CS 300

• Operating System : The software that runs on the bare hardware of a computer and provides essential support for users to develop and use applications in an efficient and safe manner.
• Would this task require OS support?Input a character from the keyboard. (Y or N)

  Y
• Would this task require OS support?Invoke a high-level matrix manipulation system. (Y or N)

  N
• Would this task require OS support?Allocate n bytes of memory for a new data structure. (Y or N)

  Y
• Would this task require OS support?Load a program into memory. (Y or N)

  Y
• Would this task require OS support?Change the layout of a document. (Y or N)

  N
• Would this task require OS support?Call a library function. (Y or N)

  Y
• Would this task require OS support?Call a function defined within the current program. (Y or N)

  N
• Would this task require OS support?Exit current program. (Y or N)

  Y
• Would this task require OS support?Sleep for n seconds. (Y or N)

  Y
• Abstraction : The act of removing unimportant details or attributes of objects in order to construct more general and less complex objects.
• Virtualization : The act of creating the illusion of having one or more objects with more desirable characteristics than the real object.
• Multiprogramming : A technique that keeps several programs active in memory and switches execution among the different programs to maximize the use of the CPU and other resources.
• Time sharing : An extension of multiprogramming where the CPU is switched periodically among all active computations to guarantee acceptable response times to each user.
• Multiprogramming generally improves overall system performance. (T or F)

  T
• The main objective of time sharing is to improve resource utilization. (T or F)

  F
• Multiprogramming and time-sharing are not used together. (T or F)

  F
• In a hypothetical system, the average computation spends 50% of total time using the CPU and the remaining 50% waiting for I/O.To achieve best CPU utilization, _ computations should run simultaneously.

  a)2

  b) more than 2

  c) all available

  Answer: B
• In a hypothetical system, the average computation spends 50% of total time using the CPU and the remaining 50% waiting for I/O.The use of time sharing will _.

  a)speed up all computations

  b) guarantee reasonable response to each computation

  c) improve resource allocation

  Answer: B
• Processes p1 and p2 share a single CPU and 2 independent I/O devices. Each process executes a compute-bound phase of 10 time units followed by an I/O-bound phase of 10 units.Without multiprogramming, the total execution time of both processes is _ time units.

  a)20

  b) 30

  c) 40

  Answer: C
• Processes p1 and p2 share a single CPU and 2 independent I/O devices. Each process executes a compute-bound phase of 10 time units followed by an I/O-bound phase of 10 units.With multiprogramming, the total execution time of both processes is _ time units.

  a)20

  b) 30

  c) 40

  Answer: B
• Processes p1 and p2 share a single CPU and 2 independent I/O devices. Each process executes a compute-bound phase of 10 time units followed by an I/O-bound phase of 10 units.If p1 and p2 use time sharing, the total execution time of both processes is ____ time units.

  a)20

  b) 30

  c) 40

  Answer: B
• Kernel : The minimal set of functions necessary to maintain the system resources safely and efficiently.
• Privileged instruction : An instruction set that performs critical operations that access I/O devices and the CPU's status and control registers.
• Kernel mode : The CPU state where both privileged and non-privileged instructions may be used.
• User mode : The CPU state where only non-privileged instructions may be used.
• Kernel functions may be invoked by _.

  a)only system call libraries

  b) only system call or general libraries

  c) any program

  Answer: C
• Privileged instructions may be executed by _.

  a)only the kernel

  b) the kernel and system call libraries

  c) any program

  Answer: A
• An application that needs to access an I/O device could not be written without _.

  a)kernel and library functions

  b) kernel functions

  Answer: B
• The kernel can execute _ instructions.

  a)only privileged

  b) both privileged and non-privileged

  Answer: B
• Graphical User Interface (GUI) : Presents various icons on the screen, which the user can click on in different ways to invoke services associated with the icons, or to reveal pull-down menus for additional tasks.
• OS shell : A command interpreter that accepts and interprets textual commands issued by the user via a keyboard.
• Shell script : A program that implements a new operation by combining multiple commands and control statement into one named unit interpreted by the shell.
• A script can use an iteration variable, i. The value $i of i can be used to create a different name in each iteration. The script below creates 10 directories named D0, D1, ..., D9, where MKDIR is the command to make a directory.

  FOR i in 0 1 2 3 4 5 6 7 8 9 DO

  MKDIR D$i.d

  DONE

  To create the same directories using a GUI, the user must perform some number of right and left-clicks, type some number of characters, and press Enter several times.The required number of right clicks is 10 .
• A script can use an iteration variable, i. The value $i of i can be used to create a different name in each iteration. The script below creates 10 directories named D0, D1, ..., D9, where MKDIR is the command to make a directory.

  FOR i in 0 1 2 3 4 5 6 7 8 9 DO

  MKDIR D$i.d

  DONE

  To create the same directories using a GUI, the user must perform some number of right and left-clicks, type some number of characters, and press Enter several times.The number of characters typed is 20 .
• A script can use an iteration variable, i. The value $i of i can be used to create a different name in each iteration. The script below creates 10 directories named D0, D1, ..., D9, where MKDIR is the command to make a directory.

  FOR i in 0 1 2 3 4 5 6 7 8 9 DO

  MKDIR D$i.d

  DONE

  To create the same directories using a GUI, the user must perform some number of right and left-clicks, type some number of characters, and press Enter several times.The number of times Enter is pressed is 10 .
• System call : A request from an application for an OS service.
• Supervisor call (kernel call) : A privileged instruction that automatically transfers execution control to a well-defined location within the OS kernel.
• A system call is a _.

  a)privileged instruction

  b) library function

  c) kernel function

  Answer: B
• A supervisor call is a_.

  a)privileged instruction

  b) library function

  c) kernel function

  Answer: A