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System Software

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System Software enables application software to interact with the computer and ... system on which a computer is based. GUI vs. command driven operating systems ... – PowerPoint PPT presentation

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Title: System Software


1
System Software
2
Components of System Software
  • System Software enables application software to
    interact with the computer and manages the
    computers resources
  • Operating System (OS) The principal component of
    system software, manages basic operations of the
    computer
  • Device Driver Helps the computer control
    peripheral devices
  • Utility Program Supports, enhances, and expands
    capabilities of existing programs
  • Language Translator Translates high-level
    language programs to machine code

3
Utility Programs
  • Backup Makes a duplicate copy of the specified
    data
  • Data-Recovery Restores data that has been
    physically damaged or corrupted
  • Virus Protection Scans files, detects, and
    removes viruses
  • Data Compression Removes redundant elements,
    gaps, and unnecessary data from files
  • Disk Scanner Cleanup Detects and removes
    unnecessary files, detects and corrects disk
    problems
  • Defragmenter Finds all scattered files on a hard
    disk and reorganizes them as contiguous files

4
Fragmentation Visualized
5
The Operating System
  • The operating system (OS) is the principal
    component of system software
  • It consists of the master system of programs that
    manage the basic operations of the computer
  • Some of the functions of the OS are
  • Memory management
  • CPU scheduling
  • Process management
  • File management
  • Security management

6
Common Operating Systems
  • Software Platform A particular operating system
    on which a computer is based
  • GUI vs. command driven operating systems
  • Disk Operating System (DOS) The original OS by
    Microsoft, command-driven user interface
  • Windows 3.X, 95, 98, etc.
  • Mac OS For Apple Macintosh computers, first
    GUI-based OS
  • Network Operating Systems Netware, Linux, Unix,
    etc.
  • What factors would you consider when selecting a
    new OS?

7
The Booting Process
  • Booting is the process of loading the OS into the
    computers main memory
  • When the computer is turned on, diagnostic tests
    are performed to check that the CPU and other
    parts of the system are running properly
  • The CPU automatically begins executing the BIOS
    stored in the ROM
  • The OS is loaded from the hard disk to the main
    memory (RAM)
  • Control is passed to the OS
  • Cold vs. Warm Boot
  • The Boot Disk A CD that contains all the files
    needed to launch the OS
  • When the computer is turned on with the boot disk
    in the disc drive, the OS files are forced to the
    BIOS, i.e. it takes precedence over obtaining the
    OS files from the hard drive
  • Once in the OS is loaded, one can perform
    maintenance, troubleshooting, etc.

8
Process
  • A process is a program in execution. Program is a
    static set of instructions. Process is a dynamic
    entity that represents the program while it is
    being executed.
  • The process states
  • New
  • Ready
  • Running
  • Waiting
  • Terminated

9
Process Management
  • Process Management is the act of carefully
    tracking the progress of a process and all of its
    intermediate states.
  • CPU Scheduling is determining which process in
    memory is executed by the CPU at any given point.
  • Mainly CPU scheduling is done in 2 ways
  • Batch processing
  • Time sharing

10
Batch Processing
  • The first Operating System was Human Operator.
  • Operator used to organize various jobs from
    multiple users into batches of jobs that needed
    the same resources . Together program and set of
    instructions in together are called Job.
  • Modern OS incorporate batch processing by
    allowing the user to define a set of OS Commands
    as a batch file .bat to control the processing of
    large program.

11
Timesharing
  • A timesharing system allows multiple users to
    interact with a computer at the same time. They
    all timeshare the same resource.
  • Timesharing create an illusion that each user has
    exclusive access to the computer. So they do not
    have to compete for resources.
  • Though is what exactly happens behind the scene.
  • The OS Manages the sharing of the resources,
    including CPU behind the scene.
  • Each user has his/her own Virtual Machine, in
    which all system resources are (in effect)
    available for use.

12
CPU Scheduling
  • CPU Scheduling is the act of determining which
    process in the ready state should be moved to the
    running state.
  • This happen when a process switches from running
    state to waiting state or terminated state.
  • Scheduling offers under 2 circumstances
  • Non-preemptive Scheduling Scheduling that occurs
    when the currently executing process gives up the
    CPU voluntarily.
  • Preemptive Scheduling Scheduling that occurs
    when the OS decides to favor another process,
    preempting the currently executing process
  • Turnaround Time The scheduling metric that
    measures the elapsed time between a process
    arrival in the ready state and its completion

13
Approach to CPU Scheduling
  • First-come first-serve (FCFS) diagram 1. Avg
    turnaround time 529.
  • Shortest job next (SJN)- diagram 2. Avg
    turnaround time 435.
  • Round robin- Every process is treated the same.
    Eventually all preempted process will be given
    another time slice on the CPU.
  • Time slice - The amount of time each process
    receives before being preempted and returned to
    the ready state to allow another process its
    turn. Avg turnaround time 668

14
Memory Management
  • The OS must employ techniques
  • Track where and how a program resides in memory
  • Convert logical program addresses
  • A logical address is a value that specifies a
    generic location relative to the program but not
    with respect to the actual main memory device
  • A physical address is an actual address in the
    main memory device
  • Address binding The mapping from a logical
    address to a physical address
  • Three memory management techniques
  • Single contiguous memory management
  • Partition memory management
  • Paged memory management

15
Single Contiguous Memory Management
  • The approach to memory management in which a
    program is loaded into one continuous area of
    memory

16
Partition Memory Management
  • Fixed Partition Technique The memory is divided
    into a specific number of partitions into which
    programs are loaded
  • Dynamic Partition Technique The memory is
    divided into partitions as needed to accommodate
    programs
  • Partition selection
  • First fit
  • Best fit
  • Worst fit
  • Which partition selection technique is better?

17
Paged Memory Technique
  • An approach in which process are divided into
    fixed-size pages and stored in memory frames when
    loaded
  • Frame A fixed-size portion of main memory that
    holds a process page
  • Page A fixed-size portion of a process that is
    stored in a memory frame
  • Page-Map Table (PMT) The table used to keep
    track of page/frame relationships

Memory
P1 PMT
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