16. Computer Systems   Basic Software 2
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  • Instruction Retry A function that automatically retries the execution of an instruction when a malfunction occurs Failure Management Program Records the failure circumstances, (if malfunction repeats) isolates location where failure occurred and reconstructs the system
  • Refer to Text Page 109 & 110 for MVS Configuration and it’s Characteristics
  • Refer to Text Page 110 & 111 for UNIX Configuration and it’s Characteristics
  • Refer to Text Page 111 & 112 for Windows Configuration and it’s Characteristics
  • Linux - a Unix-like operating system named for its author, Linus Torvalds. Linux was designed to provide personal computer users a free or very low-cost operating system comparable to traditional and usually more expensive UNIX systems. Although copyrights are held by various creators of Linux's components, Linux is distributed using the Free Software Foundation's copyleft stipulations that mean any copy is in turn freely available to others. Unlike Windows and other proprietary systems, Linux is publicly open and extendible by contributors. It is considered fast and reliable as both a Web server and a workstation and runs on many different kinds of hardware, including the Alpha, Amiga, Atari, IBM, Intel, PowerPC/Macintosh, SGI, and Sun Sparc platforms. Some vendors do sell collections, or distributions, of the Linux kernel, plus Linux drivers, applications, and utilities for a price. Linux is sometimes suggested as a possible publicly-developed alternative to the desktop predominance of Microsoft Windows. Although Linux is popular among users already familiar with UNIX, it remains far behind Windows in numbers of users.
  • NetWare, made by Novell, is the most widely-installed network server operating system . Initially very successful in installing its products in large and small office local area networks (LANs), Novell has redesigned (or at least refeatured) NetWare to work successfully as part of larger and heterogeneous networks, including the Internet. NetWare's primary competitor is the Microsoft Windows NT operating system.

16. Computer Systems   Basic Software 2 16. Computer Systems Basic Software 2 Presentation Transcript

  • Part2: Computer Systems Chapter 2: Basic Software
  • File Management
    • Helps the user to keep track of data and programs
    • Most data is stored in auxiliary storage devices, file handling plays an important role in data management
    • 1. File system
        • An OS component that allows the user or
        • programmer to create, delete, modify, and
        • manipulate files and programs by name
        • File concept and configuration in low-end computers
          • Files simple record character strings
          • There is no difference between data and programs
          • Cluster – basic unit of disk space allocation, with one or more contiguous sectors
          • Directory – list of files stored on a disk or other device. Often used to convert a file name to a physical address
    File Management
  • File Management
    • File system
      • Cluster
        • set of several sectors
        • I/O unit between auxiliary devices and RAM
        • When data cannot be filled in one cluster, an unused cluster is coupled and the remaining data written in this cluster. Not necessary for the coupled cluster to be contiguous.
  • File Management
    • File system
      • Directory
        • Register where the file management information is recorded and stored
        • Hierarchical structure
        • Root, directories (folders), sub-directories (sub-folders)
  • File Concept
  • File Management
        • File operation
          • Directory is automatically setup by the OS when PCs or workstations start up
          • It is a root directory, user have access to it
          • User has to move to target directory in order to access a directory or file
          • Directory
          • - Home directory : can be used by the user; user can create and access the sub-directories and files
          • - Current directory: directory in current use
  • File Management
          • Path: the route along which to search for that file is specified.
          • - Absolute path: path to target directory or file from the
          • root directory
          • - Relative path: path to target directory or file from the
          • current directory
          • Command
          • - A request to the OS for a service (DOS command)
          • Extension and wild cards:
          • E.g. dir *.doc – show all files with extension DOC
  • File Management
          • File operations in GUI environments
  • File Management
    • Hierarchical Structure
    . DIR 1 DIR 2 DIR N FILE 1 FILE 2 FILE N DIR 2.1 DIR 2.N FILE 2.1 FILE 2.N
  • Roles in File Management
    • Roles
      • Maintain File Allocation Table (FAT)
        • Chain of clusters for each directory or file
        • Properties for each directory or file
      • Read/Write Operations
        • Exclusive write
        • Multiple reads
      • Backup Operation
  • Roles in File Management
    • Roles
      • Utilities
        • List, copy, move, delete, and rename
        • Backup and recovery
        • Disk diagnose
        • Defragmentation
  • Security Management
    • Protection of a computer and its resources from unauthorised access by persons, acts, or influences and that includes many sub-functions, such as creating, deleting, and controlling security services and mechanisms
  • Aims of Security Management
    • Confidentiality
      • Against illegal access (e.g. data encryption)
    • Integrity
      • Against unauthorized modification (e.g. security access list)
    • Availability
      • Prevents the obstruction of the use by a legitimate user
  • Security Management
    • OS performs security control through:
      • Access control
        • Permissions assigned to legitimate users, who have access to computer resources
      • Flow control
        • Prevents leakage of information to users that are not authorized as legitimate users
      • Authentication
        • Validating the user (login)
  • Failure Management
    • Utility to manage failed processes
    • Utility to manage failed resources
  • Failure Management
    • Concerned with impact of system failure:
      • Instruction Retry
        • Automatically retries execution of specific instructions when failure occurs
      • Failure Management Program
        • Failure circumstances are recorded if computer operates normally after retry
        • If failure occurs again after retries, location where failure occurred is isolated
        • Reconstruct the system
  • Failure Management Normal operation Retry Malfunction System reconstruction Malfunction Normal operation Failure management program Failure management program The failure circumstances are recorded The location where the failure occurred is separated Instruction retry and failure management program
  • Supervisor
    • A monitoring program functioning as the central part of OS
    • Contains a command processor or shell, an I/O control system (IOCS), a file system, and interrupt handler routines
    • Performs resource distribution and program control to implement TSS (Time sharing system), multi-programming, etc.
  • Where to Get More Information
    • Deitel, H.M., 1990, Operating Systems . (Second Edition). Addison Wesley.
    • Silberschatz, A. and Galvin, P.B., 1994, Operating System Concepts . Addison Wesley.
    • Tanenbaum, A., 1995, Distributed Operating Systems . Prentice Hall.
    • Davis Rajkumar, 2001, Operating Systems A systematic View (Fifth Edition), Addison Wesley
  • Operating System System disk Printer System constants and parameters Interrupt handler routines Command processor I/O Control system File system Transient area The components of a typical microcomputer operating system Resident operating system
  • OS Categories
    • Real-time OS
    • Single-user, single-task OS
    • Single-user, multi-task OS
    • Network OS
    • Multi-user OS
  • Real-time OS
    • To control machinery, scientific instruments and industrial systems
    • Usually a "sealed box"
      • Very little user-interface capability
    • Manage resources such that each operation executes in precise amount of time
  • Single-user, Single-task OS
    • No user differentiation
    • Only one task can execute at anytime
    • Example Palm OS
  • Single-user, Multi-task OS
    • No user differentiation
    • Multiple tasks can execute at anytime
    • Example: Windows 95
  • Network OS
    • User differentiation
      • Separate software and hardware profiles
      • Only one user can operate at anytime
    • Resources are shared simultaneously
    • Example: Windows 2000/XP
  • Multi-user OS
    • User differentiation
      • Separate working segment
      • Separate software and hardware profiles
    • Resources are shared simultaneously
    • Example Unix
  • Types of OS
    • Multiple Virtual Storage (MVS)
    • UNIX
    • Windows
    • MacOS
    • Linux
  • Multiple Virtual Storage (MVS)
    • An old IBM mainframe operating system that continues to be used for some systems.
    • The most commonly-used operating system used on IBM mainframes; other operating systems are VM and DOS/VSE.
    • http://search390.techtarget.com/sDefinition/0,,sid10_gci212618,00.html
  • MVS Configuration
  • Multiple Virtual Storage (MVS)
    • Characteristics:
      • OS for high-end general-purpose computers
      • Provides multi-user function, which enables simultaneous MVS use by multiple users
      • Provides multi-task function, which enables simultaneous processing of multiple tasks
      • Adopts approach of multiple address space
      • One logical address space reaches up to 2GB
      • Contains all file organization functions
  • UNIX
    • An interactive time-sharing operating system invented in 1969 by Ken Thompson after Bell Labs left the Multics project, originally so he could play games on his scavenged PDP-7.
    • Dennis Ritchie, the inventor of C, is considered a co-author of the system.
    • http://whatis.techtarget.com/definition/0,289893,sid9_gci213253,00.html
  • UNIX Configuration
  • UNIX
    • An OS that can be used by multiple users, which each user can simultaneously perform multiple job processing
    • Contains control program called Kernel:
      • Controls the system resources
      • Performs process management
    • Shells and commands:
      • Interprets commands input by the users and calls the kernel function
      • Execute a program called shell script (which combines commands)
  • UNIX
    • Characteristics
      • Distributed processing is presupposed
      • Developed assuming that would be used in workstations
      • Provide multi-user functions
        • Procedure called log-in: receive service; log-out: report completion
      • Multiprocessing function (multi-programming)
      • Communication protocol TCP/IP used to connect computers of different manufacturers
      • Use of commands in an interactive mode
      • Instruction rights in interactive mode – human interface e.g. X-Window
      • Program development tools are abundant
  • Unix Family Tree UNICS (Uniplexed Operating and Computing System) 7 th Edition [1978] BSD (Berkeley Software Distribution) [1969] 5 th Edition [1973] 6 th Edition [1976] SVR5 (System V) [1979] [1983] Sun OS 5.x/Solaris HP HP-UX IBM AIX SGI IRIX DEC Digital UNIX (formerly OSF/1) Sun OS 4.x DEC Ultrix Canon NextStep Apple OS X
  • Why UNIX?
    • Universally used for high-end number crunching applications (e.g. CAD/CAM and scientific visualisation)
    • Preferred OS platform for running internet services such as WWW, DNS, DHCP, NetNews, Mail, etc. due to networking being in the kernel for a long time now
    • Easy access to the core of the OS (the kernel) via C, C++, Perl, etc.
    • Stable operating environment
    • The availability of a network extensible window system
    • The open system philosophy
  • Unix Cold Boot Power-On Self Test (POST) Probing the bus for boot device ROM Reading the boot program Read in the boot kernel Initialize the system Start dummy system processes Start init Execute startup scripts
  • Unix Shut Down
    • All logged on users are warned about the impending shutdown and given a chance to close files and to log out.
    • Further login may be blocked.
    • init is asked to change the run level from the multiuser state to either a single user or a safe-to-power-off state.
    • All running processes are notified that the system is going down (this allows a number of programs to save vital information to disk).
    • The system goes through the appropriate shutdown scripts to shut down running services and daemons.
    • The file systems on disks are synchronized; that is, unwritten buffers are committed to disk.
    • Machine may be powered off.
  • Unix Security Management
    • System Level
      • Login/logout
      • Supervisor versus user
      • Auditing
    • File Level
      • Permission modes (read, write, execute) for owner and group association for a file
  • Unix Job Management
    • Job control is basically an explicit interaction with processes via shell command
    • Three types of shell
      • Bourne shell – input and output control
      • C shell – good for C programming
      • Korn shell – combining Bourne and C shell
  • Unix Job Management
    • Kernel
      • Core of the operating system
      • Manages hardware resources like CPU, memory, input/output devices, etc.
    Unix commands Interpret requests Execute requests User Shell Kernel
  • Unix Structure Shell File System Kernel Device Drivers Process Memory
  • Unix Commands UNIX DOS REMARKS tar1 backup tape archive cd cd change directory fsck chkdsk file system check clear cls clear screen cmp compare compare files cp copy copy a file date date set/show date and time rm del remove a file ls dir list directory grep find global regular expression print format format format disk mkdir md make directory more more show file page at a time lp print line printer rmdir rd remove directory set set show/set environment variables sort sort sort a file cat type concatenate a file
  • Unix File Management
    • Hierarchical File System
    • Each user has his own workspace
    / var lib dev bin usr
  • Unix Process Management
    • For each new process, the kernel sets up an address space (in memory) consisting of the following logical segments:
    text data bss user stack kernel stack program's instructions initialized program's variables uninitialized program's variables variables allocated locally and parameters passed to functions in the program
  • Unix Process Management
    • Mode switching
      • Kernel-mode – those processes carrying out kernel instructions
      • User-mode – those processes, created directly by the users, whose instructions are currently executing in the CPU
      • At any given time, a process can be in user-mode, kernel-mode, sleeping, waiting on I/O, and so on
  • Unix Process Management
    • The process scheduling subsystem within the kernel uses a time slice of typically 20ms to rotate among currently running processes.
    • Each process is given its share of the CPU for 20ms, then left to sleep until its turn again at the CPU.
    • This process of moving processes in and out of the CPU is called context switching.
    • The kernel makes the operating system appear to be multi-tasking (i.e. running processes concurrently) via the use of efficient context-switching.
  • Unix Process Management
    • Process States
      • Resident – currently on the run queue
      • Sleeping – waiting on a pipe, completion of I/O, terminal input, memory
      • Zombie – a process with no swappable image but a structure in memory
      • Stop
  • Unix Memory Management
    • Virtual memory (VM)
      • VM = Physical RAM + Swap space (disk space)
    • Pages
      • The Memory is divided into manageable chunks called pages (usually 4KB or 8KB per page)
  • Unix Memory Management
    • Caching
      • When the kernel loads a page from RAM for use by the CPU, it also prefetches a number of adjacent pages and stores them in the cache.
      • Since programs typically use sequential memory access, the next page needed by the CPU can now be supplied very rapidly from the cache.
  • Unix Memory Management
    • Cache Memory
      • The RAM cache is simply a small amount of very fast (and thus expensive) memory which is placed between the CPU and the (slower) RAM
        • L1 cache – on-chip cache is small but fast (being on-chip)
        • L2 cache – not on-chip (thus a bit slower) and can be quite large, sometimes as big as 16MB for high-end CPUs
  • Unix Memory Management
    • Demand Paging
      • When a process starts in Unix, only few and not all its memory pages are read into RAM from the disk at once.
      • After the CPU digested the pages in RAM, a page fault occurs; signaling the kernel to load the next few pages from disk into RAM. This is called demand paging.
  • Unix Memory Management
    • Swapping
      • This occurs when there is not enough physical RAM to accommodate all the processes.
      • It makes use of the available virtual memory by a process known as swapping.
      • It selects the least busy process and moves it to disk.
      • As more RAM becomes available, it swaps the process back in from disk into RAM.
  • Windows
    • More than half of PCs around the world is Windows
      • Windows
      • Windows 95/98//ME
      • Windows NT/2000/XP (http://www.microsoft.com/windowsxp/default.asp)
    • http://www.microsoft.com/ms.htm
    • http://www.mactech.com/macintosh-c/chap04-1.html
  • Win2K
  • Win9x configuration
  • Windows
    • GUI characteristics
      • Desktop approach
      • Multitask function
      • Mouse pull down menu / dialog box manipulation
    • WinXP
      • Strengths of security, manageability and reliability of WinNT
      • GUI features of Win9x and WinME
      • Plug-and-play
      • Different versions to suit different users (cost)
  • Windows .Net Boot-up Power On Bootstrap Loader Load OS & Device drivers Launch startup Power-On Self Test Reset Initialize hardware
  • Windows .Net Security Management
    • System Level
      • Login/logout
      • Enterprise administrator, local administrator, backup operator, user
      • User account and computer account
      • Security policy and group policy
      • Auditing
      • Hibernation
  • Windows .Net Security Management
    • System Level
      • RAID 0, RAID 1, and RAID 5
    • File Level
      • Permission modes
      • Data encryption
    • Printer Level
      • Permission modes
  • Windows .Net Job Management
    • Two interfaces
      • Command interface
      • Graphical interface
    • Startup versus scheduled
  • Windows .Net File Management
    • Hierarchical file system
    • Windows explorer interface
    • Virtual file system
    • Compression
  • Windows .Net Disk Management
    • Enhanced check disk utility
    • Volume shadow copies and shadow copy restore
    • Virtual disk services
    • Area network (SAN) participation
  • Windows .Net Process Management
    • 64-bit operating system
    • Pre-emptive and prioritized multi-tasking
    • Symmetric multi-processing (SMP)
  • Windows .Net Memory Management
    • Up to 256GB RAM
    • Dynamic virtual memory
    • Memory mirroring
    • Hot-add memory support
    • Non-uniform memory access
  • Windows .Net Failure Management
    • Update service patches and hot fixes without restart
    • Automated system recovery
  • MacOS
    • Developed by Apple Computer for Macintosh
    • http://www.apple.com/
  • MacOS
    • Almost all operations can be performed with the mouse
    • Consistent GUI
    • GUI elements are abundant, hence claims to be “easy” for beginners
    • Different versions for different types of users
      • Mac OS X
      • Mac OS X Server
      • Rhapsody
    • Latest Mac OS X 10.1.1 provides improved USB, FireWire, and Networking support
  • OS X Interface
  • OS X
    • Features
      • Multi-user
      • Virtual file system
      • Symmetric multi-processing (SMP)
      • Basic threading packages
      • Pre-emptive multi-tasking
      • Virtual memory with memory protection and dynamic memory allocation
  • Linux
    • UNIX-based OS launched in 1991 by Linus Torvalds
    • The software is free: source code released to public
    • Copyright is protected by GPL (GNU Public License)
  • Network OS
    • OS used to construct LANs
    • SNMP functions
    • Netware
      • Developed by Novell
      • File sharing / printer sharing functions
    • LAN Manager
      • Distributed file system developed and supported by Microsoft
  • Middleware
    • A class of software that helps with the translation of messages and communications between client and servers
    • Any set of routines or functions that allow two dissimilar programs to interoperate
      • Database Management System (DBMS)
      • Communication Management System
      • Software Development Support Tool
      • Operation Management Tool
      • Object Request Broker (ORB)
  • Database Management System
    • Aimed at efficient database creation/maintenance/operation
    • 3 main characteristics
      • Integrity: prevents generation of data inconsistently
      • Security: protect data secrecy by setting database access rights
      • Failure recovery: failure and recovery plan to recover database promptly in the event that database fails
  • Communication Management System
    • Aimed at supporting computer network construction/operation
    • 3 main characteristics
      • Network Independence
      • Network Flexibility: provides flexibility to devices and network mechanism; construction of network systems with high expandability is enabled
      • Network Transparency
  • Software Development Support Tool
    • Supports computer-aided software development
    • Aimed at achieving development labour savings and software quality improvements
    • CASE tools
      • Upstream CASE tools: support high-end process (e.g. analysis, design, etc) of software development
      • Downstream CASE tools: support lower-end process (e.g. programming, testing, etc)of software development
      • Maintenance CASE tools: support operation and maintenance of developed software
      • Integrated CASE tools: support overall functions from upstream to maintenance CASE tools
  • Operation Management Tool
    • Aimed at supporting the operation duties of system operation
    • Characteristics
      • Multiplicity optimization of multi-programming
      • Allocation of system resources to reduce response time at peak periods
      • Grasp of operating conditions of system resources
      • Recording of a ccounting information and creation of summaries
      • Logging of operation records
  • Object Request Broker
    • It is the programming technique that acts as a "broker" between a client request for a service from a distributed object or component and the completion of that request
    • Having ORB support in a network means a client program can request a service without having to understand where the server is in a distributed network or exactly what the interface to the server program looks like
    • Components can find out about each other and exchange interface information as they are running
    • An ORB uses the CORBA Interface Repository to find out how to locate and communicate with a requested component
    • http://searchmiddleware.techtarget.com/sDefinition/0,,sid26_gci214209,00.html