1. User Interfaces Operating Systems Lecture 2, 20 March 2003 Mr. Greg Vogl Uganda Martyrs University

2. 20 March 2003 Operating Systems: User Interfaces2 Overview  System calls Required to interact with hardware  Command language Enter commands through terminal or shell Can be used to create batch files or shell scripts  Job Control Language (JCL) Submitting batches to mainframe  Graphical User Interface (GUI) windows, menus, icons, pointing device

3. 20 March 2003 Operating Systems: User Interfaces3 System Calls  Similar to ordinary library function calls  Target of function call is system code part of OS rather than part of calling program  Higher level calls are APIs call lower level system functions used to develop programs for the target OS Windows NT has high security; only offers APIs

4. 20 March 2003 Operating Systems: User Interfaces4 UNIX system calls: file I/O  Creat: creates a file  Open: opens a file for read/write etc.  Read: reads bytes from file into buffer  Write: writes bytes to file into buffer  Close: frees file from use by the process  Lseek: moves to file position  Link: creates another name for the file

5. 20 March 2003 Operating Systems: User Interfaces5 UNIX system calls: processes  Fork: creates copy of current process  Exec: replaces current process with new one  Exit: terminates process, returns to parent  Kill: sends software signal to terminate process  Pause: suspends execution of a process  Signal: control signals using specified function

6. 20 March 2003 Operating Systems: User Interfaces6 DOS Software Interrupts  Interrupt vector table in first 1K of memory  Interrupts processor like hardware interrupts  Each vector has some system functions  Interrupt 21H has many functions for: Character I/O, file/directory, process and memory management, date/time, etc.

7. 20 March 2003 Operating Systems: User Interfaces7 Command Languages  Used for on-line but also batch processing  Used to start programs  Also used to modify user environment prompt, path, working directory, etc.

8. 20 March 2003 Operating Systems: User Interfaces8 UNIX commands  command- name options arguments #comment 0 or more options beginning with dashes (-) 0 or more arguments are often file names Comment is ignored, used for documenting scripts

9. 20 March 2003 Operating Systems: User Interfaces9 UNIX shell scripting  shell script commands saved in a file and run as a program  programming-language features variables, functions, if, case, for/while loops, etc.  different shell languages have differing features sh, csh, ksh, bash, etc.

10. 20 March 2003 Operating Systems: User Interfaces10 UNIX file/folder commands  pwdshow current directory  lslists files in current directory  cdchange to a different directory  catdisplay file contents  cpcopy file  mvmove or rename file  rmdelete file

11. 20 March 2003 Operating Systems: User Interfaces11 Other UNIX commands  wccount characters, words, lines  sortsort lines of a file  grepsearch for a pattern in file lines  findsearch for files with a given name/pattern  dateshow date and time  echorepeat a line of text  whodisplay users logged on the system  mandisplay documentation about a command  exitclose the shell (logout if the only shell)

12. 20 March 2003 Operating Systems: User Interfaces12 Perl  Text processing language  Combines features of C, UNIX shells, etc.  Often used to make programmed Web pages  Can be used for system administration tasks

13. 20 March 2003 Operating Systems: User Interfaces13 MS-DOS  Similar to UNIX but simpler (e.g. only one user)  UNIX-like directory structure  Batch files (.bat extension)  command-name options arguments Options begin with forward slashes (/)  Command.com Interprets “internal” DOS commands like UNIX shell  External DOS commands are separate programs stored in folder c:\windows\command in Windows 98

14. 20 March 2003 Operating Systems: User Interfaces14 Internal DOS commands  CDchange or display the working folder  DIRdisplay contents of folder  TYPEdisplay contents of file  DELdelete file  COPYcopy file  TIMEdisplay and change time  DATEdisplay and change date  CLSclear the screen  SETset or display environment variables

15. 20 March 2003 Operating Systems: User Interfaces15 External DOS commands  FDISKpartition a disk  FORMATadd a file system to a disk  CHKDSKexamine and repair a disk  XCOPYpowerful version of COPY  MEMdisplay DOS memory usage  MOREdisplay file one screen at a time  HELPdisplay command documentation

16. 20 March 2003 Operating Systems: User Interfaces16 DOS Options  dirdisplays contents of current folder filename, ext, size, date, time, windows filename  dir/ppauses after each screen  dir/wuses wide list format (brief)  dir/sdisplays all subdirectories

17. 20 March 2003 Operating Systems: User Interfaces17 More DOS Options  dir/oddisplays files in order of date  dir/o-dsame but most recent date first  dir/adisplays file attributes directories, hidden, system, read-only, archive  dir/ahdisplays hidden files only  dir/?displays help with the dir command

18. 20 March 2003 Operating Systems: User Interfaces18 DOS Path  Fully specifies the location of a file disk, folder(s), filename, extension e.g. c:\windows\command\fdisk.exe shared computer, shared folder, filename, ext. e.g. \\xpacer\SharedDocs\OS\index.htm  OS uses search path to look for commands type PATH at DOS prompt put SET PATH command in autoexec.bat file

19. 20 March 2003 Operating Systems: User Interfaces19 DOS Batch Files  text file,.bat extension, contains commands  useful for multiple file move/copy/delete  can also run other programs and batch files  useful for repeating tasks on many computers  can keep networked client PCs identical

20. 20 March 2003 Operating Systems: User Interfaces20 Using DOS Batch Files  To create, edit or view a batch file use text editor (DOS Edit, Notepad or WordPad)  To run a batch file double-click in Explorer, or type its name at the DOS prompt or Run dialog  To get information on any DOS command type the command followed by /?

21. 20 March 2003 Operating Systems: User Interfaces21 Useful DOS batch file commands  xcopypowerful version of copy  deltreedelete directory and all subdirectories  callcalls another batch program  gotogo to labelled line in a batch file  forruns command on each file in a set  ifconditional  netWindows networking functions  echodisplays messages or command echoing  remremark (documentation line)

22. 20 March 2003 Operating Systems: User Interfaces22 Job Control Languages  Used on large computers for batch jobs: No human interaction/delays/interruptions Routine jobs e.g. payroll, financial reports Used resources are predictable, scheduled Must manage errors without intervention  Jobs are given rank/priority  Jobs are allocated memory, processor time

23. 20 March 2003 Operating Systems: User Interfaces23 Graphical User Interfaces  Usually an addition to command interfaces e.g. Windows (DOS), X Windows (UNIX)  Features include: overlapping windows screen cursor moved by pointing device desktop, icons, taskbar, menus, dialog boxes buttons, scroll bars, lists