User Interface, File System

1
User Interface, File System IOCS

• Davis Rajkumar (6th), Chp. 5

2
Overview

• User interface functions
• Kinds of user interfaces
• File system functions
• Logical vs physical I/O
• Directory management
• Disk management
• IOCS functions
• IOCS vs file system
• Resident vs Transient
• Boot process

3
OS Basic Functions

• User interface
• File management
• Device management (IOCS)
• Processor (or process) management
• Memory management
• Communications systems

Chapter 6 Part V
4
Shell, File System, IOCS
Applications
Hardware
5
User Interface Functions

• Users
• Human users generally use application programs
• Application programs use API
• Enable users to communicate with operating system
• User interface functions
• Receive commandsaccept instruction from user
• Transform commandsconvert command from user
  friendly input to machine instructions behind
  every command is a program
• Perform commandsexecute the machine instructions

6
Kinds of User Interfaces

• Command line interface
• Remember and type commands
• Text based
• Graphical user interface
• Point and click, or perform other actions
  representing commands
• Picture (graphics) based
• Voice-activated interface
• Remember and speak, or respond to options
• Voice based
• Menu driven interface
• Select choices from a menu
• Voice, text, or graphics based

7
Command Languages

• Each user interface responds to commands
• Commands for each OS called command language
• Microsoft's DOS
• Unix shellsBourne, Bash, C-shell, tsch,
• IBM's REX, JCL, and others

8
User Commands

• DOS commands App.B, pp.581-591
• Unix commands App.C, pp.593-602
• IBM/OS JCL commands App.D, pp.603-619
• Command examples
• Launch program run fileName
• Terminate program C
• Create or modify file edit fileName
• Display file type fileName
• List directory dir
• Format disk initialize device label
• Check disk show devices/full device

VAX/VMS commands ref http//h71000.www7.hp.com
/doc/72final/6017/6017pro_contents.html
9
Command Execution

• User issues command, such as double-click on
  NotePad icon
• Shell (GUI) receives double-click
• Shell interprets double-click on icon as "run
  NotePad"
• Shell requests schedule to create and schedule
  process for NotePad
• Schedule sets up Process Control Block and puts
  NotePad process in schedule queue
• Once NotePad's turn arrives, its image is loaded
  and run

10
Batch Commands or Scripts

• Batch files or scripts contain control flow
  commands and other user interface commands
• Usually text files
• Interpreted by shell
• Enables doing complex tasks using simple commands
  of user interface

11
File System Functions

• Provide structure and programs to
• Keeps track of data and programs files stored on
  secondary storage devices
• Access files stored on secondary storage devices
• Interacts with operating system
• Structure sequence of bytes, sequence of
  records, linking of noncontiguous records,
  directory
• Some programs functions
• Files creation, display, access (open, read,
  write, close), deletion, encryption/decryption,
  tracking location and attributes, authentication
  for access
• Directory create entries, modify entries,
  display content, delete entries

12
File Systems

• FAT (File Allocation Table)
• Simple system with sever limitations on
  partition size, number of files, and filename
  DOS
• HPFS (High Performance File System)
• Improvement on FAT by allowing larger
  partitions, better use of disk space and more
  information about files OS/2
• NTFS (New Technology File System)
• Successor to both FAT and HPFS. Combines
  simplicity of FAT with advances of HPFS. NT
  Family
• NFS (Network File System)
• Developed for sharing files over a network
  SunOS

13
Logical vs Physical I/O

• File manipulation occurs in programs (logical)
  and on storage media (physical)
• Logical I/Ofile system functions
• Openassociates File Control Block (FCB) with
  file
• Read/writeget (or put) relative record
• Closefinalize writes and release FCB
• Physical I/OIOCS functions
• Openestablishes link from memory locations for
  buffers and pointer to media containing data
• Read/writeseek track and sector, read (or write)
  block of data
• Closeflush write buffer, mark file as
  accessed/modified, release buffers and pointer

14
Logical and Physical Record

• Logical record
• Record as used in program
• Fields in particular order of certain data type
• Physical record
• Record as stored on media
• Block of bits transferred from media to memory
  (read) or memory to media (write)
• Block
• Amount of data read/written at one time
• May be smaller (some fieldsspanned record) than
  logical record, or larger (multiple logical
  records) than logical record

15
Disk Space Management

• File system responsible for allocation of disk
  space to records of files
• Tracks location of records by maintaining
  directory with address of first record in each
  file and pointers (links) between records
• Contiguous records most efficient
• Fragmentation records of file not contiguous
• Defragmentation rewriting records of file to
  make records contiguous

16
Directory Management

• File system creates directory entries
• When file created, file systems write new entry
  to directory with file's name, address,
  attributes
• File system uses directory to lookup file's
  attributes and address when file opened
• When file deleted, file system marks directory
  entry to show file no longer exists

17
IOCS Functions

• Generates primitive physical I/O commands
• Communicates directly with peripherals
• Frequently used by file system for physical I/O

18
Resident and Transient

• Transient routines
• Loaded in memory
• Executed
• Terminate
• Removed from memory
• Resident routines
• Loaded in memory and stay there
• Ready for execution when needed

19
Boot Process

• Power supply turns on and gains strength
• Goes to BIOS to run its boot routine
• Power on self test (POST)
• BIOS runs initialization routines in devices
  chips, memory test, and system inventory
• Identifies boot device and loads master boot
  record (MBR)usually jump instruction to boot
  routine
• Boot routine loads operating system kernel
• Kernel starts executing
• Initializes from configuration files
• Executes initialization scripts or batch files
• Process starts from BIOS memory address and pulls
  up system by "bootstraps," hence "boot"

20
Shell, File System, IOCS
Applications
Hardware
21
Summary

• User interface enables user to communicate with
  OS
• Kinds of user interfacestext, voice, graphical,
  menu
• File system provides structure and programs to
  access and track files
• Logical I/O uses fields and relative record
  position physical I/O uses blocks of bits along
  sectors in tracks
• Directory management creates and maintains
  directory entries for files and subdirectories
• Disk management allocates and supervises use of
  disk space by files

• IOCS generates primitive I/O instruction to
  communicate directly with devices
• Transient routines loaded in memory, executed,
  and removed
• Resident routines loaded in memory and remain
  ready for execution
• Boot process
• Power on
• POST
• BIOS system startup
• Load MBR
• Kernel load
• Kernel initialization
• Run initialization scripts