Unit 3 PGTRB

__________ system call creates new process in Unix.

• fork

• fork new

• create

• create new

Answer explanation

In Unix-like operating systems, the fork system call is used to create a new process. The fork system call creates a copy of the calling process. After a successful fork, the child process and the parent process continue execution independently. The child process receives a return value of 0, while the parent process gets the process ID (PID) of the child process.

Other options like "fork new", "create", and "create new" are not valid Unix system calls for creating a process.

In Linux operating system environment _______ command is used to print a file.

• print

• lpr

• ptr

• pr.

Answer explanation

The lpr command in Linux is used to print a file. It sends the file content to the default printer or a specified printer.

Other options like "print", "ptr", and "pr" do not serve this purpose in Linux.

The pr command, on the other hand, is used for formatting text for printing, but it does not directly print a file.

Which of the following UNIX/Linux pipes will count the number of lines in all the files having .c and .h as their extension in the current working directory?

• cat *.ch | wc -l

• cat *.[c-h] | wc -l

• cat *.[ch] | ls -l

• cat *.[ch] | wc -l

Answer explanation

cat .[ch] | wc -l - This will correctly find all files with the .c and .h extensions in the current directory using the pattern .[ch], then it concatenates their content using cat and counts the total number of lines with wc -l. This is the correct approach to solve the problem.

An Address in main memory is called:

• Virtual address

• Memory address

• Logical address

• Physical address

Answer explanation

A physical address refers to an actual location in the computer's main memory (RAM) where data is stored. It is used by the hardware to access memory directly. This contrasts with a logical (or virtual) address, which is used by programs and must be mapped to a physical address by the operating system or memory management unit (MMU). The physical address is the real address where data resides in the memory hardware.

Consider a virtual page reference string 1, 2, 3, 2, 4, 2, 5, 2, 3, 4. Suppose LRU page replacement algorithm is implemented with 3 page frames in main memory. Then the number of page faults are.

• 5

• 7

• 9

• 10

Answer explanation

Correct answer - ii) 7

The Least Recently Used (LRU) page replacement algorithm replaces the page that has not been used for the longest time when a page fault occurs and a new page needs to be loaded into memory.

Let’s go step by step to track the page references and page faults:

• Initially, we have 3 empty frames: _ _ _

• Reference: 1 → Load page 1 → 1 _ _ (Page Fault)

• Reference: 2 → Load page 2 → 1 2 _ (Page Fault)

• Reference: 3 → Load page 3 → 1 2 3 (Page Fault)

• Reference: 2 → Page 2 is already in memory, no page fault → 1 2 3 (No Page Fault)

• Reference: 4 → Replace least recently used (page 1) → 4 2 3 (Page Fault)

• Reference: 2 → Page 2 is already in memory, no page fault → 4 2 3 (No Page Fault)

• Reference: 5 → Replace least recently used (page 3) → 4 2 5 (Page Fault)

• Reference: 2 → Page 2 is already in memory, no page fault → 4 2 5 (No Page Fault)

• Reference: 3 → Replace least recently used (page 4) → 3 2 5 (Page Fault)

• Reference: 4 → Replace least recently used (page 5) → 3 2 4 (Page Fault)

Thus, the total number of page faults is 7.

A document that specifies how many times and with what data the program must be run in order to thoroughly test it.

• addressing plan

• test plan

• validation plan

• verification plan

Answer explanation

Test plan is the A document that specifies how many times and with what data the program must be run in order to thoroughly test it. It comes under testing.

Which of the following is not a process state?

• Terminated

• Running

• Blocked

• Execution

Answer explanation

There is no blocked state in a process model. The different states are ready, running, executing, waiting and terminated.

Which of the following are not shared by the threads of the same process?

(a) Stack

(b) Registers

(c) Address Space

(d) Message Queue

• (a) and (d)

• (b) and (c)

• (a) and (b)

• (a), (b) and (c)

Answer explanation

In a multi-threaded environment, threads within the same process share certain resources, but they also have some of their own private resources:

• Stack: Each thread has its own stack, as the stack is used for storing local variables, function calls, and return addresses. Hence, the stack is not shared among threads.

• Registers: Each thread has its own set of registers, including the program counter (PC), which tracks the thread's execution. Registers are private to each thread and are not shared.

• Address Space: All threads in the same process share the same address space, meaning they can access the same global variables, heap, and memory.

• Message Queue: Message queues are generally used for communication between processes or threads. While message queues can be shared among threads, the term "message queue" in the context of the question may refer to a queue used for inter-process communication, which is not shared by threads within the same process.

If an operating system does not allow a child process to exist when the parent process has been terminated, this phenomenon is called as -

• Threading

• Cascading termination

• Zombie termination

• Process killing

Answer explanation

Cascading termination occurs when a parent process's termination results in the automatic termination of its child processes. If the parent process ends, the system ensures that all its child processes are terminated as well, avoiding orphan processes. This process ensures that resources are properly freed and that no child processes are left running independently when their parent has ended.

Which of the following is not an example of system software?

• Language Translator

• Utility Software

• Communication Software

• Word Processors

Answer explanation

A system software is responsible for controlling the operations of a computer system. Word Processor is an application software since it is specific to its purpose.