1. System Software
CSCI 101

2. System Software
Provides the tools and the environment in which application software can be created and run. (CSI)
Consists of:
Operating System (OS), &
Utility Programs

3. What is an Operating System
An operating system is computer software which controls the standard functions of a computer.
Below, is an example of the Windows 10 operating system.

4. What does the OS do? The Operating System Provides a User Interface
Manages memory and storage
Manages the CPU
The Operating System
Manages computer hardware and peripherals
Provides a consistent interaction between applications and the CPU

5. Layers of a Computer System
The Operating system is the intermediary between the applications you use (e.g. MS Word) and the Hardware (CPU)
USER
Applications
Operating System
Other System Software
Computer Hardware
CPU, ROM, Main Memory, System bus

6. The User Interface
Provides a means for the user to interact with their computer. we have both command line and graphical user interfaces.
Command Line: All user instructions to the computer and typed
Graphical: User interfaces with a graphical screen, clicking, dragging,…

7. Process
Each time user input occurs, or a command from an application, e.g. a keystroke, or play on a movie, an process is generated
This process is sent to the OS, indicating that a set of instructions should be executed to make the output from this process occur.

8. Process Execution The process are fed into the CPU
The CPU stores the set of the processes in the queue
Then it executes the processes in order of importance, and based on which came in first
Process Queue
CPU A
Click
Scroll
Open Word

9. Round Robin
The most widely used method of process executing is a Round Robin.
Here each process in the queue gets executed for a short period of time (time slice), then they each take turns until processes complete

10. Interrupt
When an event is of high importance. E.g. a Skype call is coming in, it singles an interrupt
Interrupts tell the OS that this event is in need of immediate attention and it’s event gets put to the top of the priority, and will be executed quickly
Event Queue
CPU A
Click
Scroll
Open Word
Skype
Call

11. Uniprogramming
Processor must wait for input/output operations to execute before proceeding.
E.g. While the computer is waiting for the user to enter the next letter, nothing happens.

12. MultiTasking
When one job needs to wait for I/O the CPU can process events from another job.

13. Memory Management
The OS uses the RAM to store data and instructions that are needed by the CPU to perform tasks.
The programs that are currently running are stored in memory

14. Physical Addresses
Is the actual address of the program or data in main memory (CSI)
Main Memory is broken up into addresses of size 8, 16, and 32 bits 1 2 3 4 5 6 7
Data

15. Partition Memory Management
The operating system is responsible for making sure that one program cannot access another's memory.

16. Running out of RAM
If you are trying to run applications that require more RAM than your computer has available you can run out.
In this situation the CPU borrow memory from the Hard Disk to work as Virtual Memory.
The Hard Disk takes longer to access data than the RAM so ideally you don’t want to use Virtual Memory

17. Accessing Memory Main Memory RAM CPU Virtual Memory ROM Memory
Disk Storage
ROM Memory

18. Running out of Virtual Memory
The Hard Disk only allocates a certain amount of space for virtual memory.
When this space runs out you experience Thrashing, and your computer becomes sluggish
In this situation you can add more RAM to your computer, or buy a new computer

19. Virtual Memory Terms
Memory borrowed from the hard drive to serve as RAM. Swap File: File on hard drive storing copies of RAM Paging: Retrieve copies of RAM from the hard drive Trashing: Repeatedly going back and forth between RAM and swap file.

20. Managing Storage
The Operating System keeps track of the names and locations of all the files you save along with the applications that you install

21. Manages Computer Hardware and Peripherals
The operating system communicates to the peripherals either through device or via plug and play.
Device Drivers: Facilitate communication between the Operating system and the device
Plug and Play: Included in the operating system for standard peripherals, basically the driver is already included.

22. Operating System Breakdown
Notice Windows has the majority of the market

23. Windows Windows 10 is the latest version, with touch capabilities
Most popular OS
Pros
Cons
Lots of apps
Widely used
Popularity results in hacker popularity results in security issues

24. MAC OS Apples Operating System Pros Cons
Lots of apps, but not as many as windows
Excellent for photography and design
Fewer security threats
Very reliable
More expensive

25. Linux
Open source operating system. Publically contributed to, and is free
There are different flavors and looks to Linux, so you can pick the one you like.
Pros
Cons
Free
Takes up less space than Windows and Mac
Different flavors
More secure
More work to setup…

26. Utility Programs
Helper Programs

27. Utility Programs Part of the OS
Small programs that perform special functions on the computer
Used to manage and tune your computer hardware
Some are shipped with the OS and others are stand alone

28. Types of Utility Programs
File Explorer
Disk Cleanup
Error Checking
Task Manager
Disk Defragmenter
System Restore
File History and Recovery

29. File Compression Utilities
Can take a large file and make it smaller
Makes it more feasible for you to send these files
Will find simplify repeated patterns so they take up less space.
the rain in Spain falls mainly on the plain.
becomes
? r! in Sp! falls m!ly on ? pl!.
! = ain
? = the

30. Image Compression In a vector image there is a lot of repeated color.
Hence the compression can be very effective, and you can use lossless compression.

31. Display Utilities
These utilities help you to customize your computer looks, backgrounds, colors…

32. System Maintenance Utilities
Disk cleanup is a Windows Utility that will cleanup your hard drive removing unnecessary files and giving you the space back.
Disk Cleanup removes:
temp internet files
offline web pages
temporary files

33. Hard Disk Data Saving
When you save information to the hard drive it places the info around the tracks in sectors.

34. Hard Disk Space
When data is deleted it isn’t removed, instead there is no reference to it, and it will later be written over
As the space get’s filled on the tracks it becomes hard to find places for the new data, especially if it’s large. Hence it gets divided up, and the pieces reference each other.

35. Disk Defragmenter
Defragmenting will group related data together, and make more room for new information.
Speeding up data entry and retrieval.

36. System Restore and Backup
Allows you to roll your computer back to the state it was in prior to things going astray.
Your computer takes snapshots of the different states, so that if you install a bad piece of software it can be rolled back to a prior state, and you won’t lose everything.

37. Accessibility Utilities
Some users have special needs, for instance they are blind, and can’t read the screen
Accessibility utilities provide screen readers, and other utilities to help make working on a computer more feasible for individuals with special needs.

38. Understanding how the computer stores your files
File Management
Understanding how the computer stores your files

39. File System
The OS provides an organizational structure for the files called the File System
Hierarchy for file management
Drives
Libraries
Folders
Subfolders
files

40. File Management
File Path
Navigation Pane
File
Libraries

41. File Path
Shows the location of the file

42. File Name Extensions Extension Type of Document Application .doc
Word processing document
Microsoft Word 2003
.docx
Microsoft Word 2007
.wpd
Corel WordPerfect
.xlsx
Spreadsheet
Microsoft Excel 2007
.accdb
Database
Microsoft Access 2007
.pptx
PowerPoint presentation
Microsoft PowerPoint 2007
.pdf
Portable Document Format
Adobe Acrobat or Adobe Reader
.rtf
Text (Rich Text Format)
Any program that can read text documents
.txt
Text

43. File Name Extensions Extension Type of Document Application
.htm or .html
Hyper Text Markup Language for a Web page
Any program that can read HTML
.jpg
Joint Photographic Experts Group (JPEG) image
Most programs capable of displaying images
.gif
Graphic Interchange Format (GIF) image
.bmp
Bitmap image
Windows
.zip
Compressed file
WinZip

44. File Protection
In a multi-user computer the Operating System needs to ensure that users can’t access each others files.
When the user set’s up a file they should be able to set permissions.
Read
Write/Delete
Execute
Owner
Yes No
Group
World

45. Disk Scheduling
It is a slow process to transfer data from secondary to primary memory
Disk Scheduling: The technique the OS uses to determine which requests to access secondary memory to process first

46. Disk Scheduling
Seek Time: Amount of time it takes for the heads to reach the appropriate cylinder
Latency: The additional time it takes the platter to rotate into the proper position so the data can be read or written.

47. Disk Scheduling Techniques
First Come, Firs Serve: Simple scheduling algorithm; however, not very efficient because it doesn’t take into account where the head currently is, relative to the data.
Shortest-Seek-Time: The issue with this technique, is a request may be ignored for a long time because it has a long seek time.

48. Disk Scheduling Techniques
Scan Disk: In this algorithm the head acts like an elevator. Moving towards the center, then away. Just like an elevator it processes the requests along the way.