Basic CS [3i Infotech Placement]: Sample Questions 236 - 237 of 243

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Question 236

Basic CS

Describe in Detail


What is the header length of Ether Net MAC?


The Ether Net MAC

The basic MAC data frame format for Ethernet used within the 10 and 100 Mbps systems is given above.

Mac header has following fields:

  • The first two fields are 6-byte source and destination address.
  • The last field is the 2-byte field length, which gives the length of the data field.
  • Because Ethernet has variable length data fields, their length needs to be known for the receiver to know where the frame ends.
  • The third field is the 4-byte virtual LAN tag.
  • When in use, the first two bytes are set 81 - 00 which tells the receiver that the VLAN tag field is being used.

Question 237



The standard source for standard input, standard output and standard error is


Choice (4)


The terminal


/usr/you/input, /usr/you/output/, /usr/you/error respectively




Question does not provide sufficient data or is vague




Understanding of Standard Output and Standard Error

The standard source for standard input, standard output and standard error is the terminal.

Standard Output

  • Program sends information to standard output even without knowing.
  • However, the same output can go to a printer, an ordinary file, or the network.

Standard Input

  • Program gets its information from standard input which by is the keyboard.
  • Program never “knows” where the information comes from.
  • Standard input can also come from a file or network.

Standard Error

In addition to standard input and standard output, a running program sends error messages, which by default, the shell directs to the screen.

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