Question 1

In computer hardware, the effective speed and performance of a microprocessor primarily depend on which combination of factors?

Accepted Answer

Introduction / Context: Microprocessor performance is often advertised using clock frequency values in megahertz or gigahertz. However, real world speed depends on many architectural details such as pipelining, cache size, bus widths, and how efficiently instructions are executed. This question tests your understanding that processor speed is multi dimensional and cannot be judged by a single specification parameter. Given Data / Assumptions: Clock frequency is one factor affecting performance. Word length or data bus width is another potential factor. Microarchitecture features such as cache, pipelines, and instruction set design also affect speed. Brand name alone does not guarantee performance. Concept / Approach: The time taken by a processor to complete a task depends on how many instructions are executed and how many clock cycles each instruction needs. Architectural features such as deep pipelines, superscalar execution, and branch prediction can reduce cycles per instruction. Large and fast caches reduce the time spent waiting for memory. A wider bus or higher memory bandwidth can deliver data faster. Therefore, performance is a result of the combination of clock speed and design features, not clock speed alone. Step-by-Step Solution: Step 1: Consider option A. Clock speed certainly influences how many cycles per second the CPU can generate, but by itself it does not describe how many useful instructions are completed per cycle.Step 2: Consider option B. Word length affects how large numbers can be represented but does not by itself guarantee higher performance for all tasks.Step 3: Remember that modern processors use techniques such as pipelining, super scalar execution, out of order execution, and multiple cache levels to speed up real workloads.Step 4: Recognize that option C explicitly includes clock speed and these architectural factors together, which matches how performance is usually analyzed. Verification / Alternative check: Compare two real processors: one might run at a slightly lower clock speed but have more efficient cores, better cache architecture, and more instructions per cycle. In benchmarks, this processor can outperform another with a higher clock rate but an older architecture. This practical observation supports the idea that performance is the result of clock speed plus design efficiency. Word length is also relevant, but only as part of the overall design considerations. Why Other Options Are Wrong: Option A: Ignores architectural improvements. Two processors with the same clock speed can have very different performance levels.Option B: Focuses only on data bus width or word length, which mainly affects addressable memory and numeric range, not general performance alone.Option D: Brand name is a marketing label and does not directly determine speed. Different models from the same brand can have widely varying performance. Common Pitfalls: Many beginners assume that a higher gigahertz value automatically means a faster processor. This was already misleading when comparing different generations of the same architecture and is even worse when comparing across architectures. Another common mistake is to equate bit width with speed instead of capacity. Performance evaluation should consider cycles per instruction, instructions per cycle, memory hierarchy, and workload characteristics. Final Answer: The correct answer is On a combination of clock speed, internal architecture, cache and bus design, and instruction set efficiency.

Question 2

Under common PC operating systems, what is the maximum number of logical drives that can be configured on a single physical hard disk?

Accepted Answer

Introduction / Context: In personal computer systems, a physical hard disk can be divided into partitions, which the operating system may present as logical drives with drive letters such as C, D, or E. Legacy systems such as DOS and early versions of Windows imposed specific limits on how many logical drives could exist. This question checks your awareness of traditional constraints linked to drive letters and logical drive configuration. Given Data / Assumptions: We are considering typical PC environments that use drive letters, such as DOS and early Windows. A logical drive is a partition that is assigned a drive letter. Drive letters usually range from A onward in the English alphabet. Concept / Approach: Historically, drive letters A and B were reserved for floppy drives, and letters C through Z could be assigned to hard disk partitions, optical drives, and other logical drives. That gives a theoretical maximum of 24 possible drive letters. A single physical disk can host multiple partitions and logical drives, but the number is constrained by the available drive letters and partitioning rules. Standard multiple choice questions often reference 24 as the maximum number of logical drives possible on one disk under these conventional limits. Step-by-Step Solution: Step 1: Count the potential drive letters from C to Z, which yields 24 letters.Step 2: Recognize that these letters represent the maximum number of logical drives that can be mounted in the system.Step 3: Understand that in theory a single physical disk could consume all of these letters if partitioned appropriately.Step 4: Match this knowledge to the option that states a maximum of 24 logical drives. Verification / Alternative check: Although modern operating systems support more flexible volume management, exam questions based on traditional PC partitioning usually refer to the classic drive letter model. Under that model, there is a finite set of drive letters and thus a limited number of logical drives. Practical installers and disk management tools will not allow more logical drives than there are letters to assign, reinforcing the 24 drive limit from C onwards. Why Other Options Are Wrong: Option A: Four logical drives corresponds roughly to four primary partitions, not the total number of logical drives possible when using extended partitions.Option B: Eight is too low and does not align with the traditional drive letter limit.Option D: Infinite logical drives are impossible because the operating system and file system impose structural limits, including drive letters and partition table formats. Common Pitfalls: Students sometimes confuse the maximum number of primary partitions with the maximum number of logical drives. Traditional MBR partitioning allows up to four primary partitions, but within an extended partition you can create multiple logical drives, up to the drive letter limit. Another confusion comes from modern systems that use GUID Partition Table and mount points instead of drive letters, but exam questions usually stick to the simpler legacy model. Final Answer: The correct answer is A maximum of 24 logical drives on a single physical disk under common PC operating systems.

Question 3

In a pipelined processor, what are the main types of hazards that can occur, and how are they typically avoided?

Accepted Answer

Introduction / Context: Pipelining is a key technique used in modern processors to increase instruction throughput by overlapping different stages of execution. However, pipelining introduces hazards that can prevent the next instruction from executing in the next cycle. Understanding the types of hazards and the strategies used to handle them is fundamental in computer architecture. Given Data / Assumptions: We assume a basic pipelined processor with stages such as fetch, decode, execute, memory, and write back. The question asks for the different types of hazards in such a system. We also consider common methods used to avoid or reduce the impact of these hazards. Concept / Approach: There are three primary categories of pipeline hazards. Structural hazards occur when hardware resources are insufficient to support all concurrent operations. Data hazards arise when instructions depend on the results of previous instructions that have not yet completed within the pipeline. Control hazards (or branch hazards) occur due to changes in the flow of control, primarily from branch instructions. Designers use techniques such as pipeline stalls, operand forwarding, out of order execution, branch prediction, and speculative execution to reduce the performance penalties caused by these hazards. Step-by-Step Solution: Step 1: Recall the three categories of pipeline hazards: structural, data, and control hazards.Step 2: For structural hazards, remember that they arise when two stages need the same hardware resource in the same cycle, such as a single memory unit for both instruction fetch and data access.Step 3: For data hazards, think about instructions that read a register soon after another instruction writes to it. Without special handling, the later instruction may see the old value.Step 4: For control hazards, consider what happens when a branch changes the instruction flow and the pipeline has already fetched incorrect instructions.Step 5: Match these ideas to the option that correctly lists structural, data, and control hazards and mentions realistic avoidance strategies. Verification / Alternative check: Standard computer architecture textbooks describe exactly these three hazard types and present hardware and software techniques to mitigate them. For example, operand forwarding and hazard detection units help with data hazards, while branch prediction reduces control hazards. Additional functional units or separate instruction and data memories can reduce structural hazards. The presence of all three in the same option confirms that it is the correct choice. Why Other Options Are Wrong: Option B: Uses terms from programming language theory and runtime errors, not the hardware hazards of pipeline execution.Option C: Incorrectly claims that only structural hazards exist and denies the well known data and control hazards.Option D: Talks about electrical hazards such as electric shock, which are safety issues, not pipeline hazards. Common Pitfalls: Students sometimes confuse data hazards with logical programming bugs, but data hazards occur even when the program is correct because of overlapping execution stages. Another mistake is to think that a good compiler can completely eliminate hazards. While compilers can reorder and schedule instructions to reduce hazards, hardware mechanisms are still needed. Understanding the classification helps when analyzing pipeline timing diagrams and performance. Final Answer: The correct answer is Structural, data, and control hazards that are handled using techniques like forwarding, stalling, and branch prediction.

Question 4

Which statement best describes the operation of a transmission gate–based level sensitive D latch in digital circuit design?

Accepted Answer

Introduction / Context: D latches are basic storage elements used in digital circuits to hold a single bit of data. A transmission gate based D latch implements this function using CMOS transmission gates as controlled bidirectional switches. Understanding how a level sensitive D latch works is important for learning how flip flops and registers are built in hardware. Given Data / Assumptions: The device is a D latch, not a full edge triggered flip flop. The latch is implemented using transmission gates controlled by an enable or clock signal. We assume the latch is level sensitive, not edge triggered. Concept / Approach: A level sensitive D latch passes input D to output Q whenever the enable signal is at the active level, often logic high. During this transparent phase, changes at D appear at Q. When the enable signal goes to the inactive level, the latch stops passing the input and holds or latches the last value that was present at the moment the gate turned off. Transmission gates act as electronic switches controlled by complementary signals, allowing or blocking data flow while maintaining low resistance and good voltage levels. The description that matches this behavior is the correct one. Step-by-Step Solution: Step 1: Recall that transmission gate latches are level sensitive. When the enable is high, the latch is transparent.Step 2: When the enable goes low, the path from D to Q is turned off, and internal feedback maintains the stored value.Step 3: Note that this is different from an edge triggered flip flop, which samples only at clock edges.Step 4: Match this operation to the option that explicitly mentions transparent behavior when enable is active and latching when enable becomes inactive. Verification / Alternative check: In circuit diagrams, a transmission gate based D latch often shows a pair of CMOS transmission gates driven by complementary enable and inverted enable signals. Simulation or timing diagrams confirm that while the enable is high, output Q tracks input D with some delay, and when the enable goes low, Q holds its last value. There is no edge triggered behavior because the latch responds to the level of the control signal, not just a transition. Why Other Options Are Wrong: Option B: Describes an edge triggered flip flop, not a level sensitive latch, and therefore does not match the specified circuit.Option C: Suggests analog storage only, but digital latches are designed to hold distinct logic 0 and logic 1 values even though the underlying physics is analog.Option D: Claims the latch works without any enable or clock, which contradicts the definition of a controlled storage element. Common Pitfalls: A frequent confusion is between latches and flip flops. Latches are level sensitive, while flip flops are edge triggered. Another pitfall is ignoring the role of feedback in holding the stored value when the transmission gate is off. Understanding these differences helps when analyzing timing issues such as transparency windows and potential race conditions in sequential logic. Final Answer: The correct answer is It transparently passes the D input to Q while the enable signal is high and latches the last value when the enable goes low, using CMOS transmission gates as bidirectional switches.

Question 5

In microprocessor terminology, why is the Intel 8085 commonly referred to as an 8 bit processor?

Accepted Answer

Introduction / Context: Microprocessors are often classified by the width of data they can process in a single operation. Terms such as 8 bit, 16 bit, and 32 bit processors are common in computer architecture. The Intel 8085 is widely described as an 8 bit microprocessor. This question asks why that classification is used and which internal feature of the processor it is based on. Given Data / Assumptions: The processor in question is the Intel 8085. We need to identify what defines it as an 8 bit device. Possible explanations involve memory size, pin count, instruction set size, or data path width. Concept / Approach: The bit width label of a processor usually refers to the width of the arithmetic logic unit and the internal data bus. An 8 bit processor can process 8 bits of data in a single operation, such as addition or logical operations. The 8085 has 8 bit general purpose registers and an 8 bit ALU. It can address more than 8 kilobytes of memory and has many more than eight instructions, so those factors do not determine the bit width classification. Step-by-Step Solution: Step 1: Recall that the 8085 microprocessor has 8 bit wide registers like the accumulator and general purpose registers.Step 2: The arithmetic logic unit can add, subtract, and perform logical operations on 8 bit values at a time.Step 3: Remember that the address bus for 8085 is 16 bits, so it can address up to 64 kilobytes of memory, which is already greater than 8 kilobytes.Step 4: Match this information to the option that mentions the 8 bit data bus and ALU width. Verification / Alternative check: Technical documentation for the 8085 describes it as an 8 bit microprocessor with a 16 bit address bus. The instruction set includes many opcodes, far more than eight. The package has forty pins, not eight. All of these details confirm that the 8 bit label is based on the width of the data path and ALU, not memory size or pin count. Why Other Options Are Wrong: Option B: The 8085 can address up to 64 kilobytes, not only 8 kilobytes, so this statement is incorrect.Option C: The physical chip uses forty pins, so saying that it uses only eight pins is not accurate.Option D: The processor supports many different instructions, not just eight, so instruction count does not define its bit width. Common Pitfalls: Students sometimes mix up address bus width and data bus width. Address width determines how much memory can be directly addressed, while data width shows how many bits can be processed in one operation. Another confusion is assuming that bit width is related to the number of pins or the number of instructions, which are design details but not the main classification criterion. Final Answer: The correct answer is Because it has an 8 bit internal data bus and an arithmetic logic unit that processes 8 bits at a time.

Question 6

In cache coherence protocols, what does the acronym MESI stand for, and what does it describe?

Accepted Answer

Introduction / Context: In multiprocessor and multi core systems, each core may have its own cache. Cache coherence protocols are needed to keep cached copies of data consistent across cores. MESI is one of the most widely known cache coherence protocols. This question tests whether you remember what the MESI acronym stands for and its role in system design. Given Data / Assumptions: The acronym in question is MESI. We are dealing with multiprocessor or multi core cache coherence. The options include several expansions that may sound technical but only one is correct. Concept / Approach: MESI is a cache coherence protocol that defines four states for each cache line: Modified, Exclusive, Shared, and Invalid. These states describe whether a cached copy is clean or dirty, whether it is unique to one cache, shared among multiple caches, or invalid. By coordinating state transitions based on memory accesses and bus transactions, the protocol ensures that processors see consistent data even when they access shared memory concurrently. Step-by-Step Solution: Step 1: Recall the full form of MESI as Modified, Exclusive, Shared, Invalid.Step 2: Remember that each cache line in a MESI based system is tagged with one of these states.Step 3: Recognize that the purpose is to implement cache coherence in systems with more than one processor or core.Step 4: Match this understanding to the option that names these four states and refers to a cache coherence protocol. Verification / Alternative check: In many computer architecture references, MESI is described as the basic four state coherence protocol. Some variants extend it to more states, but the core idea remains a set of per line states. When a processor writes to a line, it may move to Modified state. When a line is present in only one cache and clean, it can be Exclusive. Shared indicates that multiple caches hold a clean copy. Invalid means the cache line cannot be used until refilled. This standard description confirms that option A is correct. Why Other Options Are Wrong: Option B: Memory Execution and Scheduling Interface is not a standard term in cache coherence and does not match the four state names.Option C: Multiple Enabled Serial Interrupts sounds like an interrupt related term and has nothing to do with cache line states.Option D: Maximum Execution Speed Indicator suggests a performance metric, which is unrelated to coherence protocols. Common Pitfalls: It is easy to confuse MESI with other acronyms in computer architecture if you only remember that it is four letters. Another pitfall is to recall only some of the states and forget the exact names. Remember that these protocols are usually documented with explicit state names and transition diagrams. Knowing them helps when analyzing memory consistency and performance in multi core systems. Final Answer: The correct answer is Modified, Exclusive, Shared, Invalid, describing cache coherence states for cache lines.

Question 7

Which of the following is a classic example of a one address, accumulator based microprocessor architecture?

Accepted Answer

Introduction / Context: Instruction set architectures can be classified by how many explicit addresses appear in each instruction. One address architectures are often accumulator based, where most operations implicitly use the accumulator register and specify only one explicit operand. This question asks you to identify a microprocessor that is a classic example of such a one address, accumulator based design. Given Data / Assumptions: We are comparing different Intel processors and coprocessors. We focus on instruction format and whether it is accumulator based with one explicit address. The question expects knowledge of the programming style and architecture of the 8085 and other devices. Concept / Approach: In a one address instruction set, many instructions have an implicit accumulator operand. For example, an instruction may operate on the accumulator and a memory or register operand specified in the instruction. The 8085 microprocessor is a well known 8 bit processor that uses the accumulator heavily. Instructions such as ADD M or ADD B implicitly add to the accumulator. Other architectures, like modern 32 bit processors, provide more general register to register operations with multiple explicit operands. Step-by-Step Solution: Step 1: Recall that the 8085 instruction set uses the accumulator as an implicit operand in many arithmetic and logic instructions.Step 2: Recognize that this style is characteristic of one address accumulator based architectures.Step 3: Compare with the 8087 numeric coprocessor, which primarily uses a stack based register file for floating point operations.Step 4: Compare with the 80386 and Pentium class processors, which use more general register addressing with multiple explicit operands.Step 5: Conclude that the 8085 is the classic example requested. Verification / Alternative check: Look at sample assembly code. On the 8085, instructions such as ADD B mean accumulator equals accumulator plus register B. The accumulator is not mentioned explicitly in the instruction format, which is typical of a one address design. In contrast, in 80386 assembly, you might write ADD EAX, EBX with both operands explicitly shown. This difference supports classifying the 8085 as the example of a one address, accumulator based architecture. Why Other Options Are Wrong: Option B: The 8087 is a numeric coprocessor with a stack oriented register model and is not a classic one address accumulator based microprocessor.Option C: The 80386 is a complex 32 bit microprocessor with rich addressing modes and two operand instructions, not a simple one address architecture.Option D: The Pentium 4 is a much newer superscalar processor with multiple pipelines and general purpose registers, again not a one address accumulator based example. Common Pitfalls: Students sometimes confuse the concept of one address instructions with the number of physical address lines. One address refers to the instruction format, not the hardware address bus. Another mistake is assuming that all older processors are one address architectures. While many early microprocessors were accumulator based, others used different styles, so you should always look at the instruction set to be sure. Final Answer: The correct answer is Intel 8085 microprocessor, which is largely accumulator based and often uses one address instructions.

Question 8

Which type of processor architecture is most strongly associated with deep instruction pipelining and simple, regular instruction formats?

Accepted Answer

Introduction / Context: Processor architectures are often classified as RISC or CISC. Reduced Instruction Set Computer designs emphasize simple, uniform instructions that lend themselves well to pipelined execution. Complex Instruction Set Computer designs historically used more complicated instructions. This question asks which architecture type is most closely linked with deep pipelining and regular instruction formats. Given Data / Assumptions: Pipelining is a technique for overlapping instruction execution stages. RISC designs emphasize simple and regular instructions. CISC designs historically used more complex and variable length instructions. Concept / Approach: RISC architectures were developed with the idea that a small, simple instruction set can be executed very efficiently if each instruction takes a similar amount of time and uses a regular format. This regularity allows CPU designers to construct deep pipelines where each stage handles a predictable amount of work. While modern CISC processors internally decode complex instructions into simpler micro operations and also use pipelining, the classic association of pipelining and simple instruction formats remains strongest with RISC. Step-by-Step Solution: Step 1: Recall the main ideas behind RISC: fixed or few instruction formats, load store architecture, and emphasis on simple operations.Step 2: Recognize that these properties help designers build pipelines with consistent stage timing.Step 3: Consider CISC, where variable length and complex instructions historically made naive pipelining more challenging.Step 4: Match this understanding to the option that clearly links RISC with pipelining and simple instructions. Verification / Alternative check: Looking at examples such as MIPS, ARM, or SPARC, which are classic RISC architectures, you see fixed length instructions and clean pipeline designs documented in textbooks. By contrast, x86, which is CISC, uses internal decoding into micro operations to support pipelining. While modern practice blurs the lines, exam questions usually focus on the original conceptual contrast, where RISC is the architecture type most associated with deep pipelining. Why Other Options Are Wrong: Option A: Incorrectly states that CISC always avoids pipelining. Modern CISC processors are heavily pipelined, but they are not the architecture most strongly associated with simple, regular instructions.Option C: SISD (single instruction single data) refers to a classification of parallelism, not specifically to pipelining or instruction format.Option D: Analog signal processors are not based on digital instruction sets and are not described using RISC or CISC terminology in the same way. Common Pitfalls: Students sometimes think that only RISC processors can be pipelined. In reality, almost all modern high performance processors, including those with CISC instruction sets, use pipelining. The key distinction is that RISC designs were intentionally simplified to make pipelining more straightforward. Another pitfall is confusing instruction set complexity with implementation complexity; even a simple instruction set can have a complex microarchitecture. Final Answer: The correct answer is RISC architecture, which is heavily designed around pipelining with simple, uniform instructions.

Question 9

In microprocessor history, how do first, second, third, and fourth generation microprocessors differ from one another?

Accepted Answer

Introduction / Context: The evolution of microprocessors can be grouped into generations based on technology, word size, and integration level. Early microprocessors started with small bit widths and simpler manufacturing processes. Later generations moved to larger bit widths, faster technologies, and higher levels of integration. This question asks you to identify a description that reasonably summarizes how four generations differ. Given Data / Assumptions: First generation microprocessors generally used PMOS technology and small bit widths such as 4 bits. Second generation devices adopted NMOS technology and 8 bit data paths. Third generation processors moved to 16 bit word lengths and improved HMOS processes. Fourth generation devices adopted 32 bit and higher word lengths with very large scale integration. Concept / Approach: Microprocessor generations are often described using both technology and word size. First generation PMOS designs such as Intel 4004 and 4040 used 4 bit data paths. Second generation NMOS devices such as the 8080 and 8085 used 8 bit paths. Third generation HMOS based devices such as the 8086 and 68000 families extended this to 16 bit. Later, fourth generation designs like the 80386 and beyond used 32 bit and higher widths with more sophisticated VLSI technologies. The option that captures this progression is the correct one. Step-by-Step Solution: Step 1: Identify that first generation devices used PMOS and very small word sizes, typically 4 bits.Step 2: Recognize that second generation devices shifted to NMOS and commonly used 8 bit data paths.Step 3: Recall that third generation devices employed HMOS or similar improved technologies and moved to 16 bit architectures.Step 4: Note that fourth generation devices advanced to 32 bit and then higher bit widths, leveraging VLSI processes.Step 5: Match these points to the option that lists 4 bit PMOS, 8 bit NMOS, 16 bit HMOS, and 32 bit VLSI. Verification / Alternative check: Consider concrete examples. The Intel 4004 is a 4 bit PMOS processor and is considered an early first generation microprocessor. The 8080 and 8085 are 8 bit NMOS processors representing the second generation. The 8086 and 68000 families are 16 bit HMOS or similar, representing third generation. The 80386 is a 32 bit processor built using more advanced VLSI, fitting the fourth generation description. This pattern agrees with option A. Why Other Options Are Wrong: Option B: Reverses the order of bit widths, which is the opposite of historical progress and does not reflect reality.Option C: Claims that chip size doubled while bit width stayed constant, which ignores the well known increase in word size and integration.Option D: Suggests generations are defined only by package color, which is clearly not a technical criterion. Common Pitfalls: Students may focus only on word size and forget the underlying technology shift from PMOS to NMOS to HMOS and beyond. Another issue is thinking that every vendor uses exactly the same generation labels, whereas the categorization is approximate. For exam purposes, it is enough to remember the broad pattern from smaller PMOS designs to larger, more integrated VLSI devices with increasing bit width. Final Answer: The correct answer is First generation microprocessors were 4 bit PMOS devices, second generation were 8 bit NMOS devices, third generation were 16 bit HMOS devices, and fourth generation were 32 bit and higher performance VLSI devices.

Question 10

On modern x86 CPUs, the so called real mode is a backward compatibility operating mode originally derived from which early Intel processor?

Accepted Answer

Introduction / Context: x86 processors support several operating modes, including real mode, protected mode, and long mode on newer chips. Real mode is a simple mode used during system startup and is compatible with very early software. This question asks from which original processor this mode is derived. Given Data / Assumptions: Real mode is associated with 16 bit addressing and simple segmentation. The Intel 8086 was the original 16 bit x86 processor and did not support protected mode. Later processors added protected mode and advanced features but kept real mode for backward compatibility. Concept / Approach: The 8086 introduced the basic x86 instruction set and used a 16 bit architecture with segmented addressing. When the 80286 introduced protected mode, Intel retained a mode that behaved like the older 8086 so that existing software would continue to run. This backward compatible mode became known as real mode. On modern x86 chips, the processor still starts in real mode to run firmware and boot loaders before switching to more advanced modes. Step-by-Step Solution: Step 1: Recall that the 8086 was the first in the x86 family and used 16 bit registers with segmented memory addressing.Step 2: Remember that it did not have protected mode or hardware memory protection features that came later.Step 3: When later CPUs such as the 80286 and 80386 were introduced, they needed to run old 8086 programs, so they preserved a compatibility mode.Step 4: This compatibility mode, which mimics the 8086 environment, is what is now called real mode. Verification / Alternative check: Technical manuals for x86 processors describe real mode as the mode where the CPU behaves like an 8086. Addressing is limited to 20 bit addresses constructed from 16 bit segment and offset values, leading to a one megabyte address space. There is no hardware enforced memory protection or privilege levels. These characteristics match the original 8086 design and confirm that real mode originates from that processor. Why Other Options Are Wrong: Option A: The 4004 is a much earlier 4 bit microprocessor that is not part of the x86 family and did not define real mode.Option C: The Pentium Pro is a much later, advanced superscalar processor that built on an already established x86 architecture; real mode predates it by many years.Option D: Real mode is clearly based on earlier architecture and is not a completely new design. Common Pitfalls: Some learners assume that real mode is a simplified mode invented later just for booting, rather than recognizing it as the original operating model of the 8086. Another confusion is mixing up the 8086 and 80286, where the 80286 introduced protected mode but still supported real mode for compatibility. Keeping the historical order clear helps when understanding how modern operating systems switch modes during startup. Final Answer: The correct answer is The 16 bit Intel 8086 processor, which did not have protected mode.

Question 11

In a typical microcomputer system, why is the address bus unidirectional while the data bus is bidirectional?

Accepted Answer

Introduction / Context: Microcomputer systems connect the central processing unit, memory, and peripheral devices using buses. Two key buses are the address bus and the data bus. Understanding why the address bus is unidirectional and the data bus is bidirectional helps clarify how information flows in a computer system. Given Data / Assumptions: The CPU generates addresses to select memory locations or I or O ports. Data can flow from the CPU to memory or from memory to the CPU. Buses are groups of signal lines that carry either addresses or data. Concept / Approach: The address bus carries the memory or I or O address that the CPU wants to access. The CPU is the master that initiates memory transactions, so it drives the address lines outward toward memory and I or O devices. There is no need for memory to send addresses back to the CPU, so the address bus can be unidirectional. The data bus, however, must support two way communication. When the CPU writes data, it drives the data bus toward memory or devices. When the CPU reads data, memory or devices drive the data bus in the opposite direction and the CPU reads the signals. Therefore, the data bus must be bidirectional. Step-by-Step Solution: Step 1: Consider a memory write. The CPU places an address on the address bus and data on the data bus and asserts control signals.Step 2: Memory hardware decodes the address and stores the data at the selected location. Memory does not send any address back.Step 3: Consider a memory read. The CPU again places an address on the address bus and asserts read control signals.Step 4: Memory decodes the address and places the requested data on the data bus, which flows back into the CPU. This requires the data bus to change direction. Verification / Alternative check: Hardware schematics often show address bus lines with arrows pointing from the CPU to memory and peripherals, confirming the unidirectional nature. Data bus lines usually have arrows at both ends or are drawn without arrows, indicating bidirectional flow. Tri state buffers or bus transceivers control which device is currently driving the data bus, confirming that it must support both directions. Why Other Options Are Wrong: Option B: Claims both buses must be bidirectional, which ignores the master role of the CPU in address generation.Option C: Incorrectly states that the address bus is shared with the control bus and must therefore be bidirectional; address and control buses are distinct.Option D: Says the data bus carries only addresses, which is false by definition; the data bus carries data values, not address values. Common Pitfalls: Students sometimes confuse which bus carries what type of information. Another common error is to think that memory might need to send addresses back to the CPU, but in a standard architecture the CPU is responsible for generating addresses. Understanding this division of roles makes it easier to analyze timing diagrams and design microprocessor based systems. Final Answer: The correct answer is Because the processor only sends addresses to memory and I or O devices, but both sends and receives data values, so the address bus is unidirectional while the data bus is bidirectional.

Question 12

In the Intel 8085 microprocessor, which hardware interrupt input is edge triggered rather than purely level sensitive?

Accepted Answer

Introduction / Context: The Intel 8085 microprocessor supports several hardware interrupts, each with different triggering characteristics and priority levels. Some interrupts are level sensitive, meaning they respond to a sustained logic level, while others are edge triggered, responding to a transition. Knowing which interrupt uses which triggering mechanism is important for interfacing external hardware correctly. Given Data / Assumptions: The 8085 has interrupt inputs such as TRAP, RST 7.5, RST 6.5, RST 5.5, and INTR. Most of these interrupts are level sensitive. One of them is primarily edge triggered. Concept / Approach: In the 8085, RST 7.5 is an edge triggered interrupt. It responds to a rising edge on its input signal. Once the edge is detected and the interrupt is acknowledged, the internal flip flop stores the request until it is serviced or cleared. In contrast, RST 6.5, RST 5.5, and INTR are level sensitive. TRAP has a combination of edge and level sensitivity but is usually described separately as a non maskable interrupt with special behavior. Standard exam questions focus on RST 7.5 as the clearly edge triggered input. Step-by-Step Solution: Step 1: Recall the list of vectored interrupts on the 8085: TRAP, RST 7.5, RST 6.5, and RST 5.5.Step 2: Remember that RST 7.5 latches the interrupt request on a rising edge, which is characteristic of edge triggering.Step 3: Recognize that RST 6.5 and RST 5.5 are level sensitive and require a high level to be present until acknowledged.Step 4: Match this knowledge to the option that identifies RST 7.5 as edge triggered. Verification / Alternative check: Reference materials for the 8085 state that RST 7.5 is a maskable, edge triggered interrupt with a higher priority than RST 6.5 and RST 5.5. Its internal flip flop captures the rising edge, which allows short pulses to be recognized even if they do not persist. This behavior distinguishes it from level sensitive inputs, which may be missed if the signal does not remain active long enough. Why Other Options Are Wrong: Option A: TRAP is a non maskable interrupt with a mixture of edge and level sensitivity, but the standard answer for purely edge triggered behavior in exam questions is RST 7.5.Option C: RST 6.5 is level sensitive, not edge triggered.Option D: RST 5.5 is also level sensitive. Common Pitfalls: Students sometimes confuse TRAP and RST 7.5 because both have special characteristics. Another common mistake is to assume that all RST interrupts behave the same way. Carefully reading the microprocessor documentation or a reliable textbook helps separate edge triggered inputs from level sensitive ones. Remembering that the seven in RST 7.5 can remind you of the edge triggered behavior is a useful mnemonic. Final Answer: The correct answer is RST 7.5 interrupt input, which is edge triggered.

Question 13

In the 8085 microprocessor, which pair of registers are the dedicated 16 bit registers used for sequencing and stack management?

Accepted Answer

Introduction / Context: The Intel 8085 microprocessor has several internal registers, including general purpose registers, the accumulator, and special purpose registers. Among these, the program counter and stack pointer are dedicated 16 bit registers used to control program flow and stack operations. This question checks your understanding of which registers have 16 bit width and what their roles are. Given Data / Assumptions: The 8085 has 8 bit general purpose registers and the accumulator. It also has two special 16 bit registers. We need to identify the correct pair of 16 bit dedicated registers. Concept / Approach: The program counter holds the 16 bit address of the next instruction to be fetched from memory. After each instruction fetch, the program counter is updated to point to the following instruction, unless a control transfer modifies it. The stack pointer holds the 16 bit address of the current top of the stack in memory. Push and pop operations adjust the stack pointer and use it to store or retrieve data from the stack region. Step-by-Step Solution: Step 1: Recall that the accumulator and general purpose registers are 8 bit wide in the 8085.Step 2: Recognize that the program counter must address any location in the 64 kilobyte memory space, which requires 16 bits.Step 3: Similarly, the stack pointer must be able to point into memory and is therefore a 16 bit register.Step 4: Match these facts to the option that lists program counter and stack pointer as the dedicated 16 bit registers. Verification / Alternative check: Technical descriptions of the 8085 architecture list the register set explicitly. The program counter and stack pointer are described as 16 bit registers, while other registers such as A, B, C, D, E, H, and L are 8 bit each. Although register pairs such as BC, DE, and HL can be used as 16 bit register pairs in some instructions, the question focuses on dedicated registers used for sequencing and stack management, which are PC and SP. Why Other Options Are Wrong: Option A: The accumulator is 8 bit, not 16 bit, so pairing it with the program counter is incorrect.Option C: Register H by itself is 8 bit. Only the HL pair can be used as a 16 bit register in some instructions, but HL is not a dedicated control register.Option D: The accumulator is not 16 bits wide; it is an 8 bit register used for arithmetic and logic operations. Common Pitfalls: Students sometimes confuse dedicated 16 bit registers with 8 bit registers that can be combined as pairs. While HL, DE, and BC pairs can hold 16 bit values in some instructions, they are not the same as the program counter and stack pointer, which always operate as 16 bit registers and have specific roles in controlling program flow and stack operations. Final Answer: The correct answer is Program Counter and Stack Pointer, which are dedicated 16 bit registers.

Question 14

Which of the following lists correctly matches examples of 8 bit, 16 bit, and 32 bit Intel microprocessors respectively?

Accepted Answer

Introduction / Context: Microprocessors are often classified by the width of their data paths and registers. Intel has produced famous 8 bit, 16 bit, and 32 bit processors that are widely studied in computer architecture courses. This question asks you to match the correct representative example for each bit width. Given Data / Assumptions: The Intel 8085 is a well known 8 bit microprocessor. The Intel 8086 is a 16 bit microprocessor. The Intel 80386 is a 32 bit microprocessor. Concept / Approach: The 8085 has 8 bit registers and an 8 bit data bus, but a 16 bit address bus. Therefore, it is classified as an 8 bit microprocessor. The 8086 has 16 bit registers and a 16 bit data bus, so it is a 16 bit device. The 80386 extended the x86 architecture to 32 bits and introduced 32 bit registers such as EAX and all the extended general purpose registers. The option that lists 8085, 8086, and 80386 in that order aligns with these classifications. Step-by-Step Solution: Step 1: Identify the 8 bit example. The 8085 is commonly taught as an 8 bit microprocessor.Step 2: Identify the 16 bit example. The 8086 has 16 bit registers and is described as a 16 bit processor.Step 3: Identify the 32 bit example. The 80386 is the first widely used 32 bit x86 processor.Step 4: Choose the option that lists these three devices in the correct order of 8 bit, 16 bit, and 32 bit. Verification / Alternative check: Checking Intel documentation confirms these classifications. The 8085 is 8 bit, the 8086 is 16 bit, and the 80386 is 32 bit. The 8088 is closely related to the 8086 but has an 8 bit external data bus. The 80286 is still 16 bit internally, despite enhancements. None of these details contradict the basic mapping used in this question. Why Other Options Are Wrong: Option B: Mislabels the 8086 as 8 bit and the 80286 as 32 bit, which is incorrect since both are 16 bit internally.Option C: Reverses the historical bit widths, incorrectly calling the 4004 a 32 bit device, which it is not.Option D: Misclassifies the 80386 as 8 bit and the 8085 as 32 bit, which is the opposite of their actual specifications. Common Pitfalls: Students sometimes confuse external bus width with internal register width. For example, the 8088 has an 8 bit external data bus but is internally similar to the 16 bit 8086. The classification usually refers to the internal data path width, not just the external bus. Keeping these distinctions clear makes it easier to answer classification questions correctly. Final Answer: The correct answer is 8085 (8 bit), 8086 (16 bit), 80386 (32 bit).

Question 15

In basic computer security, what is the most effective way for a typical user to prevent a computer virus from entering and infecting a personal computer system?

Accepted Answer

Introduction / Context: Computer viruses and other forms of malicious software can damage files, steal data, slow down systems, and spread to other machines on a network. This question tests your understanding of basic computer security best practices and how an ordinary user can most effectively reduce the chance of a virus entering and infecting a personal computer system. Given Data / Assumptions: - We are dealing with a typical home or office personal computer.- The question focuses on prevention of virus infection, not on removal after infection.- Several options describe different maintenance and usage habits, and we must choose the one that directly addresses malware prevention. Concept / Approach: Viruses usually enter through untrusted software, infected email attachments, malicious websites, and removable media. The most effective preventive approach combines technical protection with safe user behavior. A reputable antivirus solution with real time scanning and regularly updated virus signatures can detect many threats. Keeping the operating system and applications updated closes known security holes. Finally, avoiding suspicious attachments, links, and downloads reduces the chance of encountering new malware in the first place. General maintenance tasks such as defragmenting disks or cleaning fans are useful for performance and hardware health, but they do not stop viruses from entering the computer. Step-by-Step Solution: Step 1: Identify which option directly mentions antivirus software and security updates. Option A clearly talks about installing reputable antivirus software and keeping it updated.Step 2: Note that option A also mentions keeping the operating system updated and avoiding suspicious attachments and downloads, which are common infection vectors.Step 3: Evaluate option B. Turning off the monitor saves power but has no effect on whether malware can enter the system.Step 4: Evaluate option C. Using pirated software often increases the risk of infection, because such software may be modified with hidden malware.Step 5: Evaluate option D. Defragmenting the hard disk may improve performance on some systems but does not remove or block viruses.Step 6: Evaluate option E. Cleaning the fan and cabinet improves cooling but is unrelated to virus prevention.Step 7: Conclude that only option A provides a comprehensive and effective method to prevent viruses from entering the computer. Verification / Alternative check: Security guidelines from operating system vendors and security companies consistently recommend three pillars of protection: updated security software, patched systems, and cautious user behavior. These sources emphasize not opening unexpected attachments, not downloading unknown software, and keeping antivirus and system updates current. None of them claim that defragmentation, turning off monitors, or cleaning fans alone will prevent viruses, which confirms that option A is correct. Why Other Options Are Wrong: Option B affects only the display device, not the risk of malware. Option C is risky practice because pirated software may contain hidden malicious code. Option D helps performance but does not inspect or block files for malware. Option E relates to physical maintenance and cooling, which has no effect on whether a malicious program can enter the system or execute. Common Pitfalls: Many users wrongly assume that only installing an antivirus program once is enough, without keeping it updated or changing unsafe browsing habits. Others focus on general maintenance tasks like cleaning or defragmenting and neglect security updates. Remember that security is a continuous process that combines software tools and smart user behavior. Prevention is much easier than recovering from a large scale infection or data loss. Final Answer: The most effective preventive measure is to install reputable antivirus software, keep all software updated, and avoid suspicious downloads and email attachments as described in option A.

Question 16

In computer ergonomics and occupational health, the abbreviation RSI commonly stands for which condition that can be caused by repetitive computer use and poor posture?

Accepted Answer

Introduction / Context: Modern computer users spend long periods of time typing, using a mouse, and looking at screens. This question tests awareness of a common health term used in computer ergonomics and workplace safety. Knowing what RSI stands for helps users recognise health risks and motivates them to follow better posture and break habits. Given Data / Assumptions: - The acronym in question is RSI.- The context is computer hardware and usage, especially health effects from repetitive actions.- Only one option correctly expands the abbreviation as it is used in ergonomics. Concept / Approach: RSI is widely used in occupational health to describe a group of conditions affecting muscles, tendons, and nerves due to repetitive motions, awkward postures, or sustained static positions. In the context of computer work, repetitive typing, mouse use, and poor workstation setup can contribute to pain in the wrists, hands, arms, shoulders, or neck. The other expansions listed in the options sound technical but do not correspond to the standard health related meaning of RSI in this context. Step-by-Step Solution: Step 1: Recall common safety terms used in computer labs and office training sessions. RSI is almost always explained as Repetitive Strain Injury.Step 2: Compare this with option A, which exactly states Repetitive Strain Injury.Step 3: Examine option B, Random System Interrupt. While this phrase sounds related to operating systems and interrupts, it is not a standard acronym in this context.Step 4: Examine option C, Remote Server Interface, which could be a technical phrase but is not what RSI usually means in ergonomic discussions.Step 5: Examine option D, Rotational Speed Index, which might relate to motors or disks but not to human health.Step 6: Examine option E, Register Stack Initialization, which sounds like low level programming terminology, again not related to workplace injuries.Step 7: Conclude that only option A matches the commonly accepted health and safety expansion of RSI. Verification / Alternative check: Health and safety guidelines for office workers, national health service websites, and ergonomic training materials all define RSI as Repetitive Strain Injury. They list its symptoms and prevention strategies, such as adjusting chair height, using wrist supports, taking regular breaks, and performing stretching exercises. No authoritative health resource uses RSI to mean the other expansions listed in the options, confirming that option A is correct. Why Other Options Are Wrong: Option B refers loosely to computing concepts but does not match any standard acronym. Option C and option D also sound technical but are not established terms in this context. Option E is related to how registers might be initialised in processors but is not a recognised health condition. Thus, these options are distractors and should not be selected. Common Pitfalls: Learners who focus only on technical computing terms may forget that exam questions sometimes cover health, safety, and ergonomics as part of hardware awareness. Another pitfall is to assume that every acronym in a technical paper must refer to a hardware or software feature. In reality, understanding user health and safe working practices is an important part of computing education. Final Answer: In this context, RSI stands for Repetitive Strain Injury.

Question 17

In computer networking, how many bits are contained in a standard IPv4 address used on the Internet?

Accepted Answer

Introduction / Context: Internet Protocol version 4, commonly written as IPv4, is one of the core protocols that enable communication on the Internet. Understanding the size of an IPv4 address is fundamental for topics such as subnetting, address exhaustion, and the transition to IPv6. This question checks if you remember the basic length of an IPv4 address in bits. Given Data / Assumptions: - The question explicitly refers to IPv4, not IPv6.- We are asked about the number of bits in an IPv4 address.- Several possible bit lengths are offered as options, including powers of two and small values. Concept / Approach: An IPv4 address is traditionally written in dotted decimal form, such as 192.168.1.10, but internally it is a binary number. Each dotted decimal part represents 8 bits, also called an octet. There are four octets, so the total number of bits is 4 multiplied by 8. By converting this reasoning into a simple multiplication, we can find the total bit length and then match it with the correct option. Step-by-Step Solution: Step 1: Recall that an IPv4 address consists of four numerical fields separated by dots, for example A.B.C.D.Step 2: Each of these fields, or octets, can range from 0 to 255, which requires 8 bits to represent.Step 3: Compute the total number of bits as 4 * 8.Step 4: Perform the multiplication: 4 * 8 = 32 bits.Step 5: Match this result with the options. Option C states 32 bits.Step 6: Confirm that none of the other options match the known definition of IPv4 address length. Verification / Alternative check: Networking textbooks and standards documents describe IPv4 as a 32 bit address space. This is the basis for the total number of possible addresses, which is 2^32. Constraints and reserved ranges reduce the number of usable addresses, but the underlying bit length remains 32. By contrast, IPv6 uses 128 bit addresses, which are referenced in other contexts but not in this question. Why Other Options Are Wrong: Option A, 128 bits, corresponds to IPv6, not IPv4. Option B, 64 bits, and option D, 16 bits, do not match any standard IP version definition. Option E, 8 bits, would be far too small and could represent only 256 unique values, which is clearly insufficient for global addressing. Therefore these options are incorrect in the context of IPv4. Common Pitfalls: Some learners confuse IPv4 and IPv6 lengths, especially because IPv6 is often discussed alongside IPv4 in modern networking courses. Another pitfall is to think only in dotted decimal terms and forget that each octet is actually a group of 8 bits. Remembering that IPv4 uses four octets helps anchor the concept of 32 bit addresses in memory. Final Answer: A standard IPv4 address contains 32 bits.

Question 18

In computer hardware terminology, what is a microprocessor and how is it best described in relation to the overall computer system?

Accepted Answer

Introduction / Context: The microprocessor is the heart of most modern computers and embedded systems. This question checks your understanding of what a microprocessor actually is and how it fits into the architecture of a computer. Knowing this definition is a foundation for studying more advanced topics such as instruction sets, buses, and memory interfacing. Given Data / Assumptions: - The question asks for the best description of a microprocessor.- Several options describe different hardware components, some of which are unrelated to processing.- Only one option correctly matches the standard definition from computer architecture. Concept / Approach: A microprocessor is an integrated circuit that implements the central processing unit, including arithmetic logic, control unit, and registers, on a single chip. It executes instructions from memory and controls the operation of the entire system through buses and control signals. Other hardware devices such as disk drives, power supplies, and monitors are important, but they do not perform the general purpose instruction execution role that defines a microprocessor. Step-by-Step Solution: Step 1: Recall that the CPU is the component that fetches, decodes, and executes instructions, performing arithmetic and logical operations and controlling data flow.Step 2: In microprocessor based systems, the CPU functions are integrated onto a single chip, which is called the microprocessor.Step 3: Option A states that a microprocessor is a programmable integrated circuit containing the CPU on a single chip. This matches the standard definition.Step 4: Option B describes a mechanical backup device, which is more like a tape drive and not a processor.Step 5: Option C describes a magnetic disk drive, such as a hard disk, used for storage rather than processing.Step 6: Option D describes a power supply unit, which provides voltage but does not execute instructions.Step 7: Option E describes a display screen, which is an output device, not a processing unit. Verification / Alternative check: Computer architecture textbooks define a microprocessor as a VLSI (very large scale integration) chip that contains the arithmetic logic unit, registers, and control logic necessary to execute a stored program. Examples include Intel x86 processors and ARM processors. These sources clearly distinguish microprocessors from storage, power, and display devices, confirming that option A is the only correct description. Why Other Options Are Wrong: Option B confuses the concept with storage media. Option C describes secondary storage, which is important but not responsible for executing instructions. Option D is about power regulation, not computation. Option E refers to an output device that shows results but does not perform core calculations. None of these match the central processing role of a microprocessor. Common Pitfalls: Students new to hardware sometimes confuse terms such as CPU, microprocessor, microcontroller, and motherboard. It helps to remember that the microprocessor is the chip that performs generic computation, while a microcontroller often integrates a microprocessor core with memory and peripherals on a single chip. Peripheral devices such as disks and monitors support input, output, and storage rather than processing. Final Answer: A microprocessor is a programmable integrated circuit that contains the CPU of a computer on a single chip, as stated in option A.

Question 19

In the Intel 8085 microprocessor, which register pair is commonly referred to as the high order and low order register pair used together as a 16 bit register?

Accepted Answer

Introduction / Context: Understanding register organisation is essential when learning any microprocessor architecture. The Intel 8085 uses several 8 bit registers that can also be paired to form 16 bit register pairs. This question focuses on which pair is often called the high order and low order register pair, a term commonly used when addressing memory. Given Data / Assumptions: - The microprocessor in question is the Intel 8085.- The phrase high order and low order register pair refers to two 8 bit registers used together.- The options list different possible combinations of registers. Concept / Approach: In the 8085 microprocessor, several register pairs exist, such as BC, DE, and HL. The HL pair is special because it is often used as a 16 bit memory pointer, with H holding the high order 8 bits of an address and L holding the low order 8 bits. This is why these two registers are frequently referred to as the high order and low order registers. Other registers like A, B, D, and E are important for operations but are not specifically given this high order and low order terminology in standard teaching materials. Step-by-Step Solution: Step 1: Recall that the 8085 has six general purpose 8 bit registers: B, C, D, E, H, and L, as well as the accumulator A.Step 2: These can be paired as BC, DE, and HL to form 16 bit registers for certain instructions.Step 3: The HL pair is heavily used for memory addressing, where H stores the higher 8 bits of the memory address and L stores the lower 8 bits.Step 4: Due to this usage, many texts describe H as the high order register and L as the low order register.Step 5: Option A explicitly mentions the H and L register pair as a 16 bit memory pointer, which fits the description.Step 6: Options B, C, D, and E either refer to different register combinations or to concepts that are not labelled high order and low order in standard 8085 documentation. Verification / Alternative check: When examining 8085 instruction examples, you will often see the HL pair used with instructions like MOV M, A or LXI H, address. These show that HL points to memory, with H forming the high part and L forming the low part of the address. Reference books on 8085 microprocessor architecture also refer to the HL pair as the high order and low order pair, confirming the correctness of option A. Why Other Options Are Wrong: Option B pairs A and B, but A is the accumulator and not normally paired with B as a 16 bit register. Option C refers to DE but incorrectly restricts its use to input output, which is not accurate. Option D pairs the program counter and stack pointer, which are separate 16 bit registers and not referred to as a single high order low order pair. Option E combines the accumulator and flag register, which together form the program status word but are not described as high and low order registers in the same sense. Common Pitfalls: Some learners mix up the various register pairs or think that any two registers used together can be called high and low order. It is helpful to remember that this specific phrase is typically reserved for the HL pair because of its special role in memory addressing. Drawing diagrams of the 16 bit address and labelling which register holds which part can make this much clearer. Final Answer: In the 8085 microprocessor, the high order and low order register pair is the H and L register pair, used together as a 16 bit memory pointer.

Question 20

In microprocessor architecture, what is the program counter register and what is its main function during program execution?

Accepted Answer

Introduction / Context: The program counter is one of the most important registers in any microprocessor or CPU. This question checks whether you understand what the program counter is and how it controls the flow of execution in a program. Without a correct understanding of the program counter, it is difficult to grasp how instructions are fetched and executed in sequence. Given Data / Assumptions: - The term program counter refers to a CPU register.- We are asked about its definition and main function.- The options propose several different roles that a register or counter might have. Concept / Approach: The program counter, often abbreviated as PC, is a special purpose register that keeps track of the address in memory of the next instruction to be fetched for execution. After the CPU fetches an instruction, the program counter is usually incremented or updated to point to the subsequent instruction, unless a branch, jump, or call modifies it. This mechanism allows the CPU to step through a program in a controlled way. Other registers store data, flags, or other information, but the program counter specifically holds instruction addresses. Step-by-Step Solution: Step 1: Recall that instruction execution follows a cycle of fetch, decode, and execute.Step 2: During the fetch phase, the CPU needs to know from which memory location to read the next instruction.Step 3: The program counter provides this address. The address stored in the PC is placed on the address bus so that the memory can supply the instruction.Step 4: After the instruction is fetched, the CPU updates the program counter to the next address or to a target address in the case of branches and jumps.Step 5: Option A exactly describes this role, stating that the program counter holds the address of the next instruction to be fetched and executed.Step 6: Options B, C, D, and E refer to other possible uses of registers but do not match this essential control function. Verification / Alternative check: Computer architecture diagrams always show the program counter feeding the address lines during the instruction fetch phase. Assembly language examples show how branch and jump instructions modify the program counter to alter control flow. These consistent descriptions across textbooks confirm that the core function of the program counter is to hold the address of the next instruction, as given in option A. Why Other Options Are Wrong: Option B describes a register that would act as an accumulator or result register, not the program counter. Option C resembles a hardware event counter that might record external pulses, which is different from the PC. Option D describes nonvolatile memory, but the program counter is a volatile register. Option E is incorrect because the program counter does not always contain zero; its value changes throughout program execution to track instruction addresses. Common Pitfalls: A common error is to confuse the program counter with the instruction register, which holds the current instruction, or with general purpose registers that store data. Remember that the program counter is tied to memory addressing and control flow, not to holding computation results. Visually tracing through a simple assembly program and observing how the program counter changes can help make this concept concrete. Final Answer: The program counter is a register that holds the address of the next instruction to be fetched and executed by the CPU.

Hardware Questions