Operating Systems Previous Year Questions (page 3)

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With no other process competing, the CPU is idle and the process is dispatched as soon as it arrives, at time 5. It cannot start before it arrives (time 0 or 4).

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SCAN (elevator algorithm) moves the head in one direction serving requests all the way to the end of the disk, then reverses. LOOK reverses at the last request instead of the disk end.

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getpid() returns the process ID of the calling (current) process. The parent's PID is returned by getppid().

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Virtual memory uses part of secondary storage (disk) as an extension of RAM, so programs larger than physical memory can run, with pages swapped in and out as needed.

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Software Configuration Management identifies, controls, audits and reports changes made to software during development and after release.

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Virtual memory uses disk space as an extension of RAM, giving programs the illusion of a very large main memory.

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By default BASH shows $ as the prompt for a normal user; # is shown for the root user.

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C is false: a monolithic kernel keeps user and kernel services in the same address space. A microkernel keeps them in separate address spaces.

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Sequential models such as the waterfall model are the oldest paradigms. They follow a linear flow, which often does not match changing real-world requirements.

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IMAP servers listen on TCP port 143. Port 443 is HTTPS, 80 is HTTP and 20 is FTP data.

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A good OS should complete many jobs per unit time (high throughput) and finish each job quickly (low turnaround time).

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Knowledge refining adds value to collected knowledge by discovering relationships, abstracting and preparing it to be shared.

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Interpolation is estimating y = f(x) for an x that lies between the given values x₀ and xₙ. Estimating outside this range is extrapolation.

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Packing, loading and shipping the goods to the buyer are part of the delivery/fulfilment step of the e-commerce process.

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In doc* the * matches any characters, so rm doc* deletes all files whose names begin with 'doc'.

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An information system is a set of interrelated components (people, hardware, software, data, procedures) that collect, process, store and distribute information to support decision-making and control.

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Translating source code into machine code is the job of a compiler or interpreter. The OS provides program execution, resource management and inter-process communication.

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Burst time is the CPU time a process needs to complete its execution, not the time it takes to start. The other definitions are correct.

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A page fault occurs when a program refers to a page that is not currently in main memory. The OS then loads it from secondary storage.

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The CMOS memory that stores BIOS settings is kept powered by a small coin-cell battery on the motherboard. POST runs at power-on (not shutdown), and bootstrap code is in ROM.

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/usr holds user programs, libraries and documentation. Temporary files are kept in /tmp.

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target="_top" opens the link in the full body of the window and breaks out of all frames. _blank opens a new window, and _parent opens it in the parent frame.

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New files are created with 666 permissions, and the default umask 022 turns that into 644, which is rw-r--r--.

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C shell, Korn shell and Bourne shell are Unix/Linux shells. "Alpha cell" is not a shell.

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The RAD model's phases are business modelling, data modelling, process modelling, application generation, and testing and turnover. "Development modelling" is not one of them.

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Web surfing (browsing) is moving from one website to another on the internet.

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The CLR is the .NET run-time engine. It handles JIT compilation, memory management (garbage collection) and security between the application and the OS.

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Communication system calls include creating/deleting connections, sending/receiving messages and attaching or detaching remote devices. Request/release device is device management, allocate/free memory is process control, read/write/reposition is file management.

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The mutual exclusion condition requires at least one resource to be held in a non-sharable mode, so only one process can use it at a time.

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The volume control block (superblock) holds volume details such as the number of blocks in the partition, block size and free-block count. Boot information is in the boot control block; the unique identifier is in the FCB.

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The dispatcher gives control of the CPU to the process chosen by the short-term scheduler, doing the context switch and jump to user mode.

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Much e-waste from developed countries is shipped to developing countries such as India, where metals like copper, iron, silicon, nickel and gold are recovered in recycling.

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LRU is a stack algorithm and never suffers from Belady's anomaly. FIFO can give more page faults with more frames, so it does suffer from it.

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Unicode assigns a unique number (code point) to every character of every written language, regardless of platform, device or program.

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New: the process is being created (3). Running: instructions are being executed (2). Ready: waiting to be assigned to a processor (1). So I-3, II-2, III-1.

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Process control system calls include end/abort, load/execute, create/terminate process, get/set attributes, wait for time, wait/signal event and allocate/free memory.

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A 32-bit OS can address at most 2³² bytes = 4 GB of RAM, while a 64-bit OS can address far more.

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Process departmentalisation groups work by the manufacturing process. It suits products whose production steps differ widely.

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Square brackets [ ] match any one character from a set or range, such as [abc] or [0-9]. * matches any string, ? matches any one character and ; separates commands.

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A knowledge economy is one whose growth is driven mainly by creating, spreading and using knowledge.

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Coda, developed at Carnegie Mellon, is a distributed file system descended from the Andrew File System (AFS). It adds support for disconnected operation.

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end, abort, create (and terminate, wait) are process control system calls. They create, end and manage processes.

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All three are correct points from the scope of business economics: demand forecasting predicts future demand, high inventory ties up funds, and pricing decisions decide profit.

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Virtual memory uses disk space as a temporary extension of RAM. This lets programs larger than physical memory run, with pages swapped in and out as needed.

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fork() returns −1 if creating the child fails. It returns 0 in the child, and the child's PID in the parent.

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Virtual memory combines RAM with space on the hard disk (swap/page file). Data in use is kept in RAM, and the rest is paged out to disk.

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Only when a process moves from running to terminated (exit) does the OS reclaim all of its memory. In sleeping or ready states the process still exists and keeps its address space.

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Ext4 (fourth extended file system) has been the default file system in most Linux distributions since about 2008. It replaced Ext3 and supports larger files and volumes and journaling.

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The operating system is the program that acts as an interface between the user and the hardware, managing resources such as the CPU, memory and devices. The kernel is only its core part.

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In Linux, the rm command deletes files (rm file.txt). rmdir removes only empty directories, and 'delete' and 'rdir' are not standard Linux commands.