Question 1

Process Relationships  A relationship between processes in which each has a section of code that must not execute while another process is executing its own such section is called what?

Accepted Answer

Introduction / Context: When processes or threads share resources, they must coordinate access to avoid inconsistent states. The core requirement is that critical sections do not overlap, a property known as mutual exclusion (often shortened to “mutex”). Given Data / Assumptions: Processes have critical sections that access shared state. We seek the name of the required relationship/condition between them. Concept / Approach: Mutual exclusion is the property that only one process at a time can be in its critical section with respect to a particular resource. It is enforced using mechanisms like locks, semaphores, monitors, or atomic instructions. Step-by-Step Solution: Identify the critical regions in each process.Apply a synchronization primitive to ensure no overlap in those regions.Verify that interleavings cannot cause races or inconsistencies. Verification / Alternative check: Testing under load should show that only one thread enters the critical region at a time for the protected resource and data remains consistent. Why Other Options Are Wrong: Semaphores (Option A) are one technique to implement mutual exclusion, not the relationship itself.Multiprogramming/Multitasking (Options C/D) describe general execution modes, not the exclusivity requirement. Common Pitfalls: Using coarse-grained locks that hurt performance. Forgetting to guard all accesses to the resource, leading to residual races. Final Answer: Mutual exclusion.

Question 2

Linking fundamentals in systems programming: Object modules produced by an assembler may contain unresolved external references (symbols defined in other modules). Which program combines two or more such object files and resolves these externals to …

Accepted Answer

Introduction / Context: When software is built, source code is translated into object modules that may reference functions or data defined elsewhere. Understanding which tool resolves these unresolved external references is central to build systems, portability, and modular program design. Given Data / Assumptions: Multiple object modules exist after assembly/compilation. Some symbols are undefined in one module but defined in another. The goal is to create a runnable image or library with all references resolved. Concept / Approach: The linker reads object modules and libraries, matches undefined symbols to their definitions, performs relocation, lays out sections, and emits an executable or library. The loader places this finished image into memory at run time. The operating system provides system services, and the compiler/assembler generate object code but do not finish multi-module symbol resolution by themselves. Step-by-Step Solution: Identify the phase where cross-module symbols are matched: linking.Recognize relocation: the linker adjusts addresses based on final layout.Differentiate roles: compiler/assembler produce objects; loader loads; OS manages execution.Therefore, the correct program is the linker. Verification / Alternative check: Typical toolchains (e.g., gcc/clang + ld, MSVC + LINK) explicitly invoke a linker step that accepts multiple .o/.obj files and libraries to produce .exe, .out, or .dll/.so outputs. Why Other Options Are Wrong: Operating system: provides services; it does not resolve build-time externals. Loader: maps an already linked image into memory. Compiler: translates high-level code to objects but leaves unresolved references. None: incorrect because a linker exists for this function. Common Pitfalls: Confusing the loader with the linker; assuming the compiler alone creates executables; overlooking the relocation step performed at link time. Final Answer: linker

Question 3

Role of the operating system: The OS acts as a software interface between the user and which underlying layer of the computer system?

Accepted Answer

Introduction / Context: The operating system (OS) is the foundational software layer that manages resources and presents a convenient interface to users and applications. Knowing what it sits on top of clarifies how programs interact with devices securely and efficiently. Given Data / Assumptions: An OS mediates interactions between applications/users and the machine. Hardware includes CPU, memory controllers, storage, and I/O devices. Peripherals, memory, and the screen are components of the broader hardware layer. Concept / Approach: The OS abstracts hardware complexity via system calls, device drivers, file systems, and schedulers. While we often talk about memory or display specifically, these are subsets of hardware resources. Therefore, the OS serves as an interface between the user and the hardware as a whole, not only one device category. Step-by-Step Solution: Identify the OS’s responsibilities: process, memory, device, and file management.Note that all responsibilities require controlling hardware mechanisms.Determine the broadest accurate layer: hardware.Select “hardware” over narrower subcomponents like “screen.” Verification / Alternative check: System architecture diagrams consistently show: user → applications → operating system → hardware. Device drivers within the OS provide the uniform interface. Why Other Options Are Wrong: Peripheral, memory, screen: each is a subset; the OS interfaces with all hardware, not just one part. None: incorrect because OS-hardware mediation is a fundamental principle. Common Pitfalls: Equating the OS strictly with UI; ignoring headless or embedded systems where the OS still interfaces with hardware without a screen. Final Answer: hardware

Question 4

Graphical user interface elements in Microsoft Windows: Which items represent the core user-interface features commonly associated with Windows programs?

Accepted Answer

Introduction / Context: Microsoft Windows popularized the graphical user interface (GUI) for mainstream computing. Recognizing its signature elements helps users and developers align with common usability expectations and design patterns. Given Data / Assumptions: Typical Windows applications present content within resizable windows. Menus enable command discovery and organization. Icons provide visual metaphors for actions and objects. Concept / Approach: Core GUI affordances include windows (containers with title bars), pull-down menus (structured command hierarchies), icons (symbols on desktop, taskbar, toolbars), dialog boxes, and controls. The question lists three standard components; together they form the primary interaction surface of many Windows programs. Step-by-Step Solution: Evaluate each option as a recognized GUI element.Confirm that Windows, menus, and icons are all fundamental to the Windows look-and-feel.When multiple correct elements are listed, choose the aggregate answer.Therefore, select “All of the above.” Verification / Alternative check: Microsoft UX guidelines and classic Windows applications (e.g., Notepad, Explorer) clearly feature windows, menus, and icons. Why Other Options Are Wrong: Picking a single element omits other equally essential components. “None” contradicts established UI conventions. Common Pitfalls: Confusing “Windows” the OS with the window widget itself; overlooking that modern ribbon UIs still rely on the same core elements and iconography. Final Answer: All of the above

Question 5

Network security concepts: Compared to end-to-end encryption, how secure is link encryption in typical multi-hop networks?

Accepted Answer

Introduction / Context: Encryption can be applied on individual links (hop-by-hop) or end-to-end between communicating endpoints. Understanding the implications of where decryption occurs clarifies the threat model and the confidentiality guarantees provided to users. Given Data / Assumptions: Multi-hop path with intermediate routers/switches. Link encryption encrypts traffic on each physical/logical link separately. End-to-end encryption protects payloads from sender to receiver. Concept / Approach: With link encryption, data are decrypted and re-encrypted at each intermediate device. Any compromised intermediate node can access plaintext, so confidentiality depends on every hop. End-to-end encryption keeps data encrypted across the entire path; only endpoints hold keys, so intermediates cannot read content. Therefore, link encryption provides weaker confidentiality than end-to-end in most scenarios. Step-by-Step Solution: Define link encryption: encrypt per link; decrypt at each hop.Define end-to-end: single cryptographic protection from sender to receiver.Compare exposure: intermediates see plaintext under link encryption but not under end-to-end.Conclude: link encryption is less secure regarding content confidentiality. Verification / Alternative check: Standards and best practices (e.g., TLS over the internet) endorse end-to-end to prevent intermediary snooping; VPNs may combine both for layered defense. Why Other Options Are Wrong: More secure: incorrect due to hop exposure. Cannot be used publicly: false; link encryption is common on ISP backbones. Used only to debug: false; it is a security technique, not a diagnostic tool. None: incorrect because “less secure” is accurate. Common Pitfalls: Assuming encryption anywhere guarantees full privacy; ignoring trusted middleboxes that terminate link encryption. Final Answer: is less secure than end-to-end encryption

Question 6

I/O control methods: In data communications, what does the term “polling” mean when a host interacts with multiple terminals or devices?

Accepted Answer

Introduction / Context: Polling is a classic method of device servicing where a controller queries each attached device in turn to determine whether it needs attention. This is common in legacy multi-drop lines and simple embedded systems without sophisticated interrupt mechanisms. Given Data / Assumptions: Multiple terminals or peripherals share a communication channel. The controller can either poll or use interrupts. We are interested in the definition of polling, not its performance trade-offs. Concept / Approach: Polling is an inquiry cycle. The master sequentially asks each slave device if it has data or a request pending. If a device responds affirmatively, the master services it; otherwise, it moves on. This contrasts with interrupts, where devices signal the host asynchronously. Step-by-Step Solution: Define the master–slave relationship on a shared medium.Describe the loop: master sends “Are you ready?” frames to each terminal.Service any terminal that indicates pending work.Repeat continuously or at set intervals. Verification / Alternative check: Protocols like HDLC derivatives and simple bus systems include polling modes where the primary station queries secondary stations. Why Other Options Are Wrong: Error detection/correction: handled by CRCs and ARQ, not polling. Multiplexing and memory updates: describes data handling, not the inquiry mechanism. Decision analysis: unrelated to device service inquiry. Common Pitfalls: Confusing polling with interrupt-driven I/O; assuming polling inherently corrects errors. Final Answer: inquires to see if a terminal has any transaction to send

Question 7

Language translation tools: Which of the following may be used to convert high-level language instructions into machine-executable form?

Accepted Answer

Introduction / Context: High-level source code must ultimately become machine-executable. Two primary approaches exist: compilation and interpretation. Knowing the tool that performs direct execution by translating on the fly is key to understanding runtime behavior and performance trade-offs. Given Data / Assumptions: We focus on converting high-level statements into actions a CPU can execute. “Interpreter” refers to a program that reads and executes source statements directly or after minimal translation. System software is a broad category that includes interpreters and compilers, but the question seeks a specific tool. Concept / Approach: An interpreter parses and executes the program statement-by-statement, often translating to intermediate steps at runtime. A compiler translates ahead-of-time into object/machine code. “Applications software” uses translators but is not itself a translator; an “operating environment” (like a GUI shell) does not perform language translation. Step-by-Step Solution: Identify translator types: compiler vs. interpreter.Map the prompt to a specific tool capable of executing code without separate build outputs.Select “an interpreter” as a valid converter of high-level instructions into actions.Reject vague or umbrella terms that are not specific tools. Verification / Alternative check: Languages such as Python and JavaScript are commonly interpreted; REPL environments exemplify line-by-line translation and execution. Why Other Options Are Wrong: System software: too broad and non-specific. Applications software: consumes translators; does not translate. Operating environment: provides runtime UI, not translation. None: incorrect because interpreters exist. Common Pitfalls: Assuming only compilers perform translation; ignoring hybrid JIT approaches that still qualify as interpretation at runtime. Final Answer: an interpreter

Question 8

Interpreter characteristics: Which statement is NOT true about an interpreter when compared with a compiler?

Accepted Answer

Introduction / Context: Programming language translators come in two classic forms: compilers and interpreters. Distinguishing their behaviors helps developers anticipate performance, deployment, and debugging workflows. Given Data / Assumptions: An interpreter executes source statements directly or via a transient internal form. A compiler emits a separate object or executable file before execution. We seek the statement that is not true for interpreters. Concept / Approach: Interpreters are translators that process statements at runtime. They typically do not produce standalone object modules. Instead, they analyze (parse) and execute each statement when needed, often re-analyzing on each run unless caching is used. Therefore, the claim that an interpreter “generates an object program” is false for a pure interpreter. Step-by-Step Solution: List interpreter features: immediate execution; no permanent object file.Compare with compiler features: ahead-of-time object/executable generation.Identify the mismatched statement: generating an object program.Select option that is therefore not true for interpreters. Verification / Alternative check: Language docs (e.g., Python, Ruby) confirm that typical workflows run source directly via an interpreter; compiled languages (C/C++) produce .o/.obj files then link. Why Other Options Are Wrong: Interpreter is a translator: true. Analyzes each statement for execution: characterization of interpretation. All of the above: cannot be true because option A is false. Common Pitfalls: Confusing bytecode-producing interpreters with compilers; even then, a separate linkable object program is not typically produced. Final Answer: Interpreter generates an object program from the source program

Question 9

Compiler tables and definitions: In the context of a language processor, what is a Terminal Table typically defined as?

Accepted Answer

Introduction / Context: Language translators use several auxiliary tables to manage symbols and grammar elements. Knowing the purpose of each—terminal, identifier, and literal tables—clarifies how compilers parse and analyze source code. Given Data / Assumptions: “Terminals” are the basic symbols of the grammar: keywords, operators, and punctuation. Lexical analysis classifies input into tokens. Permanent tables differ from per-program symbol or literal tables. Concept / Approach: The Terminal Table is a permanent catalog of the language’s terminal symbols—keywords and special symbols—typically fixed for a language definition. In contrast, a Literal Table stores constants encountered in a program, and an Identifier Table lists user-defined names. Parsing tables (decision tables) are separate automaton artifacts used during syntax analysis. Step-by-Step Solution: Identify what belongs in a permanent, language-wide list: keywords and special symbols.Exclude program-specific entities (identifiers, literals).Exclude parser decision structures that are not “terminal tables.”Select the definition that matches: a permanent table listing keywords and special symbols. Verification / Alternative check: Compiler design texts separate terminal/identifier/literal tables clearly; lexer uses the terminal table to recognize keywords and operators. Why Other Options Are Wrong: Constants only: describes a literal table. Decision rules/patterns: describes parsing tables, not terminals. Token list as they appear: describes a token stream or symbol table for a specific program. Common Pitfalls: Confusing the general language dictionary (terminals) with a program’s symbol inventory (identifiers and literals). Final Answer: a permanent table which lists all key words and special symbols of the language in symbolic form.

Question 10

Defining an operating system: What does the term “operating system” most accurately refer to?

Accepted Answer

Introduction / Context: An operating system (OS) is the core software layer that governs computer operation. Properly defining it helps distinguish it from compilers, applications, and hardware control specifics. Given Data / Assumptions: OS responsibilities include process, memory, file, device, and security management. It is a software suite, not a single program. It is distinct from user behavior and from language translation tools. Concept / Approach: The OS coordinates the execution of programs and the use of hardware resources. It provides abstractions (files, processes, sockets) and enforces policies (scheduling, protection). Other tasks—such as compiling high-level languages—are separate tools that may run within the OS but are not the OS itself. Step-by-Step Solution: List OS domains: CPU scheduling, memory management, I/O, storage, networking.Differentiate from compilation (a development tool).Differentiate from device-specific operation (e.g., a single drive’s firmware).Choose the option describing a set of control programs. Verification / Alternative check: Standard textbooks define an OS as system software that manages computer hardware and software resources and provides common services for programs. Why Other Options Are Wrong: Operator behavior: human process, not software. Language conversion: compiler function. Floppy drive operation: hardware/firmware behavior, not the OS as a whole. Common Pitfalls: Equating an OS solely with its graphical shell; ignoring command-line or embedded OSes with no GUI. Final Answer: a set of programs which controls computer working

Question 11

Minimum requirement to use a computer system: Which software component is essential to operate a computer and run application programs?

Accepted Answer

Introduction / Context: Before any application can run, the computer needs a manager to coordinate hardware and provide services. Identifying this essential layer clarifies why machines with no OS are limited to firmware diagnostics or single-purpose code. Given Data / Assumptions: General-purpose computing environment is intended (not a bare-metal embedded microcontroller scenario). Users wish to run applications, access files, and interact with devices. Translators like compilers and interpreters require an OS to execute in typical desktop/server contexts. Concept / Approach: The operating system is the indispensable system software that initializes the machine, manages resources, and provides APIs and system calls. Compilers and assemblers are development tools; they are not required for running already-built applications. An interpreter is also an application that itself runs under the OS. Step-by-Step Solution: Define “essential”: without the OS, the machine cannot schedule apps or manage devices broadly.Contrast with compilers/assemblers: useful for building software, not mandatory for everyday application use.Select the OS as the necessary component.Discard ambiguous or malformed alternatives. Verification / Alternative check: Boot sequences (BIOS/UEFI → bootloader → OS kernel) demonstrate the OS’s central role in transitioning to a multi-process, multi-user environment. Why Other Options Are Wrong: Compiler/Assembly: used by developers, not required to use the computer day-to-day. Interpreter of the above: ill-formed and not essential. None: incorrect since an OS is required. Common Pitfalls: Confusing development tools with runtime requirements; overlooking specialized embedded cases not implied by the question. Final Answer: Operating system

Question 12

Software distribution models — PC-Write example:  The powerful text editor PC-Write was distributed for general use with a small voluntary fee. Such programs are commonly referred to as what?

Accepted Answer

Introduction / Context: Many classic PC utilities, including editors like PC-Write, were distributed under a try-before-you-buy model. Understanding the naming and expectations of this model helps learners distinguish licensing from technical categories such as firmware or general software. Given Data / Assumptions: The example is a text editor widely shared in the early PC era. Users could try the full program and were encouraged to pay a modest registration fee. No hardware embedding or manufacturer lock-in is implied. Concept / Approach: The term shareware describes software distributed freely for evaluation with an expectation or request for payment if the user continues to use it. It contrasts with freeware (no payment requested), commercial boxed software (paid up front), and firmware (code stored in nonvolatile memory within hardware). Step-by-Step Solution: Identify the distribution model: try first, then pay a small fee.Match this model to the term shareware.Exclude firmware because it denotes embedded code on devices.Exclude generic software or playful terms like mindware that do not capture the model. Verification / Alternative check: Historical materials and magazine ads from the era labeled PC-Write and similar products as shareware, often including a registration address and suggested price. Why Other Options Are Wrong: Software: too broad; all programs are software. Firmware: hardware-embedded code, not a distribution model. Mindware: not an industry term here. None of the above: incorrect because shareware is the precise label. Common Pitfalls: Confusing shareware with freeware or open source. Shareware may be closed source but allows evaluation without immediate purchase. Final Answer: Shareware

Question 13

Multiprogramming performance effect:  Under multiprogramming, how does average turnaround time typically change for short jobs versus long jobs?

Accepted Answer

Introduction / Context: Multiprogramming allows multiple jobs to share the CPU by interleaving execution. This impacts turnaround time, which is the total time from job submission to completion. Understanding the tradeoffs for short versus long jobs is core to operating system scheduling concepts. Given Data / Assumptions: The system supports multiple jobs in memory at once. CPU and I O overlap is possible; when one job waits, another can run. Turnaround time includes waiting, running, and I O times. Concept / Approach: Short jobs benefit because they can grab small CPU quanta and complete sooner instead of waiting for a single long job to finish. Long jobs, however, face preemption and time slicing that can slightly extend their turnaround time compared to running alone because of context switching and competition for CPU. Step-by-Step Solution: Recognize that time slicing and overlapping I O reduce idle time for short jobs.Understand that long jobs yield CPU repeatedly, adding wait components.Therefore, short jobs tend to have shortened turnaround time, while long jobs are slightly lengthened.Select the option that states shortened for short jobs and lengthened for long jobs. Verification / Alternative check: Empirical studies of round-robin and multi level feedback queue policies show improved responsiveness for short and interactive tasks, often at a small cost to long CPU bound tasks, aligning with the selected option. Why Other Options Are Wrong: Lengthened; shortened or lengthened; lengthened contradict typical multiprogramming outcomes. Shortened; shortened assumes no overhead or competition effects on long jobs. None of the above is incorrect because one option matches standard behavior. Common Pitfalls: Equating throughput improvements with universal turnaround improvements; ignoring context switch overhead and queueing effects on large jobs. Final Answer: shortened; lengthened

Question 14

Job queues in operating systems:  Special system software that assembles incoming jobs and manages a queue for later processing is called what?

Accepted Answer

Introduction / Context: Batch and time sharing systems rely on components that accept work, queue it, and feed it to devices or subsystems when they are ready. This is crucial for printers, mail systems, and batch processing pipelines. Given Data / Assumptions: Jobs may arrive faster than a device can service them. An intermediate buffer or queue is needed. The OS or utility should manage ordering and access control. Concept / Approach: Spooling stands for Simultaneous Peripheral Operations On Line. A spooler collects output (or input) into a queue on disk and later feeds it to the target device, decoupling job submission from device availability. Examples include print spoolers and mail queue daemons. Step-by-Step Solution: Identify the function: create and manage a job queue.Associate that function with spooling and the spooler service.Exclude interpreter (executes source code) and linkage editor (links object modules).Choose spooler. Verification / Alternative check: Administrative tools such as print management utilities explicitly refer to the spooler that holds jobs before printing. Why Other Options Are Wrong: Drive: storage hardware, not queue management software. Interpreter: executes high level code, not queueing. Linkage editor: links objects into executables. None of the above is incorrect because spooler is correct. Common Pitfalls: Confusing a device driver with a spooler; a driver interfaces hardware, while a spooler manages queues and scheduling for that hardware. Final Answer: Spooler

Question 15

System security — most common control:  Among typical security methods, which is the most commonly used mechanism for basic system access control?

Accepted Answer

Introduction / Context: Information security uses many layers of defense. While encryption and firewalls protect data in transit and define network boundaries, everyday user access to systems is most commonly controlled by credentials such as usernames and passwords. Given Data / Assumptions: We focus on the most common method, not the strongest or most modern. User access typically begins with an authentication step. Enterprises may also use multifactor authentication, but passwords remain widespread. Concept / Approach: Passwords provide knowledge based authentication. They are ubiquitous across operating systems, applications, and network services. Although organizations should pair them with additional factors, in practice passwords remain the default first line of access control worldwide. Step-by-Step Solution: List common security tools: passwords, encryption, firewalls.Identify which is most commonly used directly by end users to gain access.Select passwords as the most common access control mechanism.Confirm that encryption and firewalls serve different primary purposes. Verification / Alternative check: System setup wizards, directory services, and login prompts consistently rely on password based credentials by default, evidencing their ubiquity. Why Other Options Are Wrong: Encryption: protects confidentiality and integrity but is not by itself an access gate for everyday logins. Firewall: enforces network policy at perimeters, not per user logins. All of the above: asks for the most common single method; passwords best fit. None of the above: incorrect because passwords are valid and common. Common Pitfalls: Equating most common with most secure. Best practice combines passwords with multifactor authentication and strong password policies. Final Answer: passwords

Question 16

Operating system residence:  While a computer is powered on, where must the operating system's kernel and essential components remain resident to manage processes and devices?

Accepted Answer

Introduction / Context: The kernel is the core of an operating system, handling CPU scheduling, memory management, and device control. For immediate responsiveness and hardware control, key parts of the OS must remain resident during operation. Given Data / Assumptions: Main storage refers to main memory (RAM). Disk drives and removable media are nonvolatile storage, slower and not directly executable by the CPU. We consider normal general purpose systems. Concept / Approach: After boot, the kernel and some drivers are loaded into RAM. The CPU executes instructions from memory, not directly from disks or floppies. Therefore, the OS core must stay in main storage while the system runs. Additional modules may be loaded on demand, but resident pieces remain in RAM to serve interrupts and system calls promptly. Step-by-Step Solution: Recall that instruction fetch occurs from memory.Recognize that servicing interrupts requires immediate, resident code.Conclude that main storage is required for OS residency during operation.Choose main storage accordingly. Verification / Alternative check: Kernel maps in RAM are visible in system tools, and system crashes result when critical kernel code cannot remain resident, confirming the need for RAM residency. Why Other Options Are Wrong: Floppy disk or disk drive: used for storage and paging, but CPU executes from RAM. Primary storage: sometimes used synonymously with main memory, but the item explicitly identifying main storage is the clearest correct choice given the options. None of the above: incorrect because main storage is right. Common Pitfalls: Confusing where programs are stored long term (disk) with where they execute (RAM). Assuming the entire OS must always be resident; only essential parts must be. Final Answer: main storage

Question 17

Compile-and-Go loading schemes — drawbacks:  Which of the following describes the disadvantages of a classic Compile and Go loading scheme in program development?

Accepted Answer

Introduction / Context: Early development environments often used Compile and Go schemes, where the assembler or compiler immediately produced in memory code and transferred control to it. While simple, this approach has notable drawbacks for larger or modular systems. Given Data / Assumptions: Assembler or compiler remains resident during translation. No separate loader or linker phases are used. Programs may be multi module and multi language. Concept / Approach: Since the translator occupies memory, less RAM is available for the object program, leading to waste. Without a separate object file and loader, the source must be retranslated each run, increasing time. Finally, modular and mixed language builds are hard without a proper link step, limiting maintainability. Step-by-Step Solution: Evaluate memory usage: translator occupies space, reducing object program space.Evaluate workflow: every execution requires recompilation or reassembly.Evaluate modularity: lack of linking complicates multi segment and mixed language systems.Conclude that all listed drawbacks apply. Verification / Alternative check: Modern toolchains separated compile, assemble, link, and load stages precisely to resolve these disadvantages, validating the analysis. Why Other Options Are Wrong: Each individual disadvantage is true, so selecting only one is incomplete. None of the above contradicts well known limitations of Compile and Go. Common Pitfalls: Assuming simplicity translates to efficiency at scale; not accounting for iterative development where recompilation costs add up. Final Answer: all of the above

Question 18

Virtual memory — basic definition and mechanism:  Which description best captures how virtual memory is commonly implemented in paged systems?

Accepted Answer

Introduction / Context: Virtual memory provides the illusion of a large, contiguous address space by mapping virtual addresses to physical memory frames and secondary storage. Paging is the most widespread implementation technique. Given Data / Assumptions: We consider standard paging based systems. Programs are divided into fixed size pages; RAM into frames. The MMU performs address translation at runtime. Concept / Approach: In paging, a process address space is split into pages. The OS maintains page tables that map virtual pages to physical frames or to disk locations when pages are not resident. This permits demand paging, protection, and efficient sharing of code segments, while decoupling the program's view from physical memory size. Step-by-Step Solution: Identify the definition that explicitly describes page and frame subdivision.Confirm this aligns with how virtual memory is implemented in practice.Exclude options that describe processor time or general address concepts without mechanism.Select the paging description. Verification / Alternative check: Operating system texts depict virtual memory with page tables, TLBs, and frames, verifying that subdivision into pages and frames is the canonical approach. Why Other Options Are Wrong: Addresses generated by a processor: describes virtual address space, not the mechanism of virtual memory management. Processor time allocation: scheduling, not memory. Multiple programs in separate areas: true for multiprogramming but does not define virtual memory. Common Pitfalls: Confusing virtual address space with the paging mechanism; mixing CPU scheduling terms with memory management. Final Answer: is a method of memory allocation by which the program is subdivided into equal portions, or pages and core is subdivided into equal portions or blocks.

Question 19

Compiler front end artifacts:  During lexical analysis, which table records every literal constant that appears in the source program?

Accepted Answer

Introduction / Context: Compilers break down source code through lexical analysis (tokenization), syntax analysis (parsing), and semantic analysis. Along the way they build tables of symbols to drive later stages of translation and optimization. Given Data / Assumptions: Literals are explicit constants such as numbers, strings, and character constants appearing in code. Identifiers are names of variables, functions, and types. The lexer categorizes input into tokens and may populate tables for reuse. Concept / Approach: A literal table stores each distinct literal constant, often with attributes such as type, value, and sometimes storage placement. This enables deduplication and consistent handling in later phases, including code generation where literals may be placed in constant pools or data segments. Step-by-Step Solution: Differentiate between identifiers and literals.Select the table specifically dedicated to literal constants.Exclude terminal table and reductions, which are parser related structures.Choose literal table. Verification / Alternative check: Compiler design references list symbol tables for identifiers and separate literal tables or constant pools for numeric and string constants. Why Other Options Are Wrong: Terminal table: grammar terminals in parsing, not literal constants per se. Identifier table: names and bindings, not raw constants. Reductions: steps in parsing, not a table. None of the above: incorrect because literal table is correct. Common Pitfalls: Assuming all tokens go into a single symbol table; in practice, compilers separate identifiers from literals for clarity and efficiency. Final Answer: Literal table

Question 20

Virtual memory in practice:  Which statement best reflects the status of virtual memory usage in contemporary, widely used operating systems?

Accepted Answer

Introduction / Context: Virtual memory underpins process isolation, protection, and flexible memory management. It is a foundational feature that enables multitasking, memory mapped files, and crash containment in modern systems. Given Data / Assumptions: Mainstream desktop, server, and mobile operating systems are considered. Hardware support such as MMUs and TLBs is available on common CPUs. Virtual memory provides address translation and protection. Concept / Approach: All major commercial operating systems including Windows, macOS, mainstream Linux distributions, Android, and iOS implement virtual memory. They rely on paging, protection bits, and page replacement policies to present each process with an isolated virtual address space and to overcommit physical memory safely. Step-by-Step Solution: Evaluate the options for generality and correctness.Recognize that virtual memory is complex, so simple to implement is inaccurate.Acknowledge universal adoption across major OS families.Select used in all major commercial operating systems. Verification / Alternative check: Official OS documentation and architecture guides describe page tables, swap files, and memory protection as standard features, confirming ubiquity. Why Other Options Are Wrong: Simple to implement: VM requires intricate hardware software cooperation. Less efficient in utilization of memory: VM improves effective utilization via demand paging and sharing; inefficiencies are workload dependent. Useful only when fast I O devices are not available: virtual memory depends on storage but is not limited by I O speed in definition. None of the above: incorrect because widespread use is true. Common Pitfalls: Confusing ease of use with ease of implementation; overlooking mobile OSes that also use full virtual memory mechanisms. Final Answer: used in all major commercial operating systems

Operating Systems Concepts Questions