5 The Shell, the IOCS, and the File System

© 2005 Pearson Addison-Wesley. All rights reserved Figure 5.1 The components of a modern operating system.

© 2005 Pearson Addison-Wesley. All rights reserved Operating System Functions User interface –Mechanism for communicating with OS File system –Manipulate files by name Device management –Communicate with peripherals

© 2005 Pearson Addison-Wesley. All rights reserved Operating System Functions Processor management –Manage the processor’s time Memory management –Manage memory space Communication support –Inter-computer communication See Chapter 6

© 2005 Pearson Addison-Wesley. All rights reserved The Application Program’s Interfaces User interface part of application program –Active when program running Application programming interface –Link to operating system –Library of system calls –Referenced in source code

© 2005 Pearson Addison-Wesley. All rights reserved The Operating System’s User Interface Allows user to issue commands to OS Types of user interfaces –Command line interface or shell –Menu interface –Graphical user interface –Voice-activated interface –Web-form interface

© 2005 Pearson Addison-Wesley. All rights reserved Figure 5.2 The user interface accepts, interprets, and carries out commands.

© 2005 Pearson Addison-Wesley. All rights reserved Figure 5.3 A graphical user interface.

© 2005 Pearson Addison-Wesley. All rights reserved Figure 5.4 The user interface layer can support several different interfaces.

© 2005 Pearson Addison-Wesley. All rights reserved The Command Language Command language –The set of available commands and syntax rules –Each command activates a specific service Batch file –A set of pre-defined commands stored in a file

© 2005 Pearson Addison-Wesley. All rights reserved Figure 5.5 The user interface links to a number of routines, each of which performs a single service.

© 2005 Pearson Addison-Wesley. All rights reserved Figure 5.6 Launching an application program. a. The user selects the program.

© 2005 Pearson Addison-Wesley. All rights reserved b. The user interface calls the launch program routine.

© 2005 Pearson Addison-Wesley. All rights reserved c. The application program is loaded into memory and started.

© 2005 Pearson Addison-Wesley. All rights reserved Figure 5.7 The file system layer. The file system keeps track of the data and programs stored on disk.

© 2005 Pearson Addison-Wesley. All rights reserved Figure 5.8 The location of every file stored on a disk can be found by searching the disk’s directory.

© 2005 Pearson Addison-Wesley. All rights reserved Launching a Program User issues a launch command –Command names target program File system reads directory File system searches directory File system extracts program address Device management layer loads program Operating system starts program

© 2005 Pearson Addison-Wesley. All rights reserved Open and Close Open –New file – create directory entry –Existing file – retrieve directory –Make file available Close –Update directory –Make file unavailable