3i Infotech Papers: Sample Questions 216 - 217 of 1245

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Question number: 216

» Basic CS » Networks

Short Answer Question▾

Write in Short

What is NVT (Network Virtual Terminal)?

Explanation

Computer network of virtual terminal.

Computer Network of Virtual Terminal.

Computer network of virtual terminal.

  • Network Virtual Terminal (NVT) is just a representation of a basic terminal providing standard for Telnet connection.

  • Software rules which define how data and commands are sent across the network allowing interoperability between Telnet and heterogeneous computers and operating systems.

  • For example, in above figure TELNET client translates characters from the local terminal into NVT.

  • TELNET server translates data and commands from NVT to form acceptable by the remote computer.

  • Useful for testing, making sure conventions are handled by software ensuring that other servers and clients are doing the same.

Question number: 217

» Database » Oracle

True-False▾

Question

Is the Following Statement True or False?

A column defined as PRIMARY KEY can have NULL’s

Answer

FALSE

Explanation

Understanding of primary key constrain

Understanding of Primary Key Constrain

Understanding of primary key constrain

  • Column defined as PRIMARY KEY cannot be null because primary key and unique key can both be used for uniquely identifying a row and unique key can have null value once.

  • PRIMARY KEY indicates a column or group of columns used as a unique identifier for rows in the table.

  • A unique constraint does not by itself it is provide a unique identifier because it does not exclude null value.

  • Primary key should be UNIQUE because a primary key identifies rows in a table so 2 different rows should not have the same key.

  • Use for PRIMARY KEY may be as foreign key in other table.

  • A primary key is cannot be null.