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BECIL MCQs

Practice BECIL-oriented Electronics & Telecommunication Engineering MCQs with answers and explanations for technical exam preparation. Questions are arranged in pages of up to 100.

Question 1201
Computer & Networking BasicsIPv4 Addressing

Which of the following is a valid IPv4 address?

  • A192.168.1.25
  • B192.168.300.1
  • C10.10.10.256
  • D172.16.1
Report an error
Correct Answer: A. 192.168.1.25
Explanation: Each IPv4 octet must be in the range 0 through 255 and the usual dotted-decimal form contains four octets.
Reference: Standard computer networking fundamentals: ipv4 addressing
Question 1205
Computer & Networking BasicsSubnetting

For the network 192.168.10.0/24, the conventional broadcast address is?

  • A192.168.10.0
  • B192.168.10.1
  • C192.168.10.254
  • D192.168.10.255
Report an error
Correct Answer: D. 192.168.10.255
Explanation: With a /24 prefix, the final 8 bits are host bits; setting all of them to 1 gives 192.168.10.255.
Reference: Standard computer networking fundamentals: subnetting
Question 1206
Computer & Networking BasicsMAC Addressing

A MAC address is primarily associated with which OSI layer?

  • APhysical layer only
  • BData Link layer
  • CNetwork layer
  • DTransport layer
Report an error
Correct Answer: B. Data Link layer
Explanation: MAC addresses are used for Layer-2 frame delivery on technologies such as Ethernet.
Reference: Standard computer networking fundamentals: mac addressing
Question 1207
Computer & Networking BasicsMAC Addressing

A conventional Ethernet MAC address is how many bits long?

  • A32 bits
  • B48 bits
  • C64 bits
  • D128 bits
Report an error
Correct Answer: B. 48 bits
Explanation: Standard Ethernet MAC addresses are 48 bits, commonly written as six hexadecimal octets.
Reference: Standard computer networking fundamentals: mac addressing
Question 1208
Computer & Networking BasicsARP

ARP in IPv4 is used to determine a device’s?

  • AMAC address corresponding to a known local IPv4 address
  • BDomain name from an email address
  • CTCP port from a URL only
  • DSubnet mask from a password
Report an error
Correct Answer: A. MAC address corresponding to a known local IPv4 address
Explanation: ARP resolves an IPv4 address to the corresponding link-layer MAC address on the local network.
Reference: Standard computer networking fundamentals: arp
Question 1209
Computer & Networking BasicsDNS

DNS is primarily used to?

  • ATranslate domain names into IP addresses and provide related naming records
  • BAssign MAC addresses to switches
  • CRegenerate weak electrical signals
  • DEncrypt hard disks
Report an error
Correct Answer: A. Translate domain names into IP addresses and provide related naming records
Explanation: The Domain Name System maps human-readable names to IP addresses and stores other DNS resource records.
Reference: Standard computer networking fundamentals: dns
Question 1210
Computer & Networking BasicsDHCP

DHCP is commonly used to automatically provide hosts with?

  • AIP configuration parameters
  • BCPU instructions
  • CMAC addresses manufactured into NICs
  • DWeb page source code
Report an error
Correct Answer: A. IP configuration parameters
Explanation: DHCP can dynamically supply IP address, subnet mask, default gateway, DNS-server information and other network parameters.
Reference: Standard computer networking fundamentals: dhcp
Question 1214
Computer & Networking BasicsPorts

A transport-layer port number primarily identifies?

  • AAn application or process endpoint on a host
  • BA physical switch connector only
  • CA router's power supply
  • DA cable length
Report an error
Correct Answer: A. An application or process endpoint on a host
Explanation: TCP and UDP ports allow incoming traffic to be delivered to the appropriate application/process endpoint.
Reference: Standard computer networking fundamentals: ports
Question 1217
Computer & Networking BasicsApplication Protocols

SMTP is primarily used for?

  • ASending and relaying email
  • BResolving MAC addresses
  • CAssigning IP addresses
  • DTransferring Ethernet frames between switches only
Report an error
Correct Answer: A. Sending and relaying email
Explanation: SMTP is the standard application-layer protocol used to submit and relay email messages.
Reference: Standard computer networking fundamentals: application protocols
Question 1218
Computer & Networking BasicsApplication Protocols

FTP is designed primarily for?

  • AFile transfer
  • BDomain-name resolution
  • CAutomatic IP assignment
  • DClock synchronization only
Report an error
Correct Answer: A. File transfer
Explanation: FTP stands for File Transfer Protocol and is designed for transferring files between networked systems.
Reference: Standard computer networking fundamentals: application protocols
Question 1219
Computer & Networking BasicsNetwork Topologies

In a star topology, end devices are typically connected to?

  • AA central device such as a switch
  • BEvery other node with a dedicated cable
  • CA single unbroken bus only
  • DNo central connection point
Report an error
Correct Answer: A. A central device such as a switch
Explanation: A star topology connects each endpoint to a central hub or, more commonly today, an Ethernet switch.
Reference: Standard computer networking fundamentals: network topologies
Question 1220
Computer & Networking BasicsNetwork Topologies

In a bus topology, all nodes traditionally share?

  • AA common backbone communication medium
  • BA separate central switch port each
  • CA dedicated point-to-point link to every other node
  • DAn individual router to the Internet
Report an error
Correct Answer: A. A common backbone communication medium
Explanation: A classic bus network uses a shared backbone cable to which nodes are attached.
Reference: Standard computer networking fundamentals: network topologies
Question 1222
Computer & Networking BasicsEthernet Switching

A basic Ethernet switch reduces unnecessary frame delivery compared with a hub by learning?

  • ASource MAC addresses and associated ports
  • BApplication passwords
  • CCPU register values
  • DDNS zone files only
Report an error
Correct Answer: A. Source MAC addresses and associated ports
Explanation: A switch builds a MAC address table from source addresses and uses it to forward known unicast frames only toward the appropriate destination port.
Reference: Standard computer networking fundamentals: ethernet switching
Question 1223
Computer & Networking BasicsIP Addressing

Which of the following IPv4 address ranges is private?

  • A10.0.0.0/8
  • B8.0.0.0/8
  • C100.0.0.0/8
  • D200.0.0.0/8
Report an error
Correct Answer: A. 10.0.0.0/8
Explanation: 10.0.0.0/8 is one of the IPv4 address blocks reserved for private networks.
Reference: Standard computer networking fundamentals: ip addressing
Question 1224
Computer & Networking BasicsIP Addressing

Which address is within the private IPv4 block 172.16.0.0/12?

  • A172.15.1.1
  • B172.20.1.1
  • C172.32.1.1
  • D173.16.1.1
Report an error
Correct Answer: B. 172.20.1.1
Explanation: The private 172.16.0.0/12 range extends from 172.16.0.0 through 172.31.255.255.
Reference: Standard computer networking fundamentals: ip addressing
Question 1225
Computer & Networking BasicsIP Addressing

Which IPv4 range is reserved for loopback testing?

  • A127.0.0.0/8
  • B169.254.0.0/16
  • C224.0.0.0/4
  • D192.0.2.0/24
Report an error
Correct Answer: A. 127.0.0.0/8
Explanation: IPv4 addresses in 127.0.0.0/8 are reserved for loopback; 127.0.0.1 is commonly used as localhost.
Reference: Standard computer networking fundamentals: ip addressing
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Question 1226
Computer & Networking BasicsIPv6

IPv6 addresses are how many bits long?

  • A32
  • B64
  • C128
  • D256
Report an error
Correct Answer: C. 128
Explanation: IPv6 uses 128-bit addresses, providing a much larger address space than IPv4.
Reference: Standard computer networking fundamentals: ipv6
Question 1227
Computer & Networking BasicsIPv6

Which notation is normally used to write IPv6 addresses?

  • AEight groups of hexadecimal values separated by colons
  • BFour decimal octets only
  • CSix binary groups separated by commas
  • DA single 32-bit decimal number
Report an error
Correct Answer: A. Eight groups of hexadecimal values separated by colons
Explanation: IPv6 addresses are normally represented as hexadecimal groups separated by colons, with permitted compression rules.
Reference: Standard computer networking fundamentals: ipv6
Question 1228
Computer & Networking BasicsIPv6

The IPv6 loopback address is?

  • A::1
  • B::
  • C127.0.0.1
  • DFF:FF:FF:FF:FF:FF
Report an error
Correct Answer: A. ::1
Explanation: IPv6 reserves ::1 as the loopback address.
Reference: Standard computer networking fundamentals: ipv6
Question 1229
Computer & Networking BasicsSubnetting

A /26 IPv4 subnet contains how many total addresses?

  • A32
  • B64
  • C128
  • D256
Report an error
Correct Answer: B. 64
Explanation: A /26 prefix leaves 6 host bits, so the subnet contains 2^6=64 total addresses.
Reference: Standard computer networking fundamentals: subnetting
Question 1231
Computer & Networking BasicsSubnetting

The subnet mask corresponding to /26 is?

  • A255.255.255.0
  • B255.255.255.128
  • C255.255.255.192
  • D255.255.255.224
Report an error
Correct Answer: C. 255.255.255.192
Explanation: A /26 mask has 26 leading 1 bits, giving 255.255.255.192.
Reference: Standard computer networking fundamentals: subnetting
Question 1232
Computer & Networking BasicsSubnetting

For the subnet 192.168.1.64/26, the broadcast address is?

  • A192.168.1.63
  • B192.168.1.64
  • C192.168.1.126
  • D192.168.1.127
Report an error
Correct Answer: D. 192.168.1.127
Explanation: A /26 block has 64 addresses. The block beginning at .64 ends at .127, which is its broadcast address.
Reference: Standard computer networking fundamentals: subnetting
Question 1233
Computer & Networking BasicsSubnetting

For 192.168.1.64/26, the conventional usable host range is?

  • A192.168.1.64 to 192.168.1.127
  • B192.168.1.65 to 192.168.1.126
  • C192.168.1.1 to 192.168.1.62
  • D192.168.1.128 to 192.168.1.191
Report an error
Correct Answer: B. 192.168.1.65 to 192.168.1.126
Explanation: The network address is .64 and broadcast is .127, leaving .65 through .126 for conventional host assignment.
Reference: Standard computer networking fundamentals: subnetting
Question 1234
Computer & Networking BasicsDefault Gateway

A host normally sends traffic to its default gateway when the destination is?

  • AOutside the host's local IP subnet
  • BIts own loopback address
  • CThe same host's RAM
  • DAlways on the same Ethernet port
Report an error
Correct Answer: A. Outside the host's local IP subnet
Explanation: The default gateway is the router used to reach destinations not directly on the local subnet.
Reference: Standard computer networking fundamentals: default gateway
Question 1235
Computer & Networking BasicsNAT

NAT is commonly used at an IPv4 network edge to?

  • ATranslate between private and public address information
  • BConvert MAC addresses into passwords
  • CIncrease CPU clock frequency
  • DReplace Ethernet frames with analog audio
Report an error
Correct Answer: A. Translate between private and public address information
Explanation: Network Address Translation commonly allows privately addressed hosts to communicate through public IPv4 addressing at the network boundary.
Reference: Standard computer networking fundamentals: nat
Question 1236
Computer & Networking BasicsNAT

PAT allows multiple private hosts to share a public IPv4 address primarily by distinguishing connections using?

  • ATransport-layer port numbers
  • BMonitor resolutions
  • CCable lengths
  • DCPU opcodes
Report an error
Correct Answer: A. Transport-layer port numbers
Explanation: Port Address Translation tracks flows using address and transport-port information so many internal connections can share one public address.
Reference: Standard computer networking fundamentals: nat
Question 1237
Computer & Networking BasicsICMP

ICMP is commonly used for?

  • ANetwork-layer error reporting and diagnostic messages
  • BWeb-page formatting
  • CEmail storage
  • DFile compression
Report an error
Correct Answer: A. Network-layer error reporting and diagnostic messages
Explanation: ICMP carries control, error and diagnostic information for IP networks.
Reference: Standard computer networking fundamentals: icmp
Question 1239
Computer & Networking BasicsNetwork Diagnostics

Traceroute or tracert primarily helps determine?

  • AThe sequence of Layer-3 hops toward a destination
  • BThe CPU cache size of a remote host
  • CThe physical length of every Ethernet cable
  • DA user's password
Report an error
Correct Answer: A. The sequence of Layer-3 hops toward a destination
Explanation: Traceroute exploits IP hop-limit/TTL behavior and returned control messages to reveal routers along a path.
Reference: Standard computer networking fundamentals: network diagnostics
Question 1240
Computer & Networking BasicsRouting

A router decreases an IPv4 packet’s TTL field when?

  • AForwarding the packet to the next hop
  • BReceiving a local keyboard input
  • CWriting data to RAM
  • DResolving a DNS name only
Report an error
Correct Answer: A. Forwarding the packet to the next hop
Explanation: Each router forwarding an IPv4 packet decrements TTL, helping prevent packets from circulating indefinitely.
Reference: Standard computer networking fundamentals: routing
Question 1241
Computer & Networking BasicsRouting

A routing table is used by a router to choose?

  • AA next hop or outgoing interface for a destination network
  • BA user's application password
  • CA switch's power rating
  • DThe CPU instruction set
Report an error
Correct Answer: A. A next hop or outgoing interface for a destination network
Explanation: Routers compare destination IP addresses with routing-table prefixes to determine how packets should be forwarded.
Reference: Standard computer networking fundamentals: routing
Question 1242
Computer & Networking BasicsRouting

When multiple routing-table entries match an IP destination, routers generally prefer the route with the?

  • ALongest matching prefix
  • BShortest matching prefix in every case
  • CLargest physical cable
  • DLowest destination IP address
Report an error
Correct Answer: A. Longest matching prefix
Explanation: Longest-prefix matching selects the most specific matching network route.
Reference: Standard computer networking fundamentals: routing
Question 1243
Computer & Networking BasicsVLAN

A VLAN is used to create separate logical?

  • ALayer-2 broadcast domains
  • BCPU cores
  • CInternet domain names
  • DPhysical-layer voltages
Report an error
Correct Answer: A. Layer-2 broadcast domains
Explanation: VLANs logically segment a switched Ethernet network into distinct Layer-2 broadcast domains.
Reference: Standard computer networking fundamentals: vlan
Question 1244
Computer & Networking BasicsEthernet Switching

On a switch, each individual switch port normally forms a separate?

  • ACollision domain
  • BIP broadcast domain regardless of VLAN
  • CAutonomous system
  • DDNS zone
Report an error
Correct Answer: A. Collision domain
Explanation: Modern switched Ethernet gives each port its own collision domain, unlike a shared hub segment.
Reference: Standard computer networking fundamentals: ethernet switching
Question 1245
Computer & Networking BasicsVLAN

Devices in different VLANs normally require what to communicate at the IP layer?

  • AInter-VLAN routing
  • BOnly a passive hub
  • CA crossover cable with no Layer-3 function
  • DNo networking device
Report an error
Correct Answer: A. Inter-VLAN routing
Explanation: Communication between separate VLAN IP networks requires a Layer-3 device or Layer-3 switching function.
Reference: Standard computer networking fundamentals: vlan
Question 1246
Computer & Networking BasicsWireless Networking

Wi-Fi LAN technologies are primarily standardized under?

  • AIEEE 802.11
  • BIEEE 802.3
  • CIEEE 802.15.4 only
  • DIEEE 754
Report an error
Correct Answer: A. IEEE 802.11
Explanation: The IEEE 802.11 family specifies wireless LAN technologies commonly known as Wi-Fi.
Reference: Standard computer networking fundamentals: wireless networking
Question 1247
Computer & Networking BasicsNetwork Security

A network firewall is primarily used to?

  • AControl network traffic according to security rules
  • BIncrease RAM capacity
  • CConvert binary to decimal
  • DGenerate an antenna carrier
Report an error
Correct Answer: A. Control network traffic according to security rules
Explanation: A firewall permits, blocks or otherwise controls network traffic according to configured security policy and inspection capabilities.
Reference: Standard computer networking fundamentals: network security
Question 1248
Computer & Networking BasicsAdvanced Subnetting

A /27 IPv4 subnet contains how many total addresses?

  • A16
  • B32
  • C64
  • D128
Report an error
Correct Answer: B. 32
Explanation: A /27 prefix leaves 5 host bits, so it contains 2^5=32 total IPv4 addresses.
Reference: Standard computer and networking fundamentals: advanced subnetting
Question 1250
Computer & Networking BasicsAdvanced Subnetting

The subnet mask corresponding to /27 is?

  • A255.255.255.128
  • B255.255.255.192
  • C255.255.255.224
  • D255.255.255.240
Report an error
Correct Answer: C. 255.255.255.224
Explanation: A /27 mask has 27 leading 1 bits, giving 255.255.255.224.
Reference: Standard computer and networking fundamentals: advanced subnetting
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Question 1251
Computer & Networking BasicsEthernet Frames

Ethernet’s FCS field is primarily used for?

  • AError detection in the received frame
  • BIP address assignment
  • CEncryption of the entire frame
  • DRouting between autonomous systems
Report an error
Correct Answer: A. Error detection in the received frame
Explanation: The Frame Check Sequence contains a CRC value used to detect transmission errors in Ethernet frames.
Reference: Standard computer and networking fundamentals: ethernet frames
Question 1252
Computer & Networking BasicsEthernet Switching

A switch receives a unicast Ethernet frame whose destination MAC address is unknown in its MAC table. It normally?

  • AFloods the frame out appropriate ports in the same VLAN except the incoming port
  • BDrops every such frame immediately
  • CSends it only to the default gateway
  • DConverts it into an IP broadcast
Report an error
Correct Answer: A. Floods the frame out appropriate ports in the same VLAN except the incoming port
Explanation: Unknown unicast traffic is normally flooded within the relevant VLAN until the destination location is learned.
Reference: Standard computer and networking fundamentals: ethernet switching
Question 1253
Computer & Networking BasicsEthernet Frames

An Ethernet broadcast frame has which destination MAC address?

  • A00:00:00:00:00:00
  • BFF:FF:FF:FF:FF:FF
  • C01:00:00:00:00:00
  • D127:00:00:00:00:01
Report an error
Correct Answer: B. FF:FF:FF:FF:FF:FF
Explanation: All 48 destination bits are 1 for the Ethernet broadcast address, written FF:FF:FF:FF:FF:FF.
Reference: Standard computer and networking fundamentals: ethernet frames
Question 1254
Computer & Networking BasicsNetwork Segmentation

A Layer-2 switch normally does not forward a broadcast frame across?

  • AA router boundary
  • BPorts within the same VLAN
  • CThe local switch fabric
  • DAn Ethernet link in the same broadcast domain
Report an error
Correct Answer: A. A router boundary
Explanation: Routers separate Layer-2 broadcast domains and do not normally forward Ethernet broadcasts between IP networks.
Reference: Standard computer and networking fundamentals: network segmentation
Question 1255
Computer & Networking BasicsTroubleshooting

If a host can communicate with devices in its own subnet but cannot reach remote IP networks, a likely configuration to check first is the?

  • ADefault gateway
  • BMonitor refresh rate
  • CCPU cache
  • DKeyboard layout
Report an error
Correct Answer: A. Default gateway
Explanation: Local subnet traffic does not require a router, while remote-network traffic normally depends on a correctly configured and reachable default gateway.
Reference: Standard computer and networking fundamentals: troubleshooting
Question 1257
Computer & Networking BasicsDHCP

If a DHCP client cannot obtain a lease, which configuration may it fail to receive automatically?

  • AIP address and related network parameters
  • BFactory-programmed MAC address
  • CCPU instruction set
  • DHard-disk sector size
Report an error
Correct Answer: A. IP address and related network parameters
Explanation: DHCP supplies dynamic IP configuration such as address, mask, gateway and DNS-server information.
Reference: Standard computer and networking fundamentals: dhcp
Question 1258
Computer & Networking BasicsAdvanced Subnetting

For the subnet 10.0.0.96/27, the broadcast address is?

  • A10.0.0.95
  • B10.0.0.96
  • C10.0.0.126
  • D10.0.0.127
Report an error
Correct Answer: D. 10.0.0.127
Explanation: A /27 has blocks of 32 addresses. The block starting at .96 ends at .127, its broadcast address.
Reference: Standard computer and networking fundamentals: advanced subnetting
Question 1263
Computer & Networking BasicsTCP

TCP connection establishment normally uses which sequence?

  • ASYN, SYN-ACK, ACK
  • BACK, FIN, RST
  • CSYN, FIN, ACK
  • DARP, SYN, DNS
Report an error
Correct Answer: A. SYN, SYN-ACK, ACK
Explanation: TCP normally establishes a connection using the three-way handshake SYN → SYN-ACK → ACK.
Reference: Standard computer and networking fundamentals: tcp
Question 1264
Computer & Networking BasicsTCP

In TCP, sequence numbers are mainly used to support?

  • AOrdered delivery and loss detection/retransmission
  • BDomain-name resolution
  • CMAC-address manufacturing
  • DPhysical signal regeneration
Report an error
Correct Answer: A. Ordered delivery and loss detection/retransmission
Explanation: TCP sequence numbers identify byte positions, enabling ordered reassembly and detection/recovery of missing data.
Reference: Standard computer and networking fundamentals: tcp
Question 1265
Computer & Networking BasicsTCP

A TCP acknowledgement primarily indicates?

  • AData successfully received up to an expected sequence point
  • BThe sender's MAC address has changed
  • CA DNS server is unavailable
  • DThe Ethernet cable is shielded
Report an error
Correct Answer: A. Data successfully received up to an expected sequence point
Explanation: TCP acknowledgements communicate reception progress and support reliable delivery.
Reference: Standard computer and networking fundamentals: tcp
Question 1266
Computer & Networking BasicsTCP

If a TCP segment is lost, reliability is commonly achieved by?

  • ARetransmission
  • BChanging the destination MAC permanently
  • CIncreasing the IPv4 address length
  • DDisabling sequence numbers
Report an error
Correct Answer: A. Retransmission
Explanation: TCP can retransmit data when acknowledgements or other loss-detection mechanisms indicate that data was not successfully delivered.
Reference: Standard computer and networking fundamentals: tcp
Question 1267
Computer & Networking BasicsDHCP

A DHCP relay is useful when the DHCP server and client are?

  • AOn different IP subnets
  • BInside the same CPU register
  • CConnected by no network
  • DUsing only loopback addresses
Report an error
Correct Answer: A. On different IP subnets
Explanation: DHCP discovery begins with local broadcasts, so a relay can forward DHCP messages between client and server across router boundaries.
Reference: Standard computer and networking fundamentals: dhcp
Question 1269
Computer & Networking BasicsCybersecurity Fundamentals

Which security property aims to prevent unauthorized alteration of data?

  • AIntegrity
  • BLatency
  • CThroughput
  • DFragmentation
Report an error
Correct Answer: A. Integrity
Explanation: Integrity concerns the correctness and trustworthiness of data and protection against unauthorized modification.
Reference: Standard computer and networking fundamentals: cybersecurity fundamentals
Question 1270
Computer & Networking BasicsCybersecurity Fundamentals

Which security property aims to keep systems and data accessible to authorized users when required?

  • AAvailability
  • BCompression
  • CModulation
  • DAddress resolution
Report an error
Correct Answer: A. Availability
Explanation: Availability is the security objective of maintaining timely and reliable access to systems and information.
Reference: Standard computer and networking fundamentals: cybersecurity fundamentals
Question 1271
Computer & Networking BasicsCybersecurity Fundamentals

Phishing is an attack that commonly attempts to?

  • ATrick users into revealing credentials or other sensitive information
  • BIncrease Ethernet bandwidth
  • CImprove routing convergence
  • DRepair corrupted files automatically
Report an error
Correct Answer: A. Trick users into revealing credentials or other sensitive information
Explanation: Phishing uses deceptive messages or sites to manipulate users into disclosing information or taking unsafe actions.
Reference: Standard computer and networking fundamentals: cybersecurity fundamentals
Question 1272
Computer & Networking BasicsCybersecurity Fundamentals

Using a unique strong password together with multi-factor authentication primarily improves account security by?

  • ARequiring more than one form of evidence and reducing reliance on a password alone
  • BMaking IP addresses unnecessary
  • CEliminating all malware permanently
  • DIncreasing physical cable bandwidth
Report an error
Correct Answer: A. Requiring more than one form of evidence and reducing reliance on a password alone
Explanation: MFA adds an independent authentication factor, so possession of a password alone is less likely to be sufficient for account access.
Reference: Standard computer and networking fundamentals: cybersecurity fundamentals
Question 1273
Digital ElectronicsArithmetic Circuits

A 4-bit binary adder uses identical ripple-carry full-adder stages. If each stage requires 12 ns for its carry output to become valid after carry-in changes, approximately what is the worst-case carry propagation time through all four stages?

  • A12 ns
  • B24 ns
  • C36 ns
  • D48 ns
Report an error
Correct Answer: D. 48 ns
Explanation: In a ripple-carry adder, a carry may propagate serially through all four stages. The approximate worst-case carry delay is 4 × 12 ns = 48 ns.
Reference: Standard digital electronics: ripple-carry adder delay
Question 1274
Digital ElectronicsArithmetic Circuits

The principal purpose of carry look-ahead logic in a binary adder is to?

  • AReduce carry propagation delay
  • BConvert binary to Gray code
  • CStore the carry permanently
  • DReduce the number of sum bits
Report an error
Correct Answer: A. Reduce carry propagation delay
Explanation: Carry look-ahead forms carry signals from generate and propagate terms in parallel, reducing the delay associated with a ripple-carry chain.
Reference: Standard digital electronics: carry look-ahead
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Question 1276
Digital ElectronicsSigned Arithmetic

In two’s-complement signed arithmetic, adding two positive n-bit numbers produces an overflow when?

  • AThe result has sign bit 1 even though both operands have sign bit 0
  • BA carry is produced from the LSB
  • CThe result is zero
  • DThe carry-in to the LSB is 1
Report an error
Correct Answer: A. The result has sign bit 1 even though both operands have sign bit 0
Explanation: Signed overflow occurs when operands with the same sign produce a result with the opposite sign. For two positive operands, a negative-sign result indicates overflow.
Reference: Standard digital electronics: two's-complement overflow
Question 1277
Digital ElectronicsSigned Arithmetic

In two’s-complement addition, overflow can be detected by XORing which two carry signals?

  • ACarry into and carry out of the sign bit
  • BCarry into bit 0 and bit 1
  • CTwo successive clock carries
  • DCarry out and borrow out
Report an error
Correct Answer: A. Carry into and carry out of the sign bit
Explanation: For two's-complement addition, overflow equals the XOR of the carry into the most significant sign bit and the carry out of that bit.
Reference: Standard digital electronics: overflow detection
Question 1278
Digital ElectronicsDigital Interfaces

Which property distinguishes a Schmitt-trigger digital input from an ordinary single-threshold input?

  • AIt has two switching thresholds and hysteresis
  • BIt stores one bit indefinitely
  • CIt always inverts the signal twice
  • DIt requires no supply voltage
Report an error
Correct Answer: A. It has two switching thresholds and hysteresis
Explanation: A Schmitt-trigger input uses different rising and falling switching thresholds, creating hysteresis that improves immunity to slowly varying or noisy inputs.
Reference: Standard digital electronics: Schmitt trigger
Question 1280
Digital ElectronicsDigital Interfaces

Why are tri-state buffers commonly used on a shared digital bus?

  • ATo allow multiple devices to be connected while only one enabled driver controls the bus at a time
  • BTo make every device drive the bus simultaneously
  • CTo convert the bus to analog
  • DTo eliminate the need for logic levels
Report an error
Correct Answer: A. To allow multiple devices to be connected while only one enabled driver controls the bus at a time
Explanation: Disabled tri-state outputs present high impedance, allowing several devices to share conductors while preventing normal operation from having multiple active drivers at once.
Reference: Standard digital electronics: bus interfacing
Question 1281
Digital ElectronicsDigital Interfaces

If two push-pull digital outputs connected to the same bus are simultaneously enabled, one driving HIGH and the other LOW, the condition is called?

  • ABus contention
  • BGray transition
  • CClock skew
  • DDynamic refresh
Report an error
Correct Answer: A. Bus contention
Explanation: Opposing active drivers on the same line create bus contention, potentially causing excessive current and an undefined bus voltage.
Reference: Standard digital electronics: bus contention
Question 1285
Digital ElectronicsLogic Hazards

In a static-1 hazard, the output of a combinational circuit may momentarily do what even though it should remain at logic 1?

  • ARemain permanently LOW
  • BDrop briefly to logic 0
  • COscillate indefinitely
  • DBecome high-impedance
Report an error
Correct Answer: B. Drop briefly to logic 0
Explanation: A static-1 hazard is an unwanted 1→0→1 glitch caused by unequal propagation delays along different logic paths.
Reference: Standard digital electronics: static hazards
Question 1287
Digital ElectronicsFinite State Machines

For the same behavioral specification, a Mealy state machine can often use fewer states than an equivalent Moore machine because?

  • AIts outputs may respond directly to inputs as well as state
  • BIt contains no combinational logic
  • CIt does not use a clock
  • DIt stores multiple analog levels
Report an error
Correct Answer: A. Its outputs may respond directly to inputs as well as state
Explanation: Because Mealy outputs can depend directly on current inputs, some output distinctions that require separate Moore states can be represented without adding states.
Reference: Standard digital electronics: FSM realization
Question 1288
Digital ElectronicsError Detection Codes

A parity system using one parity bit can reliably detect which class of errors in a transmitted word?

  • AAny odd number of bit errors
  • BEvery even number of bit errors
  • CAll burst errors regardless of length
  • DEvery possible error pattern
Report an error
Correct Answer: A. Any odd number of bit errors
Explanation: A single parity check changes whenever an odd number of bits are inverted, so all odd-number error patterns are detected; even-number patterns can escape detection.
Reference: Standard digital electronics: parity
Question 1290
Digital ElectronicsError Control Codes

A standard Hamming code with minimum Hamming distance dmin=3 can?

  • ACorrect one bit error but not guarantee correction of two bit errors
  • BCorrect any two bit errors
  • CCorrect any three bit errors
  • DOnly detect one bit error and correct none
Report an error
Correct Answer: A. Correct one bit error but not guarantee correction of two bit errors
Explanation: A code with dmin=3 can correct floor((dmin−1)/2)=1 error. It can detect up to two errors, but ordinary Hamming decoding cannot reliably correct two.
Reference: Standard digital electronics: Hamming distance
Question 1291
Digital ElectronicsProgrammable Logic Devices

In a programmable logic array (PLA), which logic planes are normally programmable?

  • AAND plane only
  • BOR plane only
  • CBoth AND and OR planes
  • DNeither plane
Report an error
Correct Answer: C. Both AND and OR planes
Explanation: A PLA generally has programmable AND and programmable OR arrays, providing more flexible sum-of-products implementation than a PAL with a fixed OR structure.
Reference: Standard digital electronics: PLA architecture
Question 1292
Digital ElectronicsProgrammable Logic Devices

Compared with a PLA, a traditional PAL typically uses?

  • AProgrammable AND array and fixed OR array
  • BFixed AND array and programmable OR array
  • CProgrammable RAM cells only
  • DNo AND-OR structure
Report an error
Correct Answer: A. Programmable AND array and fixed OR array
Explanation: A conventional PAL has a programmable AND plane feeding a fixed OR plane, while a PLA normally allows both planes to be programmed.
Reference: Standard digital electronics: PAL architecture
Question 1293
Digital ElectronicsLogic Families

In ideal CMOS logic under steady DC conditions, the input current is approximately?

  • AVery large
  • BApproximately zero except leakage
  • CEqual to output current
  • DFixed at 1 mA
Report an error
Correct Answer: B. Approximately zero except leakage
Explanation: The insulated MOS gate draws essentially no DC input current ideally; practical devices have small leakage and transient charging current.
Reference: Standard digital electronics: CMOS input characteristics
Question 1295
Digital ElectronicsSequential Timing

A synchronous finite-state machine has a maximum combinational-path delay of 18 ns and flip-flop setup time of 2 ns. Ignoring clock skew and clock-to-Q delay, the clock period must be at least?

  • A9 ns
  • B16 ns
  • C18 ns
  • D20 ns
Report an error
Correct Answer: D. 20 ns
Explanation: The receiving flip-flop needs stable data before the clock edge, so Tclk ≥ 18 ns + 2 ns = 20 ns under the stated assumptions.
Reference: Standard digital electronics: synchronous timing
Question 1297
Digital ElectronicsFinite State Machines

Which statement correctly distinguishes a Moore machine from a Mealy machine?

  • AMoore output depends only on present state, while Mealy output can depend on present state and input
  • BMoore has no states
  • CMealy output depends only on the clock frequency
  • DMoore cannot be implemented with flip-flops
Report an error
Correct Answer: A. Moore output depends only on present state, while Mealy output can depend on present state and input
Explanation: In a Moore FSM, outputs are functions of state only. In a Mealy FSM, outputs are functions of both present state and current inputs.
Reference: Standard digital electronics: Moore and Mealy machines
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