Computer Knowledge

Operating Systems

1,344 Questions

Test your computer knowledge with these questions on operating systems. The content covers various platforms including Unix, Linux, Windows, Android, and Macintosh. These questions are commonly asked in the computer knowledge sections of banking and government exams.

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Operating Systems Questions

Multiple choice

How can we create a method that checks for messages in the message queue?

 
  1. Public Boolean isTimerRunn(){
     Return mHandler.hasMessages(0);
}

  2. Private Boolean isTimerRunn(){
     Return mHandler.hasMessages(0);
}

  3. Private Boolean is TimerRunn(){
     Return mHandler.hasMessages(0);
}

  4. Private Boolean isTimerRunn(){
     Return mHandler.queueMessages(0);
}
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The method that checks for messages in the message queue can be defined as follows:

Private Boolean isTimerRunn() {
 Return mHandler.hasMessages(0);
}
Multiple choice

Which of the following codes will record the current system time and send a message to the handler starting the timer and remove any existing message before sending the next one?

 
  1. Private void startTimer(){
   mSt=System.currentTimeMillis();
   mHandler.removeMessages(0);
   mHandler.sendEmptyMessage(0);
}

  2. Private void startTimer(){
   mSt=System.currentTime();
   mHandler.removeMessages(0);
   mHandler.sendEmptyMessage(0);
}

  3. Private void startTimer(){
   mSt=System.currentTimeMillis();
   mHandler.removeMessage(0);
   mHandler.sendEmptyMessage(0);
}

  4. Private void startTimer(){
   mSt=System.currentTimeMillis();
   mHandler.removeMessages(0);
   mHandler.sendEmptyMessages(0);
}
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The code for recording the current system time and sending a message to the handler, starting the timer and removing any existing messages before sending the next one is as follows:

Private void startTimer() {
 mSt = System.currentTimeMillis();
 mHandler.removeMessages(0);
 mHandler.sendEmptyMessage(0);
}
Multiple choice

A processor uses 2-level page tables for virtual to physical address translation. Page tables for both levels are stored in the main memory. Virtual and physical addresses are both 32 bits wide. The memory is byte addressable. For virtual to physical address translation, the 10 most significant bits of the virtual address are used as index into the first level page table while the next 10 bits are used as index into the second level page table. The 12 least significant bits of the virtual address are used as offset within the page.Assume that the page table entries in both levels of page tables are 4 bytes wide. Further, the processor has a translation look-aside buffer (TLB), with a hit rate of 96%. The TLB caches recently used virtual page numbers and the corresponding physical page numbers. The processor also has a physically addressed cache with a hit rate of 90%. Main memory access time is 10 ns, cache access time is 1 ns, and TLB access time is also 1 ns.

Suppose a process has only the following pages in its virtual address space: two contiguous code pages starting at virtual address 0x00000000, two contiguous data pages starting at virtual address 0×00400000, and a stack page starting at virtual address 0×FFFFF000. The amount of memory required for storing the page tables of this process is

  1. 8 KB

  2. 12 KB

  3. 16 KB

  4. 20 KB
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Multiple choice

Which of the following is not the cursor movement commands?

  1. n

  2. a
  3. $

  4. j
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In vi editor: 'n' finds next occurrence, 'j' moves down, '$' moves to end of line - all cursor movements. However, 'a' switches to insert mode AFTER current cursor position to append text. It's not a cursor movement command but rather a mode-switching command for text entry.

Multiple choice

Which command will be used with vi editor to append text at the end of line?

  1. A

  2. a

  3. i

  4. I
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In vi editor, 'a' (append) switches to insert mode and places the cursor AFTER the current character position, allowing you to append text. This is different from 'A' which appends at end of line, 'i' which inserts BEFORE cursor, and 'I' which inserts at beginning of line. The lowercase 'a' specifically appends at the end of current cursor position.

Multiple choice

Unix was first installed in

  1. IBM - 360

  2. PDP/11

  3. PDP/7

  4. CRAY
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Unix was first developed on and installed on the PDP/7 in 1969, then rewritten for the PDP/11 in 1971-1972. The PDP/11 version became the foundation for later Unix development. IBM-360 and CRAY were mainframe/supercomputer architectures unrelated to early Unix.

Multiple choice

The OS which utilizes more than one processor is called

  1. multiprogramming

  2. ms-dos

  3. time-sharing

  4. multiprocessing
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Multiprocessing refers to systems that use multiple processors or processor cores to execute tasks. Multiprogramming refers to running multiple programs on a single processor, time-sharing divides processor time among users, and MS-DOS is a single-user single-tasking OS.

Multiple choice

To copy system files on the disk in target disk, we use

  1. copy

  2. move

  3. sys

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The SYS command (in DOS/Windows) is used to copy system files (IO.SYS and MSDOS.SYS in DOS) to a target disk to make it bootable. The copy command copies regular files, move transfers files, and the sys command specifically handles hidden system files needed for booting.