To interface a computer terminal with a modem, required physical layer standard is
Answer: D
Correct answer: Either (b) or (c)
Both RS-232-C and RS-449 are physical-layer standards for the interface between a terminal and a modem; RS-449 was introduced to carry higher rates over longer distances, but either will serve.
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Simple network management protocol (SNMP) is implemented with a daughter board in
Answer: C
Correct answer: the hubs
SNMP management is put where the traffic converges, so the agent is fitted to the hub, which sees every port on its segment. Putting it on a single node or PC would show only that machine's view.
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The NAND gate is functionally complete, so any Boolean function can be built using NAND gates alone.
Answer: B
Correct answer: True
NAND is functionally complete: a NOT is a NAND with its inputs tied together, an AND is a NAND followed by that inverter, and an OR follows from De Morgan’s theorem. NOR is the other functionally complete gate.
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The hexadecimal number system uses which base?
Answer: C
Correct answer: 16
Hexadecimal is base 16, using the digits 0 to 9 followed by the letters A to F for the values 10 to 15. It is used because each hexadecimal digit corresponds to exactly four bits, so binary can be written compactly and converted by inspection rather than by arithmetic. The byte 11010110 splits into 1101 and 0110, which are D and 6, giving D6. Octal, base 8, works the same way with three bits per digit, and was common in the era of 12-, 24- and 36-bit machines; hexadecimal took over once 8-, 16- and 32-bit words became standard, since those divide evenly by four. Hexadecimal is written with a prefix to avoid ambiguity: 0x in C and its descendants, or a trailing H in assembly. It appears throughout computing - memory addresses, colour codes such as #FF0000 for red, and MAC addresses are all hexadecimal.
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A NOR gate produces a HIGH output only when all of its inputs are LOW.
Answer: B
Correct answer: True
The statement is true. A NOR gate is an OR gate followed by an inverter, so its output is the complement of OR: since OR gives 0 only when every input is 0, NOR gives 1 only in that case. Its truth table for two inputs runs: 0,0 gives 1; 0,1 gives 0; 1,0 gives 0; 1,1 gives 0. NOR is a universal gate: every logic function can be built from NOR gates alone. Tying both inputs together makes an inverter; a NOR followed by an inverting NOR makes an OR; and by De Morgan’s theorem a NOR fed by two inverters makes an AND. NAND is universal for the same reason. The first integrated circuit computer, the Apollo Guidance Computer, was built almost entirely from three-input NOR gates - a practical demonstration of universality. Two cross-coupled NOR gates also form the simplest SR latch, the basic one-bit memory element.
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In stop-and-wait ARQ, if data 1 has an error, then receiver sends which frame ?
Answer: D
Correct answer: NAK
Stop-and-wait ARQ has only one frame outstanding at a time, so a negative acknowledgement needs no sequence number: there is only one frame it could refer to. Numbered NAKs belong to the sliding-window protocols.
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Method of communication in which transmission takes place in both directions, but only in one direction at a time, is called
Answer: D
Correct answer: half duplex
Half duplex allows both directions but only one at a time, so the line must be turned round between transmissions. Full duplex allows both at once and simplex only one direction ever.
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How many inputs does a full adder have ?
Answer: D
Correct answer: Three
A full adder takes three inputs - the two bits being added and a carry-in from the previous stage - and produces a sum and a carry-out. That carry-in is exactly what a half adder lacks, which is why half adders cannot be chained.
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How many digits of the DNICC (Data Network Identiication Code) identify the country ?
Answer: A
Correct answer: First three
The first three digits of the DNIC are the country code; the fourth distinguishes networks within that country.
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A high speed communication equipment typically would not be needed for
Answer: A
Correct answer: E-mail
A mail message is small and its delivery is not time-critical, so it travels perfectly well over a slow link. Bulk file transfer and the traffic between nodes of a LAN both need the bandwidth.
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