Computers: Information Technology in Perspective By Long and Long Copyright 2002 Prentice Hall, Inc. Software Operating systems J. Holvikivi 2013

Quit Software Categories SystemSoftware ApplicationSoftware

Quit The Operating System OperatingSystem GUI Operating Systems

Quit 2.4 Algorithms – basis of software  A sequence of steps that directs the execution of a task A sheet of music A sheet of music operating instructions for a washing machine operating instructions for a washing machine instructions for constructing model airplanes instructions for constructing model airplanes  Algorithms in computers programs programs the intelligence required to solve a problem or to perform a task is encoded in the algorithm the intelligence required to solve a problem or to perform a task is encoded in the algorithm to follow the directions of an algorithm is "merely mechanical" to follow the directions of an algorithm is "merely mechanical"

Quit 2.5 The Operating System   Coordinates all software activity within a computer system: The master control program that runs the computer.   The first program loaded when the computer is turned on, its main part, the "kernel," resides in memory at all times.   The operating system sets the standards for all application programs that run in the computer. The applications "talk to" the operating system for all user interface and file management operations.   Our interaction with the OS is through the graphical user interface   Examples: DOS, Windows, Unix, Linux, Mac OS, IBM mainframe OS/390 and the AS/400's OS/400, iOS, Android

Quit 2.6Unix Bell laboratories, 1970s, universities  Many versions (AIX, HP-Unix, Linux, Solaris)  User interface: character based or GUI X- Window  Coded in C- language  Hierarchical file system root usr bin dev - lpt tmp

Quit 2.7 Directory structures: Windows and Linux  D:\Documents Eiko Eiko index.html index.html logo.gif logo.gif page2.html page2.html Images Images Photo1.jpg Photo1.jpg Photo2.jpg Photo2.jpg Friends Friends Myfriend.html Myfriend.html  Users/e/eiko Public_html Public_html index.html index.html logo.gif logo.gif page2.html page2.html Images Images Photo1.jpg Photo1.jpg Photo2.jpg Photo2.jpg Friends Friends Myfriend.html Myfriend.html

Local disk Windows OS C:\Documents Server disk Linux OS shell.metropolia.fi index.html page2.html index.html picture1.jpg logo2.gif Home directory of user x public_html Other data Workstation Local use: editing FTP, SCP Remote use through internet: visiting Web pages Creating and sending home pages

Quit 2.9 Linux commands   ls -f list all files including files starting with a dot (.login.forward etc)   ls -l (or ll) list all files, types and access rights ls *.txt list files with extension txt ls m*.* list files starting with m   passwd change password   cd change to directory

Quit 2.10 Linux commands   rm remove file   mkdir create/ make directory   rmdir remove/ delete directory   mv move or rename file   pwd (print working directory) show current dir   ps list active processes   kill terminate process   fg move to foreground process   exit

Quit 2.11 Linux access rights   chmod change access rights (+ more, - less)   Groups: user, group, others, all;   Rights: none, read, execute, write   set access rights in Linux (Putty, WinSCP), not through Windows file management

Quit Operating System Objectives  Coordinates all software activity within a computer system: The master control program that runs the computer.  The first program loaded when the computer is turned on, its main part, the "kernel," resides in memory at all times.  The operating system sets the standards for all application programs that run in the computer. The applications "talk to" the operating system for all user interface and file management operations.

Quit 2.13 Starting of an operating system  The start signal: all controllers, starting registers and program counters are set in start-state, initialized  The program counter reads the pre- determined address from memory (ROM program, bootstrap) before starting its first machine cycle  The boot program knows where operating system is located on disk: - OS is loaded into memory (RAM) - OS is loaded into memory (RAM) - jump into beginning of operating system - jump into beginning of operating system

Hard disk Windows OS Device drivers OS kernel MS Word MsWord Text file Load to memory Processor Text file Data files Device drivers and others Save Memory: RAM

Quit Operating System Objectives  Facilitate communication: user – computer user – computer computer system components computer system components computer - network computer - network  Maximize throughput  Minimize processing time  Optimize computer resources  Organize files  Provide security  Monitor system/alert user

Quit Operating System Functions  1) Control data (incl. programs) and its access. Each such item resides in the computer system as a collection of records called a file. OS takes care of manipulation of files and keeps track on storage of files. Execution of programs.  2) Provide for efficient device access. Includes routines needed to use the peripheral devices attached to the machine. To facilitate communication among computer system components, and to maximize throughput.

Quit Operating System Functions  3) Manage resources and optimize their use: memory area, peripheral devices, programs.  4) Control access to the machine (access codes, passwords), and to provide an envelope of security for the computer system.  5) Standardization of the human/ machine interface (same OS, many machines).

Quit 2.18 Operating System Features MultitaskingMultitasking ForegroundForeground KernelKernel BackgroundBackground

Quit 2.19 Operating System Interfaces MS-DOS Syntax Unix, Linux Text-Based, Command-Driven Software Macintosh Windows 9x/NT/2003/XP, 7, 8 Graphical User Interface (GUI), Icons Graphics-Based Software

Quit 2.20 Operating system architecture  Command processor monitors input devices (keyboard, mouse) and interprets commands monitors input devices (keyboard, mouse) and interprets commands  Scheduler arranges for the execution of the program arranges for the execution of the program  File manager management of bulk storage management of bulk storage users' access rights users' access rights  Resource allocator  Dispatcher coordination of time-sharing, switching of jobs coordination of time-sharing, switching of jobs

Quit 2.21 Modes of processing  Batch processing execution of jobs which are collected together with their data in a single batch without interaction with the user execution of jobs which are collected together with their data in a single batch without interaction with the user job queue: jobs waiting before being executed. FIFO (first-in-first-out) and priorities job queue: jobs waiting before being executed. FIFO (first-in-first-out) and priorities  Interactive processing dialogue with the user, immediate response dialogue with the user, immediate response  Real-time processing: response to the environment  Multitasking systems time-sharing time-sharing

Quit 2.22Time-sharing  programs waiting in memory  dispatcher executes a jump to next program's location (reload registers) & starts timer circuit - time slice for program execution 10 to 100 milliseconds - time slice for program execution 10 to 100 milliseconds  creates a virtual machine for each process  slower than real machine  priorities: longer time slices or more time slices  time-sharing within batch processing (mix of jobs, more even load on resources)

Quit 2.23Platforms  90% use Wintel (Windows & Intel) on PC  Mac OS  IBM mainframe OS/390  IBM AS/400's OS/400  Unix, Solaris, Linux, Ubuntu  Mobile platforms: iOS, Android, WP8, Meego Platform is defined by the Processor and Operating System Platform is defined by the Processor and Operating System

Quit 2.24 Platform Problems Long-term commitment Multiplatform environment Cross-platform technologies InteroperabilityInteroperability