Question 1

Serial vs. parallel: conductor count Between serial and parallel data formats, which requires fewer conductors to transfer data?

Accepted Answer

Introduction / Context: Cabling complexity and pin count are major considerations in system cost, size, and reliability. Serial links minimize the number of required conductors and have become the dominant approach in modern high-speed interconnects like USB, PCIe, and SATA. Given Data / Assumptions: We compare generic serial and parallel formats. A single serial data path per direction is considered, acknowledging a return or reference. Parallel requires multiple data lines for multi-bit width, plus control lines. Concept / Approach: Serial transmission sends bits sequentially on one data line per direction. Parallel transmission sends multiple bits simultaneously, each requiring a dedicated conductor, which multiplies pin count and cable bulk. Step-by-Step Reasoning: Identify conductor usage in serial: one data path per direction, minimal lines.Identify conductor usage in parallel: one line per bit plus control lines.Conclude that serial requires fewer conductors. Verification / Alternative check: Compare a traditional 8-bit parallel bus to a UART link: 8 data lines vs one TX and one RX (plus ground). The serial solution clearly uses fewer conductors for equivalent data movement over time. Why Other Options Are Wrong: Parallel: by definition uses more conductors. Both the same or cannot tell: not accurate in general practice. Depends only on voltage levels: conductor count is not determined by voltage levels. Common Pitfalls: Ignoring differential signaling pairs. Even then, serial still uses far fewer pairs than parallel buses of the same width. Equating bandwidth with conductor count; serial compensates with higher line rates. Final Answer: Serial

Question 2

Tradeoffs of serial data transfer What is one relative disadvantage of serial transfer compared with a same-generation parallel interface?

Accepted Answer

Introduction / Context: Historically, for a given technology generation, serial links transferred one bit at a time and were therefore slower than equally clocked parallel buses that moved many bits simultaneously. Although modern serial links achieve high throughput via very high signaling rates and encoding, the classical disadvantage in basic coursework is lower raw bit transfer per clock versus a wide parallel bus. Given Data / Assumptions: Comparing same-era, similarly clocked serial and parallel systems. Ignoring advanced techniques like multi-lane bonding or very high serial baud rates. Focusing on simple conceptual differences taught in introductory courses. Concept / Approach: A parallel bus with N data lines can, in principle, move N bits per clock, while a single serial line moves 1 bit per clock. Thus, at the same clock frequency and absent other constraints, the parallel bus is faster in raw throughput, making basic serial transfer relatively slower. Step-by-Step Reasoning: Assume both buses operate at the same clock rate.Parallel sends N bits per cycle; serial sends 1 bit per cycle.Therefore, serial appears slower when viewed per clock. Verification / Alternative check: Consider an 8-bit parallel port at 1 MHz versus a 1-bit serial line at 1 MHz. The parallel port can deliver 8 Mbit/s, while the serial line delivers 1 Mbit/s, confirming the basic teaching example. Why Other Options Are Wrong: Too many conductors: this describes parallel, not serial. Interconnect complexity: serial usually simplifies cabling and connectors. Only very short distances: serial is actually preferred for longer distances, especially differential serial. Cannot be error checked: serial protocols commonly use parity, CRC, or checksums. Common Pitfalls: Assuming modern serial is always slower. High-speed serial can far exceed old parallel buses due to high baud rates and efficient encoding. Confusing logical serial with physical wiring needs like ground or differential pairs. Final Answer: It is slow.

Question 3

Inverter logic behavior For a NOT gate (inverter) operating with standard positive logic, under what input condition is the output HIGH?

Accepted Answer

Introduction / Context: An inverter, or NOT gate, is the simplest logic element that performs logical negation. Mastering its truth table is essential, as inverters appear in virtually every digital design, from simple combinational networks to complex synchronous systems. Given Data / Assumptions: Standard positive logic: HIGH means logical 1, LOW means logical 0. Ideal logic levels and no undefined states considered. Single-input device; there are not multiple inputs on a NOT gate. Concept / Approach: The inverter outputs the logical complement of its input. This is captured by the Boolean expression Y = NOT(A). Therefore, when the input is LOW (0), the output must be HIGH (1), and when the input is HIGH (1), the output must be LOW (0). Step-by-Step Solution: Write the relationship: Y = NOT(A).Case A = 0 → Y = 1 (output HIGH).Case A = 1 → Y = 0 (output LOW). Verification / Alternative check: Truth tables in any digital logic reference confirm that the only time the NOT gate outputs HIGH is when the input is LOW. Gate-level simulations likewise show perfect inversion in the absence of timing hazards. Why Other Options Are Wrong: Input HIGH yields output LOW, not HIGH. Input transitions do not inherently force a specific steady-state output; the logic level at the moment determines the output. Removing supply voltage disables the gate, not a valid logic operation. Both inputs LOW does not apply; a NOT gate has only one input. Common Pitfalls: Confusing NOT with buffer. A buffer outputs the same level; a NOT inverts it. Mixing active-low conventions. In active-low signal naming, bubbles indicate inversion; always check schematics carefully. Final Answer: the input is LOW

Question 4

Signals and systems — frequency from period A periodic pulse has a measured period of 15 ms. Calculate the signal's frequency in hertz (Hz), using f = 1 / T, and choose the closest value.

Accepted Answer

Introduction / Context: In basic signals and systems, frequency and period describe the same repetitive behavior from two viewpoints. Frequency (in hertz) tells how many cycles occur each second, while period (in seconds) tells how long a single cycle lasts. Converting between them is a core skill used in electronics, communications, and instrumentation. Given Data / Assumptions: Period T = 15 ms. We want frequency f in hertz (Hz). Use ideal relationship f = 1 / T with consistent SI units. Concept / Approach: The fundamental relationship for periodic signals is f = 1 / T. To apply it correctly, convert milliseconds to seconds because hertz uses per-second units. 1 ms = 10^-3 s, so 15 ms = 15 * 10^-3 s = 0.015 s. Step-by-Step Solution: Convert 15 ms to seconds: T = 0.015 s.Apply the formula: f = 1 / T.Compute: f = 1 / 0.015 = 66.666... Hz.Round to the closest listed option: 66.66 Hz. Verification / Alternative check: If T decreases, f increases proportionally. A 10 ms period corresponds to 100 Hz; since 15 ms is 1.5 times longer than 10 ms, the frequency should be 100 / 1.5 ≈ 66.7 Hz, confirming the result. Why Other Options Are Wrong: 6.66 Hz: Off by a factor of 10 (used T in seconds but mistakenly scaled). 666.66 Hz: Off by a factor of 10 (likely used milliseconds without unit conversion). 15 Hz: Incorrectly treated period value as frequency directly. Common Pitfalls: Forgetting to convert milliseconds to seconds, mixing up period and frequency, or inverting the wrong value. Always check units before calculating. Final Answer: 66.66 Hz

Question 5

Digital vs. analog representations Which statement best describes digital representations of numerical quantities in instrumentation and computing systems?

Accepted Answer

Introduction / Context: Digital systems encode information using discrete states (often 0 and 1) rather than continuously variable signals. Understanding the difference between discrete-step digital representations and continuous analog representations is foundational for studying data converters, logic design, and digital signal processing. Given Data / Assumptions: The question contrasts how digital values behave compared to analog values. We assume ideal digital levels (noise margins, quantization) and typical binary encoding. Concept / Approach: Digital quantities change in discrete increments (quantization levels). The numeric value is represented by a finite set of code words (e.g., binary numbers). As the underlying physical quantity changes, the digital code updates stepwise, not continuously. This property enables robust storage, computation, and transmission with error detection/correction. Step-by-Step Solution: Identify what “digital” implies: finite set of allowed states or codes.Relate numeric magnitude to code: larger quantities map to larger numeric codes.Conclude that digital quantities vary in discrete steps as the real-world value changes. Verification / Alternative check: A digital voltmeter with 12-bit ADC shows counts from 0 to 4095. As input increases, the display steps through integer codes; the change is not continuous but quantized, confirming the stepwise nature. Why Other Options Are Wrong: Continuously changing / continuous range: describes analog, not digital. Constant and direct proportion without steps: ignores quantization; more analog-like. “Difficult to interpret” is subjective and not a defining property of digital data. Common Pitfalls: Confusing sampling (time discretization) with quantization (amplitude discretization). Digital systems may sample continuously changing analog signals but still represent them in discrete amplitude steps. Final Answer: that vary in discrete steps in proportion to the values they represent.

Question 6

Data transfer methods in digital systems Which transmission format can deliver several bits of information faster under the same clock conditions?

Accepted Answer

Introduction / Context: Digital systems move data either serially (one bit at a time) or in parallel (multiple bits simultaneously on multiple lines). Selecting a method involves trade-offs among speed, pin count, cable complexity, and signal integrity. Given Data / Assumptions: Equal clock rate and comparable signaling quality. Parallel buses have one wire per bit; serial links have one (or few) differential pairs. Concept / Approach: Under the same clock, a k-bit-wide parallel bus can transfer k bits per clock, whereas a single-lane serial link transfers 1 bit per clock (without serialization techniques like higher line rate, encoding, or multiple lanes). Thus, raw throughput favors parallel when width is available. Step-by-Step Solution: Assume n data lines in parallel → n bits per clock period.Assume serial single-lane → 1 bit per clock period.Therefore, parallel delivers more bits per unit time given equal clock frequency. Verification / Alternative check: Classic microprocessor buses (8-bit, 16-bit, 32-bit) illustrate higher data per cycle than traditional UART serial links at the same fundamental clock. Modern high-speed serial compensates with much higher line rates, but the question holds “under the same clock conditions.” Why Other Options Are Wrong: Serial: Not faster per clock for multiple bits unless line rate is proportionally higher. Both are the same / Cannot tell: With the given condition (same clock), parallel is predictably higher throughput. Common Pitfalls: Confusing practical implementations (PCIe high-speed serial) with the conceptual throughput per clock. The principle here is width versus lane rate. Final Answer: Parallel

Question 7

Logic level conventions — positive logic In positive-logic systems, which mapping between voltage level and logic value is used?

Accepted Answer

Introduction / Context: Digital logic can be defined using polarity conventions. Positive logic is the most common convention in which higher voltage represents the logic TRUE state. Knowing this mapping is essential when reading datasheets, designing interfaces, or interpreting timing diagrams. Given Data / Assumptions: Standard TTL/CMOS-like logic families. No inverted or negative-logic reinterpretations applied. Concept / Approach: In positive logic, a higher voltage (near Vcc) corresponds to logic 1 (TRUE), and a lower voltage (near ground) corresponds to logic 0 (FALSE). Negative logic uses the opposite mapping. The choice affects naming (active-high vs. active-low signals) but not the physical operation once interpreted consistently. Step-by-Step Solution: Identify convention: positive logic.Map levels: HIGH → 1, LOW → 0.Select the option that states this mapping explicitly. Verification / Alternative check: Look at common signals like RESET active-high versus RESET̅ (active-low). In positive logic, asserting a signal usually means driving it HIGH to indicate logic 1. Why Other Options Are Wrong: LOW = 1, HIGH = 0: Negative-logic mapping, not positive. Only HIGHs/Only LOWs: Illogical since both levels are required for binary logic. Common Pitfalls: Confusing electrical polarity with logical meaning. Always check whether a signal is active-high or active-low in schematics and code. Final Answer: a HIGH = 1, a LOW = 0

Question 8

Definition and role of an ADC in mixed-signal systems What does an analog-to-digital converter (ADC) do?

Accepted Answer

Introduction / Context: An analog-to-digital converter (ADC) bridges the physical world of continuous signals (sound, temperature, voltage) and the digital domain of processors and logic. Mastering what an ADC does is the first step toward understanding sampling, quantization, and data acquisition systems. Given Data / Assumptions: Input is an analog signal (continuous amplitude, often voltage). Output is a digital code (binary representation). Ideal behavior assumed (no nonlinearity, noise, or jitter for the basic definition). Concept / Approach: An ADC samples the input at discrete time intervals and quantizes each sample into one of 2^N levels (for an N-bit converter). The result is a digital word suitable for storage, processing, or transmission. Core specs include resolution (bits), sampling rate, input bandwidth, and effective number of bits (ENOB). Step-by-Step Solution: Identify the function: convert analog to digital.Recognize that the ADC outputs binary codes proportional to input amplitude.Select the option explicitly stating this transformation. Verification / Alternative check: Consider a microphone signal digitized by an audio ADC; the digital samples can be processed or stored. Playing back requires the inverse device (DAC) to reconstruct analog waveforms for speakers. Why Other Options Are Wrong: “Makes digital signals” is vague and incomplete. “Allows the use of digital signals” is overly general, not a definition. “Stores information on a CD” describes storage media, not conversion. Common Pitfalls: Confusing ADC with DAC; overlooking that sampling and quantization introduce error (quantization noise), which is part of real-world ADC behavior. Final Answer: It takes analog signals and puts them in digital format.

Question 9

Place value in base-10 In the decimal (base-10) numbering system, which digit position is the most significant digit (MSD)?

Accepted Answer

Introduction / Context: Positional number systems assign weights to digits based on their position. In base-10, each place to the left is worth ten times the place to its right. The most significant digit (MSD) has the greatest weight and most influence on the numeric value. Given Data / Assumptions: Base-10 positional notation. MSD definition sought. No leading zeros unless explicitly stated. Concept / Approach: The MSD is the leftmost nonzero digit in the integer portion of a number. It contributes the largest magnitude because its positional weight (10^n) is the highest. Conversely, the least significant digit (LSD) is the rightmost digit, weight 10^0 in integers or the smallest fractional weight to the right of the decimal. Step-by-Step Solution: Identify place-value weights: …, 10^3, 10^2, 10^1, 10^0.MSD corresponds to the highest power of 10 present (leftmost nonzero digit).Therefore, MSD is “the digit with the most weight.” Verification / Alternative check: In 7,254 the MSD is 7 (in the thousands place). Changing the MSD changes the number by thousands, while changing the LSD changes it by ones only, reinforcing the weight concept. Why Other Options Are Wrong: Middle digit/right of decimal/last on the right: These refer to positions but not necessarily the most significant one. Common Pitfalls: Confusing MSD with “first typed digit” or misapplying to floating-point notation; always determine significance by position weight, not appearance order alone. Final Answer: The digit with the most weight

Question 10

AND gate behavior Under what input condition is the output of an AND gate LOW?

Accepted Answer

Introduction / Context: Logic gates implement Boolean operations. The AND gate outputs TRUE (logic 1) only when all its inputs are TRUE. Understanding its truth table is essential for designing combinational logic and control circuits. Given Data / Assumptions: Ideal AND gate with two or more inputs. Positive logic convention (HIGH = 1, LOW = 0). Concept / Approach: Boolean AND corresponds to multiplication in binary algebra: 1 * 1 = 1; any term being 0 forces the product to 0. Thus, a single LOW input guarantees a LOW output, regardless of other inputs. Step-by-Step Solution: Evaluate AND with inputs: if any input = 0 → output = 0.Only when all inputs = 1 does output = 1.Therefore, the output is LOW whenever any input is LOW. Verification / Alternative check: Construct the truth table for a two-input AND: (0,0)→0; (0,1)→0; (1,0)→0; (1,1)→1. This generalizes to more inputs: a single 0 yields 0 output. Why Other Options Are Wrong: All the time: An AND gate can output HIGH when all inputs are HIGH. When any input is HIGH: That describes OR-like behavior, not AND. When all inputs are HIGH: That is when the output is HIGH, not LOW. Common Pitfalls: Confusing AND with OR; misreading active-low logic symbols; forgetting positive vs. negative logic conventions. Final Answer: when any input is LOW

Question 11

Memory technologies — identify the semiconductor memory Which of the following choices is a semiconductor memory device used for random access storage?

Accepted Answer

Introduction / Context: Computer memory technologies range from semiconductor-based volatile storage to optical and magnetic nonvolatile media. Distinguishing these categories is important for system architecture, performance analysis, and embedded design. Given Data / Assumptions: Looking for a semiconductor memory type. Focus on mainstream components used as main memory or cache. Concept / Approach: Random Access Memory (RAM) is a semiconductor memory family (DRAM, SRAM). It provides read/write capability with fast access, typically volatile (contents lost at power-down). MAR (Memory Address Register) is a CPU register, not a memory technology. CD and CD-ROM are optical storage media, not semiconductor RAM. Step-by-Step Solution: Identify semiconductor memory candidates: RAM, ROM, Flash.Differentiate from registers and optical media: MAR is a register; CD/CD-ROM are optical discs.Select RAM as the correct semiconductor memory option provided. Verification / Alternative check: System block diagrams show RAM chips (DRAM DIMMs, SRAM caches) connected via memory buses; MAR appears within the CPU datapath; CDs attach via storage interfaces and have orders-of-magnitude different latency and bandwidth. Why Other Options Are Wrong: MAR: Not a memory device, a processor register. CD-ROM / CD: Optical media, non-semiconductor, sequential/sector access. Common Pitfalls: Confusing memory devices with architectural registers or with storage media. RAM is volatile, whereas optical discs are nonvolatile and much slower. Final Answer: RAM

Question 12

Duty cycle calculation from timing parameters A periodic digital waveform has pulse width tw = 6 ms and period T = 18 ms. Compute the duty cycle (%) = (tw / T) * 100.

Accepted Answer

Introduction / Context: Duty cycle quantifies the fraction of time a digital signal stays HIGH within one period. It is crucial for pulse-width modulation (PWM), timing analysis, power electronics, and clocking strategies where average power or effective value depends on on-time ratio. Given Data / Assumptions: Pulsed waveform with tw = 6 ms (HIGH time). Period T = 18 ms. Duty cycle D(%) = (tw / T) * 100. Concept / Approach: Use the definition directly, ensuring consistent units. Since both times are in milliseconds, unit conversion cancels out. Simplify the ratio and multiply by 100 to get a percentage. Step-by-Step Solution: Form ratio: tw / T = 6 / 18.Simplify: 6 / 18 = 1 / 3 ≈ 0.3333.Convert to percent: 0.3333 * 100 = 33.33…%.Rounded to listed choice: 33.3%. Verification / Alternative check: If the pulse is HIGH for 1/3 of the period and LOW for 2/3, average value of a 5 V signal would be about 1/3 * 5 ≈ 1.667 V, which is consistent with a 33.3% duty cycle interpretation in PWM systems. Why Other Options Are Wrong: 3.3%: Off by a factor of 10 (likely decimal-place error). 6% or 18%: Confuses pulse width or period with percent; incorrect ratio. Common Pitfalls: Mixing milliseconds with seconds unnecessarily, or flipping the ratio T / tw. Always confirm that duty cycle is on-time divided by period. Final Answer: 33.3%

Question 13

Binary fractions to decimal conversion Convert the fractional binary number 0001.0010₂ to its decimal (base-10) value.

Accepted Answer

Introduction / Context: Binary numbers can include fractional parts. Converting binary fixed-point values to decimal is essential for interpreting ADC outputs, fixed-point arithmetic in embedded systems, and digital signal processing where fractional precision matters. Given Data / Assumptions: Binary value: 0001.0010₂. Point location: four bits integer part, four bits fractional part. We need a base-10 decimal equivalent. Concept / Approach: Binary place values to the left of the point are powers of 2: …, 8, 4, 2, 1. To the right, they are fractional powers: 1/2, 1/4, 1/8, 1/16, etc. Sum the weighted contributions of bits that are 1. Leading zeros do not change the value. Step-by-Step Solution: Integer part 0001₂ = 1.Fractional part .0010₂ = (0 * 1/2) + (0 * 1/4) + (1 * 1/8) + (0 * 1/16) = 0.125.Total decimal value = 1 + 0.125 = 1.125. Verification / Alternative check: Multiply the fractional part by 10 is not valid in base-2; instead, verify by converting back: 1.125 decimal = 1 + 1/8 = 1.0010₂, which matches the given binary form. Why Other Options Are Wrong: 1.40 / 1.20 / 1.80: These decimals are not equal to 1 + 1/8. They imply different fractional sums like 0.4, 0.2, or 0.8, which do not correspond to .0010₂. Common Pitfalls: Misplacing fractional weights (confusing 1/2 with 1/8), or reading the binary fraction as if it were decimal digits. Always apply powers of two for each fractional bit position. Final Answer: 1.125

Question 14

Packaging in digital electronics In a plastic leaded chip carrier (PLCC) integrated-circuit package used on printed circuit boards, the J-shaped leads are arranged along how many sides of the package body?

Accepted Answer

Introduction / Context: Integrated-circuit (IC) packaging directly affects board layout, soldering process, and reliability. The plastic leaded chip carrier (PLCC) is a classic surface-mount package that uses J-leads. Knowing how many sides carry leads helps technicians choose footprints, plan routing, and understand socket compatibility. Given Data / Assumptions: Package type considered: PLCC (plastic leaded chip carrier). Lead style: J-lead bent under the package edges. Context: printed circuit board (PCB) assembly and footprint selection. Concept / Approach: PLCCs are square or nearly square bodies with leads on every edge. Each side carries an equal number of J-shaped leads that curl under the body. This is distinct from SOIC (two opposite rows) or SOT (one side for some variants). Thus, the lead distribution is four-sided. Step-by-Step Solution: Identify package: PLCC → J-leads under edges.Check geometry: square body → edges available on four sides.Manufacturing intent: distribute pins around entire periphery for compact routing.Conclusion: leads are present on all four sides. Verification / Alternative check: Compare with QFP and LQFP, which also have leads on four sides but use gull-wing leads. PLCC is similar in the “four-sides” aspect, differing only by lead form (J-lead vs gull-wing). Why Other Options Are Wrong: One side / two sides / three sides: These correspond to other package families (e.g., SOT/SOIC for two sides), not PLCC. Common Pitfalls: Confusing PLCC with SOIC or DIP; SOIC and DIP have leads on two sides only, while PLCC has leads on all four sides. Final Answer: four sides

Question 15

Digital transmission methods If a digital signal must travel over a single conductor plus a reference ground (two wires total), in which transmission mode must it be sent?

Accepted Answer

Introduction / Context: Signal wiring constraints often dictate whether data is sent in serial or parallel form. Understanding the physical link (number of conductors available) helps determine the feasible transmission mode for digital communication between devices. Given Data / Assumptions: Available conductors: one signal line plus a ground reference. Digital data stream to be delivered from a transmitter to a receiver. No additional clock or strobe lines are specified. Concept / Approach: Parallel transmission requires multiple simultaneous conductors (one per bit, plus control lines). With only one signal conductor and ground, all bits must be sent sequentially over time, which is the definition of serial transmission. Encoding, clock recovery, and line coding (e.g., NRZ, Manchester) make this practical. Step-by-Step Solution: Count conductors: only one signal line is present.Parallel data requires as many conductors as there are data bits → not possible here.Therefore, bits must be time-multiplexed over a single line → serial transmission. Verification / Alternative check: Common interfaces like UART (TX/RX, each a single line plus ground) and one-wire buses demonstrate serial transfer over minimal conductors. Why Other Options Are Wrong: Parallel: needs multiple lines; impossible with one signal conductor.Analog: the data is digital; analog is a different signaling category.Slow speed: speed is not inherently determined by the number of wires. Common Pitfalls: Assuming “single wire” implies low speed; modern serial links can be very fast with appropriate coding and termination. Final Answer: serial.

Question 16

Bistable storage element In digital electronics, a flip-flop is characterized by how many stable states under normal operating conditions?

Accepted Answer

Introduction / Context: Flip-flops are fundamental memory elements used to store one bit of information. Recognizing their stability characteristics helps in understanding registers, counters, and state machines. Given Data / Assumptions: A flip-flop is a sequential logic element with feedback. Normal operation excludes metastability events; we consider stable resting states. Concept / Approach: A flip-flop is inherently bistable: it has exactly two stable output states that it can hold indefinitely (logic 0 or logic 1) until a triggering event causes a change. This is unlike monostable or astable multivibrators, which have one or zero stable states respectively. Step-by-Step Solution: Identify device type: flip-flop → bistable multivibrator.Stable states: Q = 0 or Q = 1.Conclusion: exactly two stable states. Verification / Alternative check: Truth tables and characteristic equations (e.g., for D, JK, T flip-flops) show the device latches and maintains one of two states between clock events. Why Other Options Are Wrong: One / zero stable states: describe monostable or astable circuits, not flip-flops.“None of the above”: incorrect because the correct choice is explicitly listed. Common Pitfalls: Confusing flip-flops with latches; both are bistable, but differ by level- vs edge-sensitive control. Final Answer: two stable states

Question 17

Binary-to-decimal conversion practice Convert the 8-bit binary number 10000110₂ to its decimal (base-10) equivalent.

Accepted Answer

Introduction / Context: Converting between binary and decimal is a core skill in digital electronics and computer architecture. This question reinforces positional weighting of bits in an 8-bit unsigned number. Given Data / Assumptions: Binary input: 10000110₂. Unsigned interpretation (no sign bit behavior implied). Place values: 2^7 to 2^0 from left to right. Concept / Approach: Each binary 1 adds its positional weight to the total. For 8 bits, the weights are 128, 64, 32, 16, 8, 4, 2, 1. Sum only those weights where the bit is 1. Step-by-Step Solution: Write weights under bits: 1 0 0 0 0 1 1 0 → 128, 0, 0, 0, 0, 4, 2, 0.Add active weights: 128 + 4 + 2 = 134.Therefore, 10000110₂ = 134₁₀. Verification / Alternative check: Convert 134 back to binary: 128 + 4 + 2 → bits at 2^7, 2^2, 2^1 set → 10000110₂, confirming the result. Why Other Options Are Wrong: 144₁₀, 110₁₀, 126₁₀: each includes incorrect weighting or extra/missing powers of two. Common Pitfalls: Misreading bit positions (especially internal zeros) or forgetting that the leftmost bit is 2^7 in an 8-bit number. Final Answer: 13410

Question 18

Serial vs. parallel data lines Which statement best describes the wiring requirement for parallel transmission of digital data between a sender and a receiver?

Accepted Answer

Introduction / Context: Choosing between serial and parallel links affects cabling, connectors, cost, and speed. Understanding the line requirements prevents design mistakes in hardware interfacing. Given Data / Assumptions: Parallel interfaces send multiple bits simultaneously. Each bit typically needs its own dedicated conductor plus grounds and control lines. Concept / Approach: Parallel transfer uses N data lines for N-bit words so all bits arrive concurrently. This increases connector size and crosstalk risk but reduces per-word latency over short distances. Step-by-Step Solution: Define parallel: multiple bits in the same time slot.Consequence: provide one conductor per bit path.Therefore, the number of signal lines equals the number of bits transmitted in parallel. Verification / Alternative check: Legacy printer ports (8-bit parallel) used eight data lines plus control/status lines, illustrating the rule. Why Other Options Are Wrong: “Much slower”: parallel is not inherently slower; it can be faster over short cables.“Only one signal line”: describes serial, not parallel.“Less expensive”: usually false due to more conductors and larger connectors. Common Pitfalls: Ignoring skew and crosstalk; at high speed and distance, serial links often outperform parallel. Final Answer: requires as many signal lines between sender and receiver as there are data bits.

Question 19

Coding fundamentals in digital systems An encoder in digital electronics performs which basic conversion?

Accepted Answer

Introduction / Context: Encoders and decoders are complementary building blocks used in keyboards, communication, and multiplexing systems. Knowing their direction of conversion is key for correct application. Given Data / Assumptions: “Noncoded” refers to many individual lines or states (e.g., one-hot lines). “Coded” refers to a compact binary representation. Concept / Approach: An encoder compresses multiple input lines (often one-hot) into a smaller set of binary outputs. Conversely, a decoder expands binary inputs into multiple output lines. Level inversion (HIGH to LOW) is unrelated to encoding. Step-by-Step Solution: Identify device: encoder.Function: map many inputs to fewer binary outputs.Result: noncoded → coded. Verification / Alternative check: Example: a 10-to-4 keypad encoder maps ten keys to a 4-bit code. Why Other Options Are Wrong: “Coded to noncoded”: that is a decoder's job.“HIGHs to LOWs” / “LOWs to HIGHs”: describe inversion or logic-level translation, not encoding. Common Pitfalls: Confusing priority encoders (which also resolve multiple simultaneous inputs) with decoders. Final Answer: noncoded information into coded form

Question 20

Exponents refresher for digital math For any nonzero number x, what is the value of x raised to the zero power (x^0)?

Accepted Answer

Introduction / Context: Exponential rules frequently appear in digital systems (e.g., 2^n states, memory sizes). A basic but crucial identity is the zero-exponent rule for nonzero bases. Given Data / Assumptions: Base x is nonzero. Expression: x^0. Concept / Approach: Exponent laws: x^a / x^a = x^(a−a) = x^0. Because any nonzero number divided by itself equals 1, x^0 must be 1 for consistency across algebraic operations. Step-by-Step Solution: Start with x^n / x^n = 1 (x ≠ 0).Apply exponent subtraction: x^(n−n) = x^0.Therefore, x^0 = 1. Verification / Alternative check: Consider sequence x^3, x^2, x^1, x^0 as successive division by x; dividing x by x yields 1. Why Other Options Are Wrong: Zero: would contradict exponent laws unless x = 0, and 0^0 is indeterminate.“That number”: implies x^0 = x, which is false for x ≠ 1.Ten: unrelated to the base or exponent rule. Common Pitfalls: Confusing the special, undefined case 0^0 with the general identity for nonzero x. Final Answer: one

Digital Concepts Questions