Operating Systems Previous Year Questions

Explanation

0 is the identifier for a program to inform the operating system (OS) about proper running of a program. Each of the non-zero value signifies unique error doing running of a program.

Explanation

Key Process Area (KPA) used in CMM identifies a cluster of related activities that, when performed collectively, achieve a set of goals considered important.

Explanation

New processes arrive at 5 per minute, i.e. one process every 60/5 = 12 seconds. Each process needs 6 seconds of service time. CPU utilization = (total service time required / total available time) × 100 = (6/12) × 100 = 50%. Hence the right option is (b).

Explanation

The design of virtual memory assumes that the underlying hardware supports virtual to physical mapping.

Explanation

$? : exit status of the last command executed. $# : number of arguments supplied to a script. $0 : file name of the current script. $* : all the arguments (list of arguments). So A-iv, B-iii, C-i, D-ii, i.e. option (c).

Explanation

In Linux the seq command prints a sequence of numbers from FIRST to LAST in steps of INCREMENT: seq FIRST INCREMENT LAST. If FIRST or INCREMENT is omitted, it defaults to 1. Here FIRST = 1, INCREMENT = 2 and LAST = 10, so the output is 1 3 5 7 9 (each number on its own line). Hence the answer is (c).

Explanation

Win·txt is a group of classes that is use for windows programming.

Explanation

CMM (Capability maturity model)– It is framework that describes an evolutionary improvement path for software organizations from an immature process to a mature, discipline one. The software process is at CMM level 5, if there is continuous process improvement, if there is quantitative feedback from the process and from piloting innovative ideas and technologies. Software processes are the CMM level 5, if there are process change management, detect prevention and technology change management, So software product engineering in not a key process area in CMM level 5

Explanation

Software testing is a process of executing a program or application with the intent of finding errors (the software bugs) and the main objective of software testing is to find any bug present in the software program. Besides, through the process of testing. One can determine the strengths and weaknesses of the program in other criteria such as path testing, dependency testing etc.

Explanation

Two-level scheduling is used to schedule efficiently when some processes are swapped out. A lower-level scheduler (e.g. round robin) selects only among the processes in memory, while a higher-level scheduler swaps processes in and out of memory. Hence I and III are correct.

Explanation

The umbrella activities in a software development life cycle process include the following: software project management, formal technical reviews, software quality assurance and software configuration management. Umbrella activities occur throughout the software process and focus primarily on project management, tracking and control.

Explanation

These process areas belong to maturity level 3 (Defined), which includes Requirements Development, Organizational Process Focus (OPF), Organizational Training (OT), Integrated Project Management (IPM) and Risk Management (RSKM).

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Software architecture is the set of significant decisions about the organization of a software system: the structural elements and their interfaces, their behaviour and collaboration, and their composition into larger subsystems.

Explanation

A computer based information system is needed because of the growing size of organizations which need to process large volumes of data, and such data must support timely and accurate decisions. So III and IV are true.

Explanation

In increasing order of access speed: Magnetic tapes < Optical disks < Magnetic (hard) disks < Electronic disks (flash/SSD) < Main memory < Cache < Registers.

Explanation

Windows Vista's built-in disk management (Logical Disk Manager) supports shrinking and expanding volumes.

Explanation

The waterfall model was first process model to be introduce. • It is also referred as linear sequential life cycle model • It is very simple to understand and use. In this each phase must be complicated fully before the next phase can begin. • In this model the testing stands only after the development is complete • In this model phases do not overlap

Explanation

Processes are not permanently assigned to a queue they can vary between queues as their priorities change

Explanation

Memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passing through itself, primarily performing the translation of virtual memory addresses to physical addresses. It is usually implemented as part of the central processing unit (CPU), but it also can be in the form of a separate integrated circuit. So we can say it is a chip to map virtual address to physical address

Explanation

Wow 32 is a running environment used in windows to run 16 bit windows application on a 32 bit machine

Explanation

You can edit more than one file at a time with vi. vi file1 file2 vi two (or more) files at the same time.

Explanation

A Unix file may be of any of the type like regular file, directory file, or device file.

Explanation

Refinement is surly a top down approach as we are extracting a particular type like person entity to s/w engineer. Refinement, process of elaboration, start with the statement of function defined at the abstract level, decompose the statement function in a step wise fashion until programming language statements are reached.

Explanation

The gettydefs file supplies the getty command with information about various terminal attributes, such as the default initialization and the login message. (i) There is nothing like contrab in Unix. (ii) The inittab file controls what happens whenever a Unix system is rebooted or forced to change run levels. (iii) init (short for initialization) is the first process started during booting of the computer system.

Explanation

Prototyping and iterative are well-known software process models. In the timeboxing model, development is done iteratively as in the iterative enhancement model, with each iteration done in a timebox of fixed duration. Glass boxing is a software testing approach, not a process model.

Explanation

In an OS, an indivisible (atomic) operation is performed entirely or not performed at all. This means the processor cannot be pre-empted during it.

Explanation

Windows 2000 uses the 16-bit UNICODE character set. Extended ASCII encodings are 8-bit or larger encodings that include the 7-bit ASCII characters.

Explanation

All three commands enable execute permission: X stands for execute and + adds the permission; ugo means user, group and others; a means all; with no class given, + applies it for all.

Explanation

rm chap* would remove all files beginning with chap. To remove a file whose name contains a special character, escape it with the backslash (\); this is called escaping or despecializing. So rm chap0\[1 – 3\] removes the file named chap0[1 – 3] itself.

Explanation

In the Unix file system, six types of file are distinguished: special, named pipes, links, symbolic links, regular (ordinary) and directory. A special file contains no data, but provides a mechanism to map physical devices to file names. The file names are used to access peripheral devices, such as terminals and printers.

Explanation

In image processing, blind deconvolution is a deconvolution technique that permits recovery of the target scene from a single or a set of blurred images in the presence of a poorly determined or unknown point spread function (PSF). It combines blur identification and image restoration.

Explanation

Application of stack(s) are: (i) Implementation of recursion. (ii) Evaluation of a postfix expression. (iii) Reverse a string. Job scheduling is commonly done via queue data structure.

Explanation

Given I/O requests: 98, 37, 14, 124, 65, 67, head at 32. Using FCFS scheduling, total disk moves = (98 – 32) + (98 – 37) + (37 – 14) + (124 – 14) + (124 – 65) + (67 – 65) = 66 + 61 + 23 + 110 + 59 + 2 = 321

Explanation

The scheduling algorithm works as round robin with time quantum T. After a process has executed for T units, its waiting time becomes least (lowest priority), and its turn comes again only after every other process has had a chance for T units.

Explanation

Remaining need = Max need – Current allocation: P₁ = 5, P₂ = 5, P₃ = 3, P₄ = 2. Total allocated = 10, so available = 12 – 10 = 2. Satisfy P₄ (need 2), it releases 3 → available 4. Satisfy P₃ (need 3), releases 5 → available 7 (after P₃ completes). Then P₁ and P₂ can be satisfied similarly. Hence the safe sequence is P₄, P₃, P₁, P₂.

Explanation

• Strategic value of data mining is time stamping → correct • Information collection is an expensive process in building an expert system → correct • An expert system is a computer system that emulates the decision making ability of a human expert.

Explanation

Evolutionary Model is an iterative and incremental approach to software development. It is preferred for software development when requirements are not clear.

Explanation

wc -l <a >b &: wc is the word count program, -l counts lines, <a takes input from a, >b writes output to b, and & runs the command in the background. So it counts the number of lines in a, writes the result to b, and does it in the background.

Explanation

The cron daemon is the standard tool for running commands on a pre-determined schedule. It starts when the system boots and runs as long as the system is up. Crontabs for individual users are stored under /var/spool/cron; there is one crontab file per user. So statement (d) is not correct.

Explanation

In UNIX, file access permissions are given as three octal digits: the first for the owner, the second for the group, the third for others. Each digit is rwx: 7 = rwx, 6 = rw-, 5 = r-x, 4 = r--, 3 = -wx, 2 = -w-, 1 = --x, 0 = none. 641 → owner can read and write, group members can read, others can execute only. 100 → owner can execute; all other access is prohibited. So both statements are correct.

Explanation

Zombie Process : The UNIX system assumes that if child process terminate, the parent collects some data about the child, As soon as this collection is made, the system releases information bits about the child process and removes its PID from the process table. The UNIX is forced to keep the child's Process ID (PID) and termination data in the process table indefinitely. Such a terminated process whose status is not collected called a zombie process.

Explanation

Parent and child share only the share memory segments everything else (like stack, heap etc) is duplicated.

Explanation

UNIX file system: Super block contains the number of i-nodes, the number of disk blocks, and the start of the list of free disk blocks.Correct An i-node contains accounting information as well as enough information to locate all the disk blocks that holds the file’s data.Correct All the files and directories are stored in data blocks.Correct Each i-node is 256-bytes long.Incorrect.It is 128 byte long.

Explanation

Association rule learning is a method for discovering intersecting relations between variables in large data base. It is intended to identify strong rules disconnected in database using some measures of interestingness.

Explanation

Converting 30 days into minutes, the fraction of time the system is not available = 10/(30 × 24 × 60) × 100 ≈ 0.023%. Availability = 100 – 0.023 ≈ 99.97%.

Explanation

Effective access time = 0.99 × (1 µsec + 0.008 × 2 µsec) + 0.002 × (10000 µsec + 1000 µsec) + 0.001 × (10000 µsec + 1000 µsec) ≈ (0.99 + 0.016 + 22.0 + 11.0) µsec ≈ 34.0 µsec.

Explanation

ls -l lists the files with details, grep "June" keeps the lines for files modified in June, and sort +10n skips ten fields and sorts the lines in numeric order. So the correct command is ls -l | grep "June" | sort +10n.

Explanation

A process's nice value (priority) can be set at the time of creation with the nice command, which takes a command line as an argument, and adjusted later with the renice command. So I, II and III are all true.

Explanation

Initial value S = 1. (1) P2 needs to access: S = 0 (no one waiting) (2) P1 needs to access: S = –1 (one process waiting) (3) P3 needs to access: S = –2 (two processes waiting) (4) P2 exits critical section: S = –1 (one process waiting) (5) P1 exits critical section: S = 0 (no process waiting)