How Operating Systems Work

• A. To compile high-level programming languages into machine code
• B. To manage hardware resources and provide a common environment for application programs
• C. To design the physical layout of computer chips
• D. To connect computers to the internet without a network card

• A. The graphical user interface that users interact with
• B. A collection of installed application programs
• C. The core component that directly controls hardware and manages system resources
• D. The keyboard driver used during system startup

• A. So that programs can be written without needing to know the specific details of each hardware device
• B. So that the hardware runs at a slower and safer speed
• C. So that users are prevented from installing any new software
• D. So that the CPU can be replaced without changing the motherboard

• A. To allow user programs to request services from the operating system kernel in a controlled way
• B. To permanently store files on the hard disk
• C. To display error messages on the monitor
• D. To turn the computer on and off automatically

• A. Printing each program's output on separate pages
• B. Sharing the CPU and memory among the programs so they do not interfere with each other
• C. Installing a separate processor for each program
• D. Deleting programs that have been running too long without user input

• A. A program stored on disk that has not been executed yet
• B. An running instance of a program with its own memory space and resources ✓
• C. A hardware device that manages input and output
• D. A single instruction executed by the CPU

Why: A process is a program in execution. It has its own address space, registers, and resources, which distinguishes it from a program sitting on disk as a static file.

• A. An independent process with its own separate memory
• B. A lightweight unit of execution within a process that shares the process's memory ✓
• C. A type of file stored in the operating system kernel
• D. A hardware interrupt signal sent to the CPU

Why: Threads are lightweight execution units inside a process. Threads within the same process share its code, data, and heap, but each has its own stack and program counter.

• A. Only the process's source code
• B. Information the OS needs to manage a process, such as its state, registers, and memory information ✓
• C. The user's login password
• D. A copy of the entire hard drive

Why: The PCB is a data structure the kernel uses to track each process, holding its state, program counter, CPU registers, scheduling information, and memory management details.

• A. Open, closed, and locked
• B. New, ready, running, waiting, and terminated ✓
• C. Read, write, and execute
• D. Active, inactive, and deleted

Why: The classic process lifecycle includes new (being created), ready (waiting for CPU), running (executing), waiting (blocked on an event such as I/O), and terminated (finished).

• A. Processes share memory while threads do not
• B. Threads share memory within their process, while separate processes have isolated memory ✓
• C. Neither processes nor threads use memory
• D. Threads always use more memory than processes

Why: Each process has its own isolated address space, whereas threads within the same process share that address space. This sharing makes thread communication faster but requires synchronization to avoid conflicts.

• A. To allocate memory to running processes
• B. To decide which ready process gets the CPU next so the CPU is used efficiently ✓
• C. To manage files on the disk
• D. To control network communication between devices

Why: CPU scheduling determines which process in the ready queue is given the CPU next, aiming to keep the CPU busy and improve system performance and responsiveness.

• A. Shortest Job First (SJF)
• B. Round Robin
• C. First-Come, First-Served (FCFS) ✓
• D. Priority Scheduling

Why: First-Come, First-Served (FCFS) is a non-preemptive algorithm that runs processes in arrival order, like a queue at a checkout counter.

• A. The total time a process needs to complete
• B. The fixed amount of CPU time each process receives before being preempted ✓
• C. The time spent waiting for input/output
• D. The time required for a context switch

Why: In Round Robin, each process gets the CPU for a fixed time slice called the time quantum. If it doesn't finish, it goes to the back of the ready queue.

• A. Moving a process from disk to memory
• B. Saving the state of one process and loading the state of another so the CPU can switch between them ✓
• C. Changing the priority of a process permanently
• D. Transferring data between two hard drives

Why: A context switch saves the current process's registers and state, then restores the saved state of the next process, allowing multitasking. It carries overhead, so it should be minimized.

• A. Deadlock
• B. Starvation ✓
• C. Thrashing
• D. Fragmentation

Why: Starvation occurs when a low-priority process waits indefinitely because higher-priority processes keep arriving. Aging, which gradually raises a waiting process's priority, is a common solution.

• A. To increase the clock speed of the CPU
• B. To allocate and track how memory is used by processes ✓
• C. To manage network connections between computers
• D. To control which users can log into the system

Why: Memory management allocates memory to processes, keeps track of which parts are in use, and frees memory when it is no longer needed, so that multiple programs can run safely and efficiently.

• A. A physical location on the hard disk
• B. An address generated by a program that is translated to a physical address by the system ✓
• C. The IP address assigned to a computer on a network
• D. A memory address that cannot be accessed by any process

Why: Programs use virtual addresses, which the operating system and hardware translate into real physical RAM locations. This lets each process believe it has its own private address space.

• A. Printing documents stored in memory
• B. Dividing memory into fixed-size blocks called pages to simplify allocation ✓
• C. Storing user passwords in memory
• D. Sending memory contents over a network

Why: Paging divides both virtual memory and physical memory into fixed-size blocks, called pages and frames. This removes the need for contiguous allocation and reduces fragmentation.

• A. An error in a printed page of a document
• B. A hardware failure that destroys RAM
• C. An event that occurs when a program accesses a page not currently loaded in physical memory ✓
• D. A bug in the operating system kernel that crashes the computer

Why: A page fault happens when the requested page is not in RAM. The OS then loads the page from disk into memory and resumes the program, which is a normal part of virtual memory operation.

• A. Splitting a file into smaller parts for backup
• B. Wasted memory that becomes unusable because free space is broken into scattered pieces ✓
• C. Dividing a program into multiple threads
• D. Encrypting memory to protect it from attackers

Why: Fragmentation wastes memory because free space is split into small scattered gaps that may be too small to satisfy new requests, even when enough total free memory exists.

• A. To execute programs faster by increasing CPU clock speed
• B. To organize and manage how data is stored, named, and retrieved on storage devices ✓
• C. To manage network connections between computers
• D. To allocate memory to running processes

Why: A file system provides a structured way to store, name, locate, and retrieve data on storage devices. Memory allocation is handled by the memory manager, and network connections by networking subsystems.

• A. Register
• B. Cache
• C. File
• D. Kernel

• A. A special type of file that stores executable code only
• B. A container that holds references to files and other directories, organizing them hierarchically
• C. A temporary storage area that is erased on reboot
• D. A hardware device that reads data from disks

• A. Blocks make files impossible to fragment
• B. Storage devices read and write data efficiently in fixed-size chunks, and blocks simplify allocation and management
• C. Blocks encrypt data automatically
• D. Individual bytes cannot be stored on any physical medium

• A. The amount of disk space a file is allowed to occupy
• B. The speed at which a file can be read from disk
• C. Rules that define which users or processes can read, write, or execute a file
• D. The maximum size a file may grow to

• A. To replace the CPU scheduler with a faster algorithm
• B. To translate generic OS requests into device-specific commands ✓
• C. To store user files on the hard disk
• D. To encrypt all data sent over the network

Why: A device driver acts as an intermediary between the operating system and a hardware device. It converts the OS's generic input/output requests into the specific commands and signals that the particular device understands.

• A. Context switch
• B. Page fault
• C. Interrupt ✓
• D. Deadlock

Why: An interrupt is a signal from a device (such as a keyboard or disk controller) that tells the CPU an event needs attention. The CPU pauses its current work, handles the interrupt, and then resumes.

• A. Character devices are always faster than block devices
• B. Character devices transfer data one byte or character at a time, while block devices transfer data in fixed-size blocks ✓
• C. Block devices cannot be read from, only written to
• D. Character devices are only used for storage

Why: Character devices, such as keyboards and serial ports, handle data as a stream of individual characters. Block devices, such as hard drives and SSDs, read and write data in fixed-size blocks, which allows random access.

• A. To permanently store user passwords
• B. To encrypt data before it reaches the device
• C. To temporarily hold data so that speed differences between devices and the CPU do not cause delays or data loss ✓
• D. To prevent any device from being connected at the same time

Why: Devices and the CPU operate at very different speeds. A buffer is a temporary memory area that holds data while it is being transferred, allowing the faster component to continue working without waiting for the slower one.

• A. A method where the CPU repeatedly checks a device's status to see if it needs service ✓
• B. A method where the device sends a survey to the user
• C. A method for deleting unused device drivers
• D. A method for dividing memory into equal pages

Why: In polling, the CPU continuously checks a device's status register to determine whether it is ready. This is simple but wastes CPU time, which is why interrupts are often preferred for efficiency.

• A. To make the computer run faster
• B. To separate each user's files, settings, and permissions from others ✓
• C. To reduce the amount of storage the system needs
• D. To allow the hardware to be replaced without reinstalling software

Why: User accounts provide isolation so that each user's data and settings are kept separate and access is controlled by permissions.

• A. Users should have the fewest possible files on their computer
• B. Every process and user should have only the permissions needed to perform its task ✓
• C. Only the administrator should be allowed to log in
• D. Programs should run with the highest available system access

Why: Least privilege limits each user or program to the minimum access required, reducing damage if something goes wrong or is compromised.

• A. To make programs load more quickly from disk
• B. To prevent ordinary applications from directly modifying critical system code and hardware ✓
• C. To allow multiple monitors to be used at once
• D. To compress memory automatically

Why: Kernel mode has full hardware access, so restricting user programs to user mode protects the system from crashes and malicious changes.

• A. To control which users or groups can perform specific actions on a file ✓
• B. To automatically back up files to another drive
• C. To compress files so they take up less space
• D. To encrypt files so they cannot be copied over a network

Why: File permissions define which users or groups may read, modify, or run a file, enforcing access control on stored data.

• A. All programs share the same memory space for faster communication
• B. Each process is given its own protected memory space that other processes cannot freely access ✓
• C. Processes are stored on a separate physical computer
• D. Only one process can run on the system at a time

Why: Process isolation gives each running program its own protected address space, so one faulty or malicious program cannot read or corrupt another's memory.