UNIX OPERATING SYSTEM QUE&ANS

Q.1  How are Devices are represented in UNIX?

Answer. All devices are represented by files called specified file that are located in /dev directory. Thus, device file and other file are named and accessed in the same way. A 'regular file' is just an oridnary data file in the disk. 'A block special file' represents a device with characteristics similar to a disk. A 'Character special file' represents a device with charactersitics similar to a keyboard.

Q.2- What is Inode?

Answer- All unix file have its description stored in a structure called 'Inode'.The Indoe contains info about the file size, Location,Time of last access, time of last modification etc. Directories are also represented as file and have an asssociated indoe. In addition to description about the file, the inode contains pointer to the data block of the file. If the file is large indode has indirect pointer to a block of pointers to additional data block.A block is typicaly 8K.

Q.3- What is a Shell?

Answer- A shell is an interactive user interface to an operating system service that allow an user to enter commands as character string or through a graphical user interface. The Shell converts them to system call to the os or fork off a process to excute the command. system call results and other information from the OS are represented to the user through an interactive interface. Commonaly used shell are the following.
  SH, CSH, KS.

Q.4- What is Zombie?

Answer- When a program forks and the child finishes before the parent, the kernel still keeps some of its information about the child in case the parent might neeed it.

Q.5 How can get/set environment variable from a program?

Answer- Getting the value of an environment variable is done by using 'getenv()'.
               Setting the value of an environment variable is done by using 'Putenv()'.

Smartphone Safety

Smartphone Safety 
Mobile phones mainly came with the traditional SMS and Call features. With the advent of the mobile Internet or the ability to access the World Wide Web through a phone, the risks that smartphone users face have increased. Regularly use of smartphone for surfing the Internet, downloading music and social networking apart from making calls. From private photos to videos and financial information along with a lot of information on our Contacts, there is plenty on phones that could be misused in the wrong hands.

Steps for Smartphone Safety

1.Security Software- Use security software to protect your phone from malware attacks. Most malware apps also come with anti-theft options for your device. For example, you could use the McAfee Mobile Security.
2. Management of Settings- Explore the settings on your phone and customize them for location reporting, app installation, tracking online behaviour and also Wi-Fi Networking. Selecting strict options in settings allows you to fend off undesirable access to your personal information.
3. App Review- Avoid downloading apps that are not hosted at reputed app stores. If you download them from untested sites they may infect your phone with malware. When installing apps carefully review the terms and conditions of use to determine if you are giving access to information you don’t want to share.
 4.  Restriction of Access - Lock your phone with a PIN Code or Pattern Lock. This ensures that even if your phone is stolen, the thief cannot immediately access information on it. You can then use security software to even remotely ‘wipe off’ or delete information on your phone.
5.Turn Off Public Wi-Fi - Do not use public Wi-Fi to shop or access emails. Public Wi-Fi hotspots can give hackers easy access to your phone. Use your network provider connection as it is much more secure.