Computer Network Questions and Answers

Answer: B

Correct answer: 45

One full-duplex line serves both directions between a pair, and no line joins a station to itself:

\[ \binom{10}{2} = 45 \]

Answer: D

Correct answer: both (a) and (b)

A time-slot interchanger and a TDM bus both switch by moving samples between time slots rather than by making a physical path, so both are time-division switches. A crosspoint makes a path and is space-division.

Answer: B

Correct answer: half-duplex

A single railway track carries traffic both ways but only one way at a time, which is the definition of half duplex.

Answer: A

Correct answer: False

A combinational circuit has no memory: its output at any moment is determined entirely by the inputs present at that moment. Circuits whose output also depends on past inputs are sequential, and they achieve it with flip-flops.

Answer: A

Correct answer: VDR

RTS, CTS and DSR are all RS-232-C control signals - request to send, clear to send and data set ready. VDR is not among the standard's signals.

Answer: B

Correct answer: dc supply voltage and the average supply current

Power dissipation is

\[ P_D = V_{CC}\times I_{CC(avg)} \]

The average current is used because the current drawn varies as the gate switches; the peak value would overstate the power, and the supply is dc, not ac.

Answer: D

Correct answer: 4

A binary counter with \( n \) flip-flops passes through \( 2^{n} \) distinct states, so a modulus-16 counter needs \[ 2^{n} = 16 \quad\Rightarrow\quad n = 4. \] Each flip-flop stores one bit, and four bits represent the sixteen values 0000 to 1111 - decimal 0 to 15. The general rule is worth remembering in both directions: for a required modulus \( N \), the number of flip-flops is the smallest \( n \) with \( 2^{n} \ge N \). A decade counter of modulus 10 therefore still needs four flip-flops, and the six unused states are removed by feedback that resets the counter at a count of ten. Counters divide as well as count: a modulus-16 counter’s most significant output is the clock frequency divided by 16, which is why they are used as frequency dividers. An asynchronous or ripple counter clocks each stage from the previous one and is simpler but slower; a synchronous counter clocks every stage together and avoids the accumulated delay.

Answer: A

Correct answer: 5-7

In a network user address the first four digits are the DNIC, digits 5 to 7 the area, and 8 to 12 the terminal.

Answer: A

Correct answer: simplify Boolean expressions

A Karnaugh map arranges a truth table so that adjacent cells differ in one variable, letting groups of ones be combined by inspection. It is a visual substitute for repeated algebraic manipulation.

Answer: D

Correct answer: ALU

The arithmetic logic unit carries out arithmetic operations such as addition and subtraction and logical operations such as AND, OR, NOT and XOR, together with shifts and comparisons. It is one of the three parts of the central processing unit, the others being the control unit, which fetches and decodes instructions and directs the rest of the machine, and the registers, which hold the operands and results the ALU works on. Alongside its result the ALU sets flag bits - zero, carry, sign and overflow - and those flags are what conditional branch instructions test, which is how a program makes decisions. RAM and ROM are memory and store data rather than operate on it, and a bus is a set of parallel conductors carrying data, addresses or control signals between components. Subtraction inside the ALU is performed as addition of the 2’s complement, which is why no separate subtractor is needed.