 80% without harming the data lossless
Compression enables faster downloads, but you must decompress a file after downloading it.
Most compression utilities can create archives, which is a single file stored in a special format.
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Data Compression Techniques:
1. Lossless and 2. Lossy compression
25.888888888
In a lossy system, using
25.[9]8 Interpreted as, "twenty five point 9 eights", the original string is perfectly recreated, just written in a smaller form.
In a lossy system, using
26 instead, the exact original data is lost, at the benefit of a smaller file size.
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System Update
Windows Update keeps the operating system up to date with any fixes or protections against external environment changes.
windowsupdate.microsoft.com
The updates will fix problems with the original version of the OS & will oftentimes provide protection against viruses and worms
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