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Correct answer is (d) ctrl-u

The explanation is: If the command line CONTAINS too many mistakes, we could prefer to kill the line altogether without EXECUTING it using ctrl-u. It ERASES EVERYTHING in the line and returns the cursor to the beginning of the line.

Correct choice is (d) ctrl-q

Easiest explanation: ctrl-q RESUMES the scrolling of screen output and UNLOCKS the KEYBOARD. Ctrl-h is used to erase character by character when BACKSPACE doesn’t work while and Ctrl-c interrupts the program and bring back the prompt.

Correct choice is (c) locks keyboard

To explain: There are various keyboard COMMANDS to try when THINGS go wrong. One of these commands is Ctrl-s which STOPS scrolling of SCREEN OUTPUT and locks the keyboard.

The correct choice is (b) ctrl-H

Easiest explanation: Sometimes it may happen that BACKSPACE doesn’t work and whenever it is pressed, ^H is displayed on the terminal. To RESOLVE this problem, we can USE control key i.e. ctrl-H. Ctrl-u is used for killing a line altogether without executing it and Ctrl-c interrupts the program and bring back the prompt.

Right answer is (d) ctrl-c

The explanation is: Sometimes, a program goes on running on for an HOUR and does not seem to complete. To interrupt that command we can use the CONTROL KEY, ctrl-c. Ctrl-h is used to ERASE CHARACTER by character when backspace doesn’t work.

The correct answer is (b) tee

Easy explanation: tee is an EXTERNAL command which handles a STREAM of CHARACTERS by duplicating its input. It saves one COPY in a file and writes the other to standard output. tee command can be placed anywhere in a pipeline.

The correct option is (a) True

The EXPLANATION: Since MAN is also a UNIX command, it is NECESSARY to know how man itself is used. For this purpose, use the same command to VIEW its own documentation:

Right answer is (c) passwd

For explanation I would say: Since UNIX is a multiuser system, it requires a PASSWORD from every user who wants to log in to the system to help ensure that all the data and files of the user are secure from HACKERS and ERRANT users. A user can simply change his/her login password by using the passwd COMMAND. Simply type this command on the terminal and then enter the old password, which after successful verification would allow the user to input a new password for his login.

Right option is (a) display output with HEADER INFORMATION

Easy explanation: While most UNIX commands have a feature to AVOID cluttering the display with display information, who command does have a header option( -H ). This option prints the COLUMN headers ALSO.

Correct answer is (a) True

For explanation: History command displays the list of RECENTLY USED commands by the user which means WHATEVER commands are used by the user in the current session will be displayed on the terminal using history command.

The correct OPTION is (a) True

Best explanation: Yes, UNIX PROVIDES us a feature that two users can login with the same USERNAME at the same TIME on the same network host.

Right choice is (d) un-send mails

For explanation I WOULD say: mailx command can perform VARIOUS functions apart from SENDING and receiving emails such as replying to the sender and all recipients, forward it to OTHERS, save it to a different folder, delete it, print it. To view received emails, simply type mailx command and hit ENTER.

The correct answer is (B) RECORDING our session

To explain I would say: script COMMAND is basically used for recording our login session in a file. All the keystrokes, output, ERROR messages that are encountered while our session will be stored in a file which we can view LATER. The name of the file in which the session is stored is typescript.

Correct ANSWER is (a) True

Explanation: Since UNIX is a multiuser system, so communication between systems seems to be natural and important. For this purpose MAILX command is used. Through mailx command, we can SEND and receive emails to different users on same host network or different network. The addressing scheme USES a combination of username and machine name. For example,

The correct choice is (a) as a calculator

Easy explanation: BC command is used for invoking calculator on UNIX SYSTEM. It comes with a WIDE library for performing CALCULATIONS. The power of this tool can be derived from the fact, that it can PERFORM calculations up to and above 900 digits!

The correct answer is (b) -a

To elaborate: SCRIPT command OVERWRITES any previous typescript that may EXIST. -a option allows us to append our session to the existing typescript file without overwriting to it.

 For EXAMPLE,script-a

 We can also record our session to a different log file by USING the following command.

Correct choice is (b) printf

The explanation is: printf command is AVAILABLE on most UNIX systems and it behaves MUCH like a SUBSTITUTION for echo command. It SUPPORTS many of the formats which are used by C’s printf function. printf is also an EXTERNAL command.

Correct answer is (a) special characters beginning with a \ (backslash)

Explanation: An escape sequence is generally a TWO character string which begins with a \. The role of escape sequences is that they change the state of COMPUTER or the peripheral DEVICES attached to it, For example, \n is an escape sequence which IMPLIES a new LINE character.

Correct option is (C) date+”%d/%m/%Y”

Explanation: Date COMMAND can use format SPECIFIERS as arguments with each specifiers PRECEDING with a + , followed by % operator and a single CHARACTER for describing the format.

Right answer is (c) displaying diagnostic messages

Easy explanation: ECHO command is generally used for displaying diagnostic messages on to the terminal or to ISSUE prompt for READING the user input. All shells now have echo built in i.e. it is an internal command.

Right choice is (a) special characters having predefined meaning to the shell

To EXPLAIN: meta-characters are special characters having a predefined meaning to the shell. They are used as wild CARDS for special purposes like PATTERN matching, OUTPUT redirecting etc. *, |, < are meta-characters.

The CORRECT answer is (a) display information about users who are currently logged in.

To explain: who command OUTPUT the DETAILS of the users who are currently logged in to the system. The output includes username, terminal name (on which they are logged in), date and TIME of their LOGIN etc.

Correct answer is (a) date and cal

Best explanation: date command is USED for DISPLAYING the CURRENT system date and time while cal command is used to see the calendar of any specific month/year.

Right choice is (d) man

The explanation is: UNIX provides US with a facility of man command, which is used for getting documentation of any command. For example, to SEEK help on wc command simply type man wc. This will simply display all the possible operations, options, description, synopsis of wc command. The POSIX specification requires only one available option with man command i.e.-k, which prints a one-line description of the command. whatis command is ALSO available on many UNIX systems which also DISPLAYS a one-line description of the command. man -F emulates the behavior of whatis command.

Correct option is (a) using ;

The BEST I can explain: UNIX allows us to specify more than one command at the same TIME in the command line. To do so, we have to separate each command from each other using (;). For EXAMPLE, WC file1 ;ls-l file1 . The > symbol allows us to redirects the output of the command(s). For example, wc file1 > file2. Now, file2 will CONTAIN the output produced by the wc file1 command. Both ; and > are called metacharacters.

Right option is (a) True

The best EXPLANATION: Arguments are parameters which are specified ALONG with commands so that the command can perform an operation or take input from that parameter while options are also arguments but they are predetermined i.e. they perform a particular task. For EXAMPLE, echo hello. In this command hello is an argument while in ls– l, -l is an option.

Correct CHOICE is (a) True

For EXPLANATION: When we specify a command, the SHELL searches for that command in the list of directories specified in the PATH VARIABLE and then executes it after locating the command successfully.

Correct option is (C) uname

Explanation: uname command is used for extracting the details LIKE name, version of the operating system running on the machine. the cd command is used for CHANGING directories and echo command is used for displaying the contents of a string on to the OUTPUT STREAM. wc command is used for counting words and other details in a file.

Correct option is (a) specific instructions for performing a PARTICULAR task

Explanation: COMMANDS are basically specific instructions which are given by the users to perform a particular piece of a task. In UNIX, commands are entered by the USER through a command line interface which further is PROCESSED by the command interpreter i.e. Shell.

The correct option is (a) X WINDOW system

The explanation: The X window system, COMMONLY known as X, is a WINDOWING system developed at MIT. It is an open-source, network TRANSPARENT, client-server based system that PROVIDES a Graphical user interface. X is primarily used on UNIX variants but it is also available for other operating systems also.

Right CHOICE is (a) system manager

Best explanation: A superuser (root) is the UNIX system manager which can PERFORM special tasks like killing any executing program, resetting other users PASSWORDS, change users permissions and performing other system management tasks. The administrator can switch to superuser by ISSUING su command.

The correct CHOICE is (a) Kernel

For EXPLANATION I would SAY: The kernel is the core of the operating system. It is a collection of routines written in C which directly communicates with the hardware. User programs that need to interact with the hardware ACCESS the services of the kernel. There is only ONE kernel running on a system, unlike shells which can be multiple.

Correct OPTION is (a) True

Easy EXPLANATION: COMPUTERS don’t have any capability of translating commands into actions. To do so we REQUIRE shell-a command interpreter which translates our commands into actions. It is actually the interface between the user and kernel. There could be MULTIPLE shells in action on a single system.

Correct choice is (a) True

To EXPLAIN I would say: POSIX- Portable OPERATING System Interface for Computer Environment is basically a set of standards SPECIFIED by IEEE for establishing compatibility between operating systems, especially which are UNIX based. For example, if we write a program relying on POSIX standards, we can EASILY port it AMONG a large family of Unix derivatives (including Linux).

Correct CHOICE is (c) UNIX was not written in ‘C’ language

Easy explanation: One of the most attractive features of UNIX is that it supports multi-user and multitasking ENVIRONMENT which makes it so popular among its users. There are many UNIX variants available in the market. Solaris Unix, AIX, HP Unix, BSD are some of the EXAMPLES. Linux is also a flavor of UNIX which is freely available. Unix was developed in 1969 by AT&T employees Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna at BELL Labs and was written in ‘C’.

Correct choice is (c) GRAPHICAL user interface

The best EXPLANATION: The kernel is the HEART of the operating system while the SHELL is the utility which processes our requests. While system calls are a handful of functions which are used to interact with the kernel and make available the services provided by the operating system. A Graphical user interface (GUI) is available in UNIX, but the traditional UNIX interface is the command LINE only.

Correct answer is (d) C

For explanation I would SAY: UNIX was originally WRITTEN in Assembly language but Dennis Ritchie and Ken THOMPSON wanted an operating system which could run on more than one type of hardware. So in 1973, they rewrote the whole operating system in C language due to which one of the strongest features i.e. PORTABILITY was added to the operating system.

The correct answer is (d) EASY to use

Best EXPLANATION: UNIX is a multitasking operating system i.e. a USER can run multiple tasks concurrently. Similarly, it is a MULTIUSER system because it permits working with multiple users on a single operating system. But a major disadvantage of UNIX lies in the fact that the richness provided by its commands requires a SPECIAL type of commitment to understand the subject. i.e. the user must be well aware of commands he is using and the functions performed by them.

The correct option is (a) an operating system

For explanation I would say: UNIX is an operating system developed in the early 1970’s at Bell LABS by Dennis Ritchie, Ken Thompson, and others. It is a MULTIUSER, multitasking and timesharing operating system. The power of UNIX is DERIVED from its commands and their MULTIPLE options.