04:14
jobsindia
1) State and explain about what an operating system is?
Operating system is made up of basically two functions they are managing resources and extending the machine. Operating system gives a user interface through which he can perform various functions. It acts as a medium for communication between the machine and user.
2) Explain about what a signal is?
A signal is a software mechanism that informs a process of the occurrence of asynchronous events. It does not employ priorities but it is more or less similar to a hardware interrupt. That is, all signals are treated equally. Signals that occur at the same time are presented to a process one at a time, with no particular ordering.
A signal is a software mechanism that informs a process of the occurrence of asynchronous events. It does not employ priorities but it is more or less similar to a hardware interrupt. That is, all signals are treated equally. Signals that occur at the same time are presented to a process one at a time, with no particular ordering.
3) What design and management issues are raised by the existence of concurrency?
The operating system must be able to keep track of the various active processes.
The operating system must allocate and de-allocate various resources for each active process.
The operating system must protect the data and physical resources of each process against unintended interference by other processes. This involves techniques that relate to memory, files, and I/O devices.
The results of a process must be independent of the speed at which the execution is carried out relative to the speed of other concurrent process.
The operating system must be able to keep track of the various active processes.
The operating system must allocate and de-allocate various resources for each active process.
The operating system must protect the data and physical resources of each process against unintended interference by other processes. This involves techniques that relate to memory, files, and I/O devices.
The results of a process must be independent of the speed at which the execution is carried out relative to the speed of other concurrent process.
4) What are the contexts in which concurrency may occur?
Concurrency may arise in three different contexts.
Multiple applications: -Processing time of the computer to be dynamically shared among a number of active jobs or applications
Structured application: - With principles of modular design and structured programming some applications can be effectively implemented as a set of concurrent process.
Operating system structure: -The same structuring advantages apply to the system programmer.
Concurrency may arise in three different contexts.
Multiple applications: -Processing time of the computer to be dynamically shared among a number of active jobs or applications
Structured application: - With principles of modular design and structured programming some applications can be effectively implemented as a set of concurrent process.
Operating system structure: -The same structuring advantages apply to the system programmer.
5) What is a data register and address register?
Data registers can be assigned to a variety of functions by the programmer. They can be used with any machine instruction that performs operations on data.
Address registers contain main memory addresses of data and instructions or they contain a portion of the address that is used in the calculation of the complete addresses.
Data registers can be assigned to a variety of functions by the programmer. They can be used with any machine instruction that performs operations on data.
Address registers contain main memory addresses of data and instructions or they contain a portion of the address that is used in the calculation of the complete addresses.
6) What are server operating systems?
These run on servers, which are very large personal computers, work stations, or even mainframes. They serve multiple users at once over a network and allow the users to share hardware and software resources. Server O.S. provide various functions such as file and print service, or web service. Typical server operating systems are UNIX and Windows 2000.
These run on servers, which are very large personal computers, work stations, or even mainframes. They serve multiple users at once over a network and allow the users to share hardware and software resources. Server O.S. provide various functions such as file and print service, or web service. Typical server operating systems are UNIX and Windows 2000.
7) Describe system calls for file management?
To make changes a file must be opened. This call specifies the file name to be opened, either as an absolute path name or relative to the working directory, and a code of O_RDONLY, O_WRONLY or O_RDWR, meaning open for reading, writing or both. The file descriptor can then be used for reading or writing.
To make changes a file must be opened. This call specifies the file name to be opened, either as an absolute path name or relative to the working directory, and a code of O_RDONLY, O_WRONLY or O_RDWR, meaning open for reading, writing or both. The file descriptor can then be used for reading or writing.
8) Describe about MULTICS?
MULTICS is described as having a series of concentric rings, with the inner ones being more privileged than the outer ones. When a procedure in an outer ring wanted to call a procedure in an inner ring, it had to make the equivalent of a system call which is a TRAP instruction. MULTICS hardware made it possible to designate individual process as protected against reading, writing, or executing.
MULTICS is described as having a series of concentric rings, with the inner ones being more privileged than the outer ones. When a procedure in an outer ring wanted to call a procedure in an inner ring, it had to make the equivalent of a system call which is a TRAP instruction. MULTICS hardware made it possible to designate individual process as protected against reading, writing, or executing.
9) Describe about threads?
Different threads in a process are not quite as independent as different process. All threads share the same global variables as they have the same address space. One thread can read, write, or even completely wipe out another threads stack.
Different threads in a process are not quite as independent as different process. All threads share the same global variables as they have the same address space. One thread can read, write, or even completely wipe out another threads stack.
10) Describe the mechanism of upcall?
When the kernel knows that a thread has blocked, the kernel notifies the processes run time system, passing as parameters on the stack the number of the thread in question and a description of the event that occurred. The notification happens by having the kernel activate the run-time system at a known starting address, roughly analogous to a signal in UNIX.
When the kernel knows that a thread has blocked, the kernel notifies the processes run time system, passing as parameters on the stack the number of the thread in question and a description of the event that occurred. The notification happens by having the kernel activate the run-time system at a known starting address, roughly analogous to a signal in UNIX.
11) Give an example of page replacement in the areas of computer design?
Majority of the computers have more than one memory caches consisting of 32-byte or 64-byte blocks of memory. Whenever a cache is full then some part of the block should be chosen for removal. This problem is precisely the same page replacement except on a shorter time scale.
Majority of the computers have more than one memory caches consisting of 32-byte or 64-byte blocks of memory. Whenever a cache is full then some part of the block should be chosen for removal. This problem is precisely the same page replacement except on a shorter time scale.
12) Describe about preemptive scheduling algorithm?
A preemptive scheduling algorithm picks a process and lets it run for a maximum of some fixed time. If it is still running at the end of the time interval, it is suspended and the scheduler picks another process to run. Doing preemptive scheduling requires having a clock interrupt occur at the end of the time interval to give control of the CPU back to the scheduler.
A preemptive scheduling algorithm picks a process and lets it run for a maximum of some fixed time. If it is still running at the end of the time interval, it is suspended and the scheduler picks another process to run. Doing preemptive scheduling requires having a clock interrupt occur at the end of the time interval to give control of the CPU back to the scheduler.
13) Give a case situation where a scheduling is needed?
When an interrupt occurs, a scheduling decision may be made. If the interrupt came from an I/O device that has now completed its work, some process that was blocked waiting for the I/O may now be ready to run. It is up to the scheduler to decide if the newly ready process should run or not.
When an interrupt occurs, a scheduling decision may be made. If the interrupt came from an I/O device that has now completed its work, some process that was blocked waiting for the I/O may now be ready to run. It is up to the scheduler to decide if the newly ready process should run or not.
14) Describe about checkpointing?
Checkpointing a process means that its state is written to a file so that it can be restarted later. The checkpoint contains not only the memory image, but also the resource state, that is, which resources are currently assigned to the process. To be most effective, new checkpoints should not overwrite old ones but should be written to new files. Whole sequences of checkpoint files are accumulated due to the process getting executed.
Checkpointing a process means that its state is written to a file so that it can be restarted later. The checkpoint contains not only the memory image, but also the resource state, that is, which resources are currently assigned to the process. To be most effective, new checkpoints should not overwrite old ones but should be written to new files. Whole sequences of checkpoint files are accumulated due to the process getting executed.
15) Describe the two phases of two-phase locking?
In the first phase, the process tries to lock all the records it needs, one at a time. If it succeeds, it begins the second phase, performing its updates and releasing the locks. No real work is done in the first phase.
In the first phase, the process tries to lock all the records it needs, one at a time. If it succeeds, it begins the second phase, performing its updates and releasing the locks. No real work is done in the first phase.
16) Explain about deadlocks in operating systems?
Deadlock is a potential problem in any operating system. It occurs when a group of processes each have been granted exclusive access to some resources, and each one wants yet another resource that belongs to another process in the group. All of then are blocked and non will ever run again.
Deadlock is a potential problem in any operating system. It occurs when a group of processes each have been granted exclusive access to some resources, and each one wants yet another resource that belongs to another process in the group. All of then are blocked and non will ever run again.
17) Explain about the paging systems?
Paging systems can be modeled by abstracting the page reference string from the program and using the same reference string with different algorithms. These models can be used to make some predictions about paging behavior. Attention to issues such as determining the working set, memory allocations, and page size are required.
Paging systems can be modeled by abstracting the page reference string from the program and using the same reference string with different algorithms. These models can be used to make some predictions about paging behavior. Attention to issues such as determining the working set, memory allocations, and page size are required.
Posted in: Operating Systems
0 comments:
Post a Comment