Paper 2 CS System Software & Operating System Part 4

“Consider the case where i = 10 & i = 11, n = 21 & k = 12
P10 requests R10 & R11
P11 requests R10 & R8
Hence P10 & P11 inorder in deadlock.
“

“Three programs and each requires 3 tapes.
We will allocate minimum two tapes to each program then total tapes are 6 and each program requires one more tape to complete its operation.
So, we will allocate one tape to one program and that program will complete its operation.
After completion of operation of one program, all tapes allocated to that program are free. So no need of the extra tape to complete action.
Minimum tapes required are=(3*2 tape units) + 1 tape unit = 7″

The process of entering data into a storage location is destructive of previous contents using memory management techniques. In paging we are using LRU for replacing existing data.

→ In the case of semiconductor based memory technology, we get speed but the increase in the integration of various devices the cost is high.

“→ When designer decides to get rid of virtual memory entirely then hardware support is no longer needed.
→ Because special hardware support needed only for virtual memory.
→ Virtual memory is an integral part of a modern computer architecture. Implementations usually require hardware support, typically in the form of a memory management unit built into the CPU.
→ While not necessary, emulators and virtual machines can employ hardware support to increase performance of their virtual memory implementations.
“

“There are 32(25) surfaces, each surface have 64(26) tracks and each surface have 512(29) sectors.
So, to identify each sector uniquely,
5+6+9 = 20-bits are needed.
“

“The Dirty bit in a PCB(process control block) is set if the page is modified after being loading into cache memory.
This bit helps in maintaining updated data in the hard disk.”

” ●In object module it includes names and locations of all external symbols defined in the object module.
● To link to external symbols it must know the location of external symbols.
● So object module won’t consists of absolute addresses of internal symbols , Option D is correct.
“

” ●A relative record file contains records ordered by their relative key, a record number that represents the location of the record relative to where the file begins.
● For example, the first record in a file has a relative record number of 1, the tenth record has a relative record number of 10, and so forth. The records can have fixed length or variable length.
“

”
● Long term monitor metrics, as the name indicates, are the metrics that are collected for a resource for a longer term monitoring perspective. They are useful for continuous ongoing monitoring of the managed system.
● Monitoring the performance of operating systems and processes is essential to debug processes and systems, effectively manage system resources, making system decisions, and evaluating and examining systems.”

“→Working set defines the amount of memory that a process requires in a given time interval.
→ It defines “the working set of information W(t,τ) of a process at time t to be the collection of information referenced by the process during the process time interval (t−τ,t)”.
→ Typically the units of information in question are considered to be memory pages. This is suggested to be an approximation of the set of pages that the process will access in the future (say during the next τ time units), and more specifically is suggested to be an indication of what pages ought to be kept in main memory to allow most progress to be made in the execution of that process.
“

“● A Unix shell is a command-line interpreter or shell that provides a command line user interface for Unix-like operating systems.
● The shell is both an interactive command language and a scripting language, and is used by the operating system to control the execution of the system using shell scripts.
“

“● System software is a type of computer program that is designed to run a computer’s hardware and application programs.
● Real-time software enables the user to execute various task and activities all at the same time, as long as the programs are kept open.Real-time software refers to programs that can perform their assigned duties and functions right when they are assigned to run their given processes, not after the program has been executed, and not on a scheduled date
● Scientific software is defined by three characteristics: (1) it is developed to answer a scientific question; (2) it relies on the close involvement of an expert in its scientific domain; and (3) it provides data to be examined by the person who will answer that question.
● Business software or a business application is any software or set of computer programs used by business users to perform various business functions. These business applications are used to increase productivity, to measure productivity and to perform other business functions accurately.”

“● A boot loader is a type of program that loads and starts the boot time tasks and processes of an operating system or the computer system. It enables loading the operating system with in the computer memory when a computer is started or booted up.
● A boot loader is also known as a boot manager or bootstrap loader. Bootstrap loader is a program that resides in the computer’s EPROM, ROM, or other non-volatile memory. The bootstrap loader reads the hard drives boot sector to continue the process of loading the computer’s operating system. The term bootstrap comes from the old phrase “”Pull yourself up by your bootstraps.”””

fork system call is used to creates a new process in Unix.

A process residing in main memory and ready and waiting for execution, is kept on Ready queue.

“● Bélády’s anomaly is the phenomenon in which increasing the number of page frames results in an increase in the number of page faults for certain memory access patterns.
● This phenomenon is commonly experienced when using the first-in first-out (FIFO) page replacement algorithm.
● In FIFO, the page fault may or may not increase as the page frames increase, but in Optimal and stack-based algorithms like LRU, as the page frames increase the page fault decreases.
“

“● Remote Procedure Call (RPC) is a protocol that one program can use to request a service from a program located in another computer on a network without having to understand the network’s details.
● A procedure call is also sometimes known as a function call or a subroutine call.
● inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data.
● The RMI (Remote Method Invocation) is an API that provides a mechanism to create distributed application in java. The RMI allows an object to invoke methods on an object running in another JVM.
“

“Suppose N = Sum of all Needi,
A = Sum of all Allocation,
M = Sum of all Maxi.
Prove:
→ Assume this system is not deadlock free. If there exists a deadlock state, then A = m because there’s only one kind of resource and resources can be requested and released only one at a time.
→ From condition b, N + A = M < m + n. So we get N + m < m + n. So we get N < n. It shows that at least one process i that Needi = 0. From condition a, Pi can release at least 1 resource.
→ So there are n-1 processes sharing m resources now, condition a and b still hold. Go on the argument, no process will wait permanently, so there’s no deadlock.
“

“Semaphore are used to solve the problem of process synchronization and mutual exclusion.
Semaphore are 2 types.
Counting semaphore
Binary semaphore
“

“Given data, total 32 segments
Each segment size is 1K bytes.
Find the logical address=?
32 segments=25
Segment size=210
⇒ 25*210
⇒ 215
So, 15 bits are required.
“

“→ This type of scheduling is one of the very basic algorithms for Operating Systems in computers which can be implemented through circular queue data structure.
→ Round-robin (RR) is one of the algorithms employed by process and network schedulers in computing.
→ As the term is generally used, time slices (also known as time quanta) are assigned to each process in equal portions and in circular order, handling all processes without priority (also known as cyclic executive).
→ Round-robin scheduling is simple, easy to implement, and starvation-free.
→ Round-robin scheduling can also be applied to other scheduling problems, such as data packet scheduling in computer networks.
“

“Counting semaphore value is 7
After 20 P operations value of semaphore = 7 – 20 = -13
After 15 V operations value of semaphore = -13 + 15 = 2
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“→ When page frames increases, then no. of page faults decreases.
→ Such as if RAM size increases, then no. of page entries increases, then no. of page faults decreases.
“

“The no. of child process created = (2^n) -1
= (2^3) -1
= 7
(where n is number of fork() statements)
“

“→ Long term scheduler controls the degree of multiprogramming.
→ Ready queue of the processes resides in main memory.
→ A process can have multiple sub processes.
→ Multiple process of a single program cannot exist because each program can have only one process.
“

→ The dirty bit allows for a performance optimization i.e., Dirty bit for a page in a page table helps to avoid unnecessary writes on a paging device.