Chapter 21.What are the two major UNIX system versions?Answer: AT & T UNIX version V, Berkeley UNIX2.What is the kernel?Answer: the UINX kernel, also called the base operating system, is the layer that manages all the hardware-dependent functions. 3.What is a shell?Answer: shell is a powerful command interpreter, which control the users interaction with UINX. 4.Briefly explain the virtual computer concept.Answer: Virtual compute is an execution environment that consists of a terminal for user interface and shared access to the other computer resources such as memory, disk drivers, CPU etc. UNIX, a multiuser operating system is implemented as a collection fo virtual computers. To the users, it appears that each of them has his or her own private pseudocomputer. 10.Name some of the UNIX variants.Answer: Linux, Solaris, UnixWare.Chapter 37. What sort of information does the man command provide?Answer: the man command provide detailed information about command usage and options.8. What is the general format of a UNIX command?Answer: the command line format:13. Name the different types if UNIX shells. What are the prompt signs for UNIX shells?Answer: Bourne Shell(the sign is $), Korn Shell(the sign is $), C Shell(the sign is %), Bourne Again Shell(the sign is $).14. What are the shell commands?Answer: shell commands are part of the shell program, these built-in commands are recognized by the shell and are executed internally.15. What are the utility programs?Answer: utility programs s are executable programs that the shell locates and executes.Chapter 44. Name the vi modesAnswer: command mode,text input mode5. Name the keys that place the vi editor in the text input modeAnswer: I,i,O,o,A,a7. Name the command that saves your files and quits the vi editor.Answer: :wq or ZZ8. Name the command that just saves your file and remains in the vi editor.Answer: :w9. Name the key that places the vi editor in the command modeAnswer:ESC10. Name the operator that deletes one line of text and the operator that deletes five lines of text.Answer: dd, 5dd11.Name the operator that deletes a character and the operator that deletes 10 characters.Answer: x, 10x12. Name the key that repeats your most recent text change.Answer: .(dot)13. Name the key that moves the cursor position to the end of the current line.Answer: $14. Name the key that moves the cursor position forward one word.Answer: w15. Name the cursor movement keys that move the cursor up, down, left, and right.Answer: k, j, h, l16. Name the key that appends the text you enter to the end of the current line.Answer: A17. Name the key that opens a line above the current line.Answer: O18. Name the key that opens a line below the current line.Answer: o19. Name the key that undoes the most recent changes.Answer: u20. Name the key that undoes all the changes on the current line.Answer: UChapter 55.Question Nbr.1234567891011121314Answerhjniklmadbefgc6. Absolute pathname: bRelative pathname: c dFilename: a e f7.a. rm filenameb. rmdir filenamec. rm -i filenamed. lp filename or lpr filenamee. cancel print-request-idf. lpstat g. lp -d printer-name or lpr -p printer-nameh. lp -3 filenamei. lsj. ls -a ls - -allk. ls ll. cd cd $HOMEm. cd directory-namen. mkdir directory-nameo. mkdir -p directory-name/directory-namep. cd /q. cat filenamer. cat filename filename9.filenameusergroupotherdrwxrwxrwx 11read- write-executeread- write-executeread- write-execute-rwxrw-rw- counterread- write-executeread- writeread- write-rw- dead.letterread- write-rw-rw-rw- enableread- writeread- writeread- write-rwxrwxrwx xyzread- write-executeread- write-executeread- write-execute-rwx- HELLOread- write-execute-rwx-x-x Memosread- write-executeexecuteexecuteChapter 61.vi -R xyz4.The vi editor uses nine buffers numbered from 1-9 to store text that is deleted or yanked during the editing job. Data stored in the buffers can be accessed by their assigned numbers. Data in the first buffer holds the latest changes and each new change of text will be stored in buffer 1 and the content of all buffers will move down. The content of buffer number 9, if any, will be lost. (Section 6.4.1)6.a: ddb: dwc: yyd: ywe: d$f: z2yyg: zph: 2p9.The .exrc file is used to tailor the vi environment. The commands and parameters that affect the vi environment, and you want to be available when using the vi editor, are typed in this file. The content of this file will be executed when vi is invoked.10.:!date 11.:r date 13.The vi editor recovery option is -r that is