Question 1

Compiler backend responsibility:  In storage assignment during compilation/assembly, which tasks are performed to prepare memory for a program’s execution?

Accepted Answer

Introduction / Context: Storage assignment (or memory layout) is a core phase in compilation/assembly that maps program entities to addresses or offsets. Proper layout ensures correct access at runtime, efficient use of memory, and support for calling conventions and data initialization. Given Data / Assumptions: We handle variables, temporaries, and literals. Both compile-time and link-time allocation may be involved. Initialization of static data is required before execution begins. Concept / Approach: The compiler/assembler allocates storage for global/static data, arranges stack frames for locals and temporaries, and places constants in literal pools or read-only segments. It also emits initialization records so the loader/runtime can set appropriate initial values before main executes. Step-by-Step Solution: Assign addresses/offsets for variables according to scope and lifetime.Reserve slots for intermediate results and temporaries in registers or stack.Create literal pools/RO sections and arrange for initialization data.Therefore, all listed tasks fall under storage assignment responsibilities. Verification / Alternative check: Standard compiler architecture references list symbol table management, stack frame layout, and data segment/literal pool generation as part of storage assignment and code generation. Why Other Options Are Wrong: Each single option is only a subset; real systems require all three. None of the above is false because these are indeed performed. Common Pitfalls: Overlooking alignment and padding; confusing static initialization (loader) with dynamic initialization (constructor code); ignoring register allocation’s impact on temporary storage. Final Answer: all of the above

Question 2

Systems software on microcomputers: Which of the following are examples of operating system or system-level software commonly used on microcomputers (personal computers)?

Accepted Answer

Introduction / Context: System software is the foundational software that manages hardware resources, provides core services, and offers an interface for application software. On microcomputers, classic examples include various disk operating systems and Unix-like operating systems. This question checks recognition of standard system software used historically and presently on PCs. Given Data / Assumptions: The platforms referenced are microcomputers (personal computers). MS-DOS and PC-DOS are DOS-family operating systems. Unix is a multiuser, multitasking operating system family with PC ports and derivatives. Concept / Approach: System software includes the operating system (OS), device drivers, utility programs closely tied to hardware, and firmware interfaces. MS-DOS (by Microsoft) and PC-DOS (by IBM) were widely used on early IBM PC-compatible systems. Unix and its variants (including modern Unix-like systems) have also run on microcomputers, providing multitasking, multiuser capabilities, and rich networking stacks. Step-by-Step Solution: Identify whether each choice is system software: MS-DOS = OS, PC-DOS = OS, Unix = OS.Confirm that all three satisfy the definition of system software on microcomputers.Therefore the inclusive option is correct. Verification / Alternative check: Historical PC documentation lists MS-DOS/PC-DOS as default OSes on IBM PCs and compatibles. Numerous PC ports of Unix (e.g., Xenix, BSD variants, SCO, and later Unix-like systems) demonstrate Unix as system software on microcomputers. Why Other Options Are Wrong: MS-DOS, PC-DOS, Unix (individually): Each is correct but incomplete; the question asks which are examples, and all are. None of the above: Incorrect because all listed are valid examples. Common Pitfalls: Confusing application software (word processors, spreadsheets) with system software; assuming Unix is only for mainframes or servers (it also exists on PCs). Final Answer: All of the above

Question 3

Classical synchronization problem: The Producer–Consumer problem can be solved using which synchronization constructs or mechanisms?

Accepted Answer

Introduction / Context: The Producer–Consumer problem is a canonical concurrency challenge where producers generate data and consumers process it while sharing a bounded buffer. The aim is to prevent race conditions, buffer overflows, and starvation. Multiple synchronization abstractions solve this problem. Given Data / Assumptions: A bounded buffer exists between producers and consumers. Correctness requires mutual exclusion on the buffer and coordination on its empty/full state. We are evaluating well-known OS/concurrency mechanisms. Concept / Approach: Semaphores (counting and binary) can enforce mutual exclusion (mutex) and signal buffer space or data availability. Event counters (and condition variables) can coordinate wakeups when buffer states change. Monitors encapsulate shared data and operations with implicit mutual exclusion and condition variables for waiting/signaling on buffer-full or buffer-empty conditions. Step-by-Step Solution: Recognize that the problem needs both mutual exclusion and condition synchronization.Semaphores: use one mutex semaphore plus two counting semaphores (empty and full).Event counters or condition variables: wait/signal on buffer-empty/full states inside protected regions.Monitors: define put/get methods with wait/signal, providing structured synchronization. Verification / Alternative check: Reference solutions in operating systems textbooks show working implementations using any of the listed abstractions, proving all are valid approaches. Why Other Options Are Wrong: semaphores, event counters, monitors (individually): Each is acceptable but incomplete; the comprehensive answer is that all listed can solve it. None of the above: Incorrect, because each offered mechanism is suitable when applied correctly. Common Pitfalls: Deadlocks due to incorrect semaphore ordering; missed signals; failing to bound the buffer or protect access with mutual exclusion. Final Answer: all of the above

Question 4

Virtual memory sizing: A program uses 16-bit virtual addresses. If the page size is 0.5 KB (that is, 512 bytes), how many pages exist in the virtual address space?

Accepted Answer

Introduction / Context: Paging divides an address space into fixed-size pages. The number of virtual pages depends on total virtual address space size and the page size. This question tests the ability to convert address bits and page size to the number of pages. Given Data / Assumptions: Virtual address width = 16 bits. Page size = 0.5 KB = 512 bytes. 1 KB = 1024 bytes. Concept / Approach: Total virtual address space equals 2^address_bits bytes. The number of pages equals total virtual bytes divided by bytes per page. With a power-of-two page size, the result is also a power of two. Use exponents to simplify division. Step-by-Step Solution: Compute total virtual space: 2^16 bytes = 65536 bytes.Compute page size in bytes: 0.5 KB = 512 bytes = 2^9 bytes.Number of pages = total bytes / page size = 2^16 / 2^9 = 2^(16 - 9).2^(16 - 9) = 2^7 = 128 pages. Verification / Alternative check: Alternative: Determine page offset bits equal to log2(512) = 9 bits. The remaining 16 - 9 = 7 bits form the virtual page number. 7 bits index 2^7 = 128 pages. Both methods agree. Why Other Options Are Wrong: 16, 32, 64: These correspond to 2^4, 2^5, 2^6 and would imply different address widths or page sizes; they do not match 16-bit with 512-byte pages. None of the above: Incorrect because 128 is valid. Common Pitfalls: Confusing KB with 1000 bytes; forgetting that 0.5 KB equals 512 bytes; mixing up page offset bits with page number bits. Final Answer: 128

Question 5

Software category identification: Software that measures, monitors, analyzes, and controls real-world (physical) events is referred to as what type of software?

Accepted Answer

Introduction / Context: Real-world control applications—industrial control, avionics, medical devices—must respond to inputs within strict timing constraints. The software that interacts with sensors and actuators to meet deadlines is real-time software. This question distinguishes it from other categories. Given Data / Assumptions: The software measures, monitors, analyzes, and controls physical processes. Timeliness and determinism are essential attributes. Examples include PLC systems, RTOS-based controllers, and embedded control loops. Concept / Approach: Real-time software operates under deadlines, often using a real-time operating system (RTOS). It emphasizes predictability over throughput—meeting worst-case execution time and jitter constraints. System software is broader and not necessarily time-constrained. Scientific software focuses on computation/analysis but is not inherently deadline-driven. Business software typically supports transactions, reporting, and workflows. Step-by-Step Solution: Identify key descriptors: monitoring and controlling real events implies I/O with deadlines.Map descriptors to categories: real-time software fits best.Confirm by examples: flight control, automotive ECUs, process control. Verification / Alternative check: RTOS documentation stresses deterministic scheduling (rate-monotonic, earliest-deadline-first) and bounded interrupt latencies, aligning perfectly with the description. Why Other Options Are Wrong: system software: Includes OS and utilities, not necessarily real-time. scientific software: Emphasizes numerical computation; timing may be flexible. business software: Office suites, ERPs; not for controlling real-time processes. None of the above: Incorrect because real-time software is standard terminology. Common Pitfalls: Assuming any embedded software is real-time—some embedded systems are not deadline-critical; conflating high performance with deterministic timing. Final Answer: real-time software

Question 6

Binary semaphore for mutual exclusion: To ensure that only one of many processes enters its critical section at a time, what should be the initial value of the controlling semaphore?

Accepted Answer

Introduction / Context: Semaphores are fundamental synchronization primitives. For mutual exclusion (mutex), a binary semaphore controls access to a critical section so that only one process can execute inside at once. The initial value determines whether the first process can enter immediately. Given Data / Assumptions: Multiple processes contend for the same critical section. Semaphore P (wait) decrements; V (signal) increments. Binary semaphore is used for mutual exclusion. Concept / Approach: A binary semaphore initialized to 1 indicates the resource (critical section) is free. The first P operation decrements it to 0 and grants entry. Additional P attempts block until the semaphore is signaled (V) by the process on exit, restoring it to 1. Initializing to 0 would block everyone at start, requiring an extra signal to begin. Step-by-Step Solution: Choose a binary semaphore for exclusivity.Initialize semaphore = 1 to allow first entrant.Processes call P before entering; only one succeeds at a time.On exit, process calls V to wake the next waiting process. Verification / Alternative check: Standard textbooks define mutex semaphores with initial value 1. Code examples show semaphore value toggling between 0 and 1 during use. Why Other Options Are Wrong: 8 or 16: These would allow many simultaneous entrants (counting semaphore), not mutual exclusion. 0: Would block all processes initially until an external V occurs. None of the above: Incorrect because 1 is correct. Common Pitfalls: Using counting semaphores unintentionally; forgetting to signal on exit leading to deadlock; initializing to 0 and wondering why no process proceeds. Final Answer: 1

Question 7

MS-DOS disk preparation: Which MS-DOS command divides the surface of a blank floppy disk into sectors and assigns a unique address to each one (creating the file system structures)?

Accepted Answer

Introduction / Context: Preparing a blank floppy for use requires creating the file system and logical structures that the operating system understands. In DOS, this operation is triggered by a specific utility command. Given Data / Assumptions: We have a blank floppy disk. We need to generate sectors, directory structures, and a file allocation table recognizable by DOS. We are choosing among common DOS commands. Concept / Approach: The DOS FORMAT command performs high-level formatting, building the boot sector, FAT(s), root directory, and marking logical sector structures. On some hardware it also performs low-level formatting (older controllers), but generally DOS FORMAT prepares the media with the proper file system layout. VER displays DOS version; CHKDSK checks the disk and reports status; there is no separate FAT command to format disks. Step-by-Step Solution: Insert blank media and run FORMAT (e.g., FORMAT A:).FORMAT writes the boot record, FATs, and root directory and verifies sectors.The disk becomes ready for file storage and program execution (if made system bootable). Verification / Alternative check: After running FORMAT, DOS reports capacity and allocation unit size; directory listing shows an empty, initialized file system. CHKDSK thereafter reports filesystem details instead of “unformatted”. Why Other Options Are Wrong: FAT command: No such standard DOS command; FAT is a structure. VER: Only shows DOS version. CHKDSK: Checks/repairs; does not create the file system structures from scratch. None of the above: Incorrect because FORMAT is right. Common Pitfalls: Confusing low-level vs. high-level formatting; accidentally formatting the wrong drive; forgetting the /S switch or equivalent to make a disk bootable (legacy behavior). Final Answer: FORMAT command

Question 8

Paging trade-offs: Which of the following statements about page size and paging performance is FALSE?

Accepted Answer

Introduction / Context: Choosing a page size affects memory overhead, fragmentation, locality, and I/O efficiency. Understanding these trade-offs helps in OS and architecture design and in tuning applications for systems with different page sizes. Given Data / Assumptions: Internal fragmentation occurs when allocated space exceeds requested space inside a fixed-size unit. Page table size grows with the number of pages. Larger I/O blocks can amortize overhead, often improving throughput. Concept / Approach: Smaller pages reduce internal fragmentation because wasted space per allocated page decreases. However, smaller pages increase the number of pages needed to cover an address space, increasing page table size and TLB pressure. Bigger pages improve sequential disk I/O efficiency but may bring in unnecessary data and instructions, potentially increasing cache and memory bandwidth waste. Step-by-Step Reasoning: Evaluate option A: Smaller pages imply more pages; thus larger page tables. True.Evaluate option B: Smaller pages reduce, not increase, internal fragmentation. False (therefore the correct choice).Evaluate option C: Larger pages fetch more contiguous data; some may be unused. True.Evaluate option D: Larger transfer sizes often yield better I/O efficiency. True. Verification / Alternative check: OS literature and performance studies confirm the general relationships: small pages reduce internal waste but increase metadata overhead; large pages improve I/O and TLB reach but can cause overfetch. Why Other Options Are Wrong: A: Correct statement—page tables grow with smaller pages. C: Correct—overfetch happens with large pages. D: Correct—larger, aligned I/O transfers are typically more efficient. None of the above: Incorrect since B is false. Common Pitfalls: Confusing internal with external fragmentation; assuming larger pages always improve performance (they may hurt locality for sparse accesses). Final Answer: internal fragmentation is increased with small pages

Question 9

I/O performance diagnostics: In operating system/device performance monitoring, what is “seeks analysis” typically used to diagnose?

Accepted Answer

Introduction / Context: Rotating-disk storage (HDD) performance is heavily influenced by seek operations—the movement of the read/write head between tracks. Excessive seeking increases service time and can cause the device to be saturated (“device busy”). Seeks analysis focuses on this component of I/O latency. Given Data / Assumptions: Traditional DASD/HDDs incur seek time, rotational latency, and transfer time. High seek rates indicate non-sequential access patterns or contention. Control-unit busy refers to controller saturation, a different bottleneck. Concept / Approach: Monitoring tools break down I/O waiting into components. Seeks analysis correlates workloads with head movement metrics to highlight random access patterns, poor locality, or queue contention. When seeks dominate, the device itself is frequently busy moving heads rather than transferring data, pointing to a device busy problem. Step-by-Step Reasoning: Identify what “seeks” measure: head repositioning events on disk.Relate high seek counts/latency to device saturation.Conclude that seeks analysis is primarily about device busy conditions rather than paging or controller saturation specifically. Verification / Alternative check: Storage performance reports (e.g., iostat-like tools, vendor utilities) show seek/queue depth metrics; sustained high values correlate with device busy rather than control-unit bottlenecks. Why Other Options Are Wrong: Paging problems: Though paging can generate I/O, seeks analysis targets disk head motion, not specifically virtual memory policy. Control-unit busy: That is a controller-level bottleneck; seeks analysis is about the device’s mechanical activity. Only real-time displays: Analysis can be historical, not just real-time. None of the above: Incorrect because device busy analysis fits. Common Pitfalls: Assuming all I/O latency equals seek time; ignoring SSDs where seek time is negligible; confusing queueing delays with seek latency. Final Answer: is used for analyzing device busy problems

Question 10

OS scheduling terms: In a multitasking operating system, what is the role of the dispatcher in relation to getting tasks onto the CPU?

Accepted Answer

Introduction / Context: Scheduling is a two-part process: a scheduler chooses which runnable task should execute next based on policy, and a dispatcher performs the low-level context switch to start that task on the CPU. Understanding this distinction is important for OS design and troubleshooting latency. Given Data / Assumptions: The system has a ready queue of runnable tasks. The scheduler has selected a next task (according to policy like priority, fairness, deadlines). The dispatcher executes the mechanics of switching contexts. Concept / Approach: While the high-level decision (“which task next?”) is the scheduler’s responsibility, the dispatcher handles the actual context switch: saving the current context, loading the chosen task’s context, updating CPU registers, and transferring control. In many texts, this concrete act is described as “dispatching” the process to the processor, i.e., actually getting it onto the CPU. Step-by-Step Reasoning: Identify terms: scheduler = policy; dispatcher = mechanism.Dispatcher performs the context switch and CPU hand-off.Therefore, it “actually schedules” (dispatches) the task into the processor. Verification / Alternative check: OS textbooks and kernel code separate pick-next-task (scheduler) and context_switch (dispatcher). Traces show the dispatcher enabling the selected task to run on the CPU. Why Other Options Are Wrong: Puts tasks in I/O wait: I/O wait is a task state change due to I/O, not the dispatcher’s job. Is always small and simple: Implementation detail; not universally true. Never changes task priorities: Dispatcher does not manage priorities; but “never” statements are risky—policies may interact during dispatch. None of the above: Incorrect because the dispatcher does hand tasks to the CPU. Common Pitfalls: Conflating the scheduler’s decision-making with the dispatcher’s context-switching; assuming the dispatcher manages priorities or I/O states. Final Answer: actually schedules the tasks into the processor

Question 11

Use cases for encryption: In practice, which type of network has historically relied most on data encryption to protect the confidentiality and integrity of transactions?

Accepted Answer

Introduction / Context: Data encryption is essential for protecting information in transit and at rest. While modern practice uses encryption everywhere, some sectors have historically been early and heavy adopters due to regulatory and risk considerations—most notably financial networks. Given Data / Assumptions: We consider practical, historical usage trends in industry. Financial transactions require confidentiality, integrity, and non-repudiation. Public and private networks can both use encryption. Concept / Approach: Banking and payment systems (e.g., interbank transfers, ATM networks, card networks) have long mandated strong cryptographic controls to prevent fraud and meet compliance standards. While public networks (like the Internet) now commonly use TLS, the question targets which domain was predominantly associated with encryption usage—the financial sector. Step-by-Step Reasoning: Identify sectors with strict security/compliance: finance is foremost.Assess claims: “mostly used by public networks” is too broad; encryption is used by both public and private networks.Reject impossibility or irrelevance claims (cannot be used by private; not necessary).Select financial networks as the best answer. Verification / Alternative check: Industry standards (e.g., PCI DSS) and banking regulations historically mandated encryption for sensitive data long before ubiquitous HTTPS became standard on public networks. Why Other Options Are Wrong: Mostly used by public networks: Encryption is common on both public and private networks; the statement is not specific or historically accurate. Cannot be used by private installations: False; private networks do use encryption. Not necessary: False; data can be intercepted without encryption. None of the above: Incorrect because financial networks is the best-supported choice. Common Pitfalls: Assuming encryption is only for Internet traffic; overlooking sector-specific mandates in finance, healthcare, and government. Final Answer: is mostly used by financial networks

Question 12

CPU scheduling fundamentals – Shortest Job First (SJF) In the SJF scheduling algorithm, which job is selected to execute next from the ready queue?

Accepted Answer

Introduction / Context: SJF (Shortest Job First) is a classic CPU scheduling algorithm used in operating systems to minimize average waiting time by always running the process with the shortest next CPU burst. This concept appears in OS design, performance engineering, and interview questions on scheduling strategies. Given Data / Assumptions: SJF chooses among ready processes based on predicted or known CPU burst length. All jobs are assumed to be in the ready queue and comparable by their expected CPU time. We are referring to non-preemptive SJF unless otherwise noted; preemptive SJF is often called Shortest Remaining Time First (SRTF). Concept / Approach: SJF minimizes the average waiting time by selecting the job that will finish the soonest, given its CPU burst length. If burst times are known exactly, SJF is provably optimal for average waiting time. In practice, burst times are estimated using exponential averaging or other heuristics derived from past behavior. Step-by-Step Solution: Define the selection rule: choose the job with the smallest next CPU burst.Compare each option to this rule.Identify that the correct rule matches the job “with the least processor needs.”Conclude that SJF does not prioritize arrival order or time spent waiting; it prioritizes burst length. Verification / Alternative check: Construct a small example with three jobs having CPU bursts 2, 4, and 8 units. Applying SJF (pick 2 first) yields lower average waiting time than FIFO (arrival order) or LIFO. Why Other Options Are Wrong: Last entered/first entered (options a and b) describe stack/queue discipline, not SJF. Longest waiting (option c) resembles aging or fair queueing, not SJF. “None of the above” is incorrect because one option matches exactly. Common Pitfalls: Confusing SJF with SRTF; assuming SJF uses arrival time; overlooking starvation risk for long jobs (often mitigated by aging). Final Answer: with the least processor needs.

Question 13

Why many microcomputer operating systems are called “Disk Operating Systems” Apple DOS, MS-DOS, and PC-DOS are termed disk operating systems primarily because:

Accepted Answer

Introduction / Context: Early microcomputer operating systems were commonly known as “Disk Operating Systems” (DOS) because of how they were distributed, loaded, and what they managed. Understanding this naming clarifies both historical usage and the role disks played in personal computing. Given Data / Assumptions: Examples include Apple DOS, MS-DOS, and PC-DOS. These systems boot from and manage disk-based storage (floppy or hard disks). The focus is on the origin and primary reason for the term “disk.” Concept / Approach: The phrase “Disk Operating System” reflects two connected ideas: the OS was distributed and loaded from disk, and it provided file system and device management specifically for disk media. In contrast, earlier systems booted from ROM or tape; DOS emphasized disk-based filesystems, directories, and utilities. Step-by-Step Solution: Identify the key distinguishing factor: system is stored and booted from disk.Relate DOS utilities to disk management (FORMAT, FDISK, DIR, COPY, etc.).Select the option that directly states the reason: “they are initially stored on disk.” Verification / Alternative check: Historical manuals show DOS loading from floppy disks into RAM and providing disk file management. MS-DOS and PC-DOS install and boot from disk partitions with BIOS support. Why Other Options Are Wrong: “Memory resident” is a property of execution, not the naming basis. “Available on magnetic tapes” was not the defining characteristic. “Partly in memory and partly on disk” is generic and not unique to DOS. Common Pitfalls: Assuming DOS is named solely for file management rather than the practical distribution/boot medium; conflating ROM-based systems with disk-loaded ones. Final Answer: they are initially stored on disk.

Question 14

Decision tables in software specification Which statement is NOT true about decision tables as a way to specify complex logic?

Accepted Answer

Introduction / Context: Decision tables are a compact way to represent complex conditional logic. Analysts and testers use them to ensure complete coverage of combinations and to communicate requirements clearly between stakeholders and developers. Given Data / Assumptions: Decision tables express conditions and actions in tabular form. They are human-readable artifacts for design and testing. They may be translated into executable code but are not inherently executable. Concept / Approach: Decision tables aid clarity and maintainability. However, they are specification formats, not programming languages. Computers do not “directly” execute a generic decision table unless a specialized rule engine or generator translates it into code or an executable rule set first. Step-by-Step Solution: Evaluate “easy to modify”: Generally true—changing a column/row updates a single rule.Evaluate “easy to understand”: True—conditions and actions are visually aligned.Evaluate “directly understood by the computer”: False in general; needs translation or tooling.Pick the statement that is not true: the one claiming direct computer understanding. Verification / Alternative check: In practice, teams convert decision tables into if-else chains, switch-case logic, lookup tables, or rule engine configurations before execution. Why Other Options Are Wrong: Options a and c describe recognized benefits. “All of the above” cannot be correct because one statement is false. “None of the above” is also incorrect because there is indeed one false statement. Common Pitfalls: Assuming a modeling notation implies executability; overlooking the need for traceable conversion to code or tests. Final Answer: A decision table is directly understood by the computer.

Question 15

Understanding multiprogramming in operating systems Which statement best describes multiprogramming?

Accepted Answer

Introduction / Context: Multiprogramming is a foundational concept in operating systems. It aims to improve CPU utilization by keeping several programs in memory at once so the CPU can switch to another when one blocks (for I/O, for example). Given Data / Assumptions: “Core” refers to main memory in historical terminology. Multiple programs may be in memory simultaneously. Scheduling and memory management cooperate to keep the CPU busy. Concept / Approach: Multiprogramming contrasts with single-program systems where the CPU can be idle during I/O. By loading multiple programs into separate memory regions, the OS can switch execution to another ready program, increasing throughput. Paging (option a) and address space (option b) are related but different concepts. Time allocation (option c) describes CPU scheduling rather than the memory-resident aspect of multiprogramming. Step-by-Step Solution: Identify definition: several programs are kept in memory simultaneously.Relate to CPU utilization: switch to another program when one waits.Select the option matching this: programs reside in separate memory areas at the same time. Verification / Alternative check: Classic OS texts define multiprogramming as having multiple processes in memory to maximize CPU utilization; time-sharing extends this with rapid preemption for interactivity. Why Other Options Are Wrong: (a) describes paging; (b) describes the address space; (c) addresses CPU scheduling, not the memory-resident aspect. Hence (d) is correct. Common Pitfalls: Confusing multiprogramming with multitasking/time-sharing; assuming preemption is required (early multiprogramming could be cooperative). Final Answer: allows multiple programs to reside in separate areas of core at the time.

Question 16

Boot processes – initializing a microcomputer with its operating system What is the term for the process of loading and initializing the operating system on a microcomputer?

Accepted Answer

Introduction / Context: Every computer session begins with a boot process: firmware performs hardware checks and loads the operating system into memory. Understanding terminology helps in support and troubleshooting. Given Data / Assumptions: We refer to the general act of loading and starting the OS. Cold vs warm boot are specific variants of booting. The question asks for the generic name of the process. Concept / Approach: “Booting” (from “bootstrap”) is the general term for starting a computer and loading the OS. A “cold boot” starts from power-off; a “warm boot” restarts without removing power. Both are types of booting but the umbrella term is simply “booting.” Step-by-Step Solution: Identify the general process: initialize hardware, locate boot device, load OS.Map terminology: booting is the broad term; cold/warm specify context.Choose the general term requested by the question: “Booting.” Verification / Alternative check: PC firmware guides and OS documentation refer to the process as “boot” or “boot sequence,” with qualifiers (cold/warm) when needed. Why Other Options Are Wrong: Cold booting and warm booting are subtypes, not the general term. “Boot recording” is unrelated. Hence “Booting” is the best fit. Common Pitfalls: Assuming the question wants the subtype; ignoring that both cold and warm are correct only in specific contexts. Final Answer: Booting.

Question 17

VSAM organizations – identifying dataset types Which of the following are valid file organization components of an IBM VSAM file?

Accepted Answer

Introduction / Context: VSAM (Virtual Storage Access Method) is an IBM mainframe file access method that supports multiple dataset organizations tailored to different access patterns and key structures. Given Data / Assumptions: Common VSAM organizations include KSDS, ESDS, and RRDS. Each organization suits particular workloads (keyed, sequential, or relative access). The options list these acronyms in expanded form. Concept / Approach: KSDS (Keyed Sequential Data Set) supports key-based access and sequential processing; ESDS (Entry Sequential Data Set) supports strictly sequential access by entry order; RRDS (Relative Record Data Set) uses relative record numbers for direct access. All are standard VSAM organizations. Step-by-Step Solution: Match each option to a recognized VSAM type: RRDS, KSDS, ESDS.Since all three are valid, select “all of the above.” Verification / Alternative check: IBM documentation enumerates KSDS, ESDS, and RRDS as the three principal VSAM dataset organizations (plus LDS in later contexts). Why Other Options Are Wrong: Each individual option names a valid VSAM type, so “None of the above” is incorrect; “all of the above” is the only fully correct aggregate choice. Common Pitfalls: Confusing ESDS (entry order) with purely sequential flat files outside VSAM; forgetting the existence of RRDS with fixed slots addressed by relative number. Final Answer: all of the above.

Question 18

Compiler design – permanent vs. transient tables In the general model of a compiler, which of the following is a permanent database (i.e., not rebuilt for each compilation)?

Accepted Answer

Introduction / Context: Compilers maintain a variety of tables while translating source code. Some are permanent parts of the compiler's definition of a language, whereas others are created afresh for each compilation unit. Given Data / Assumptions: Literal and identifier tables are populated from the current program. Source code is input, not a compiler database. The terminal table lists the language’s tokens (keywords, operators, punctuation). Concept / Approach: The terminal table is a permanent specification of the language's alphabet (token types) known to the compiler. In contrast, the identifier table (symbol table entries for user-defined names) and literal table (constants found in the program) are transient and rebuilt for each compilation. Step-by-Step Solution: Classify each option: terminals (language-defined) vs program-specific data (identifiers, literals).Identify permanence: terminal set is fixed for the language and resides with the compiler.Pick “Terminal Table.” Verification / Alternative check: Compiler textbooks describe lexical analysis using a DFA over the terminal set; the definition of terminals is part of the language specification and persists across compilations. Why Other Options Are Wrong: Literal/identifier tables are populated per source file or per build; source code is not a compiler database. Therefore, only the terminal table fits the “permanent” description. Common Pitfalls: Confusing the symbol table (which can be persisted by IDEs) with the permanent language tables inside the compiler; overlooking reserved word tables as part of terminals. Final Answer: Terminal Table.

Question 19

Compiler phases – understanding the Syntax (parsing) phase Which option correctly states the main function of the Syntax phase of a compiler?

Accepted Answer

Introduction / Context: Compilers operate in phases. After lexical analysis produces tokens, the syntax phase (parsing) organizes tokens into grammatical structures, ensuring the program conforms to the language grammar and producing an intermediate representation for later stages. Given Data / Assumptions: Lexical analysis precedes syntax analysis and outputs tokens. Syntax analysis validates structure against grammar. Intermediate representation (IR) is often built during or right after parsing. Concept / Approach: The syntax phase recognizes constructs such as expressions, statements, and declarations. It constructs a parse tree or abstract syntax tree and triggers semantic or IR-building actions. Building identifier/literal tables and tokenization are tasks of the lexical phase, not the syntax phase. Step-by-Step Solution: Map tasks to phases: tokenization → lexical; structure recognition → syntax.Select the statement that mentions recognizing constructs and generating IR.Confirm other options describe lexical responsibilities (tables, tokens). Verification / Alternative check: Standard compiler pipelines show: Lexing → Parsing → Semantic analysis → IR → Optimization → Code generation. Parsing is where grammatical structure is enforced. Why Other Options Are Wrong: (b) and (c) correspond to symbol/literal table construction typically driven by the lexer and semantic phases; (d) describes lexical tokenization rather than parsing. Common Pitfalls: Conflating tokenization with parsing; assuming symbol tables are fully built before syntax checks (they evolve across phases). Final Answer: to recognize the major constructs of the language and to call the appropriate action routines that will generate the intermediate form or matrix for these constructs.

Question 20

File organizations – terminology for zero-based record addressing The file structure that redefines its first record at a base of zero is referred to as:

Accepted Answer

Introduction / Context: Data files can be organized in various ways. Relative (or direct) files address records by a relative number (RRN), enabling direct access via arithmetic on record numbers rather than by scanning sequential keys. Given Data / Assumptions: Records are addressed by a relative record number. The base may be conceptualized as zero (or one) depending on the system. The question emphasizes zero-based indexing semantics. Concept / Approach: Relative organization maps each record to a slot indexed by a relative number. Whether the first record is numbered 0 or 1 is an implementation detail; the defining feature is positional addressing rather than key comparisons. Hashing uses a hash function to compute an address from a key—related to direct access but different in terminology and mechanism. “Key fielding” and “dynamic reallocation” are not standard names for this structure. Step-by-Step Solution: Identify structure using numeric slot addressing → relative (RRDS-style) files.Note zero-based indexing aligns naturally with relative addressing.Choose “relative organization.” Verification / Alternative check: In VSAM RRDS or other relative file systems, applications reference records by RRN; some environments start at 0, others at 1, but the organization remains “relative.” Why Other Options Are Wrong: Hashing derives addresses from keys; it is not just zero-based numbering. “Key fielding” and “dynamic reallocation” are not canonical terms for file organizations. Common Pitfalls: Equating hashing with relative addressing; assuming sequential access when the defining feature is direct indexing. Final Answer: relative organization.

Operating Systems Concepts Questions