1.4 Operating-System Operations Flashcards
An operating system provides the environment within which programs are _______.
executed
The initial program that a computer runs when powered up or rebooted is called the _______.
bootstrap program
The bootstrap program is typically stored in _______.
firmware
The bootstrap program initializes all aspects of the system, including _______.
CPU registers, device controllers, memory contents
The bootstrap program must locate the _______ and load it into memory.
operating-system kernel
Once the kernel is loaded and executing, it starts providing _______ to the system and its users.
services
System programs loaded into memory at boot time become _______.
system daemons
On Linux, the first system program that starts many other daemons is _______.
systemd
If there are no processes to execute, an operating system will sit quietly, waiting for something to _______.
happen
Events are almost always signaled by the occurrence of an _______.
interrupt
A trap (or an exception) is a software-generated interrupt caused by an error or a specific request from a user program that an operating-system service be performed by executing a _______.
system call
An example of an error that can cause a trap is _______.
division by zero
Another example of an error that can cause a trap is _______.
invalid memory access
One of the most important aspects of operating systems is the ability to run multiple programs, as a single program cannot, in general, keep either the CPU or the I/O devices busy at all times. This is known as _______.
multiprogramming
In a multiprogrammed system, a program in execution is termed a _______.
process
The operating system keeps several processes in _______ simultaneously.
memory
When a process needs to wait for some task, such as an I/O operation, the CPU would switch to _______ in a multiprogrammed system.
another process
In a non-multiprogrammed system, the CPU would sit _______.
idle
Multitasking is a logical extension of _______.
multiprogramming
In multitasking systems, the CPU executes multiple processes by _______ among them.
switching
When a process executes, it typically executes for only a _______ time before it either finishes or needs to perform I/O.
short
Interactive I/O may take a long time to complete, often bounded by the user’s _______ speed.
typing
Having several processes in memory at the same time requires some form of _______ management.
memory
Making the decision of which process will run next is known as _______ scheduling.
CPU
A common method for ensuring reasonable response time in a multitasking system is _______ memory.
virtual
The main advantage of virtual memory is that it enables users to run programs that are larger than actual _______ memory.
physical
Multiprogramming and multitasking systems must also provide a _______ system.
file
To ensure orderly execution, the system must also provide mechanisms for process _______ and communication.
synchronization
The system may ensure that processes do not get stuck in a _______.
deadlock
A properly designed operating system must ensure that an incorrect (or malicious) program cannot cause other programs or the operating system itself to execute incorrectly. True or False?
True
What are the two separate modes of operation in an operating system?
User mode and kernel mode
The bit that indicates the current mode of operation in a computer system is called the _______.
mode bit
In kernel mode, the mode bit is set to _______.
0
In user mode, the mode bit is set to _______.
1
When a user application requests a service from the operating system, the system must transition from _______ to _______ mode.
user mode to kernel mode
The dual mode of operation provides protection for the operating system from _______ users.
errant
Privileged instructions can only be executed in _______ mode.
kernel
An attempt to execute a privileged instruction in user mode is treated as _______.
illegal
Examples of privileged instructions include _______.
- I/O control
- Timer management
- Interrupt management
Intel processors have _______ separate protection rings.
four
In Intel processors, ring 0 is _______ mode.
kernel
ARMv8 systems have _______ modes.
seven
The virtual machine manager (VMM) has more privileges than user processes but fewer than the _______.
kernel
The life cycle of instruction execution in a computer system starts with control residing in the _______.
operating system
System calls provide the means for a user program to ask the operating system to perform tasks reserved for the operating system on the user program’s behalf. True or False?
True
A system call is usually invoked in the form of a _______ to a specific location in the interrupt vector.
trap
When a system call is executed, it is typically treated by the hardware as a _______ interrupt.
software
The kernel examines the interrupting instruction to determine what _______ has occurred.
system call
If a user program fails by executing an illegal instruction, the hardware traps to the _______.
operating system
When a program error occurs, the operating system must terminate the program _______.
abnormally
An appropriate error message is given, and the memory of the program may be _______.
dumped
We must ensure that the operating system maintains control over the ___
CPU
We cannot allow a user program to get stuck in an infinite loop or to fail to call ___ and never return control to the operating system.
system services
To accomplish the goal of maintaining control, we can use a ___.
timer
A timer can be set to interrupt the computer after a specified ___.
period
The period of a timer may be fixed (for example, 1/60 second) or ___.
variable
A variable timer is generally implemented by a fixed-rate clock and a ___.
counter
The operating system sets the ___.
counter
Every time the clock ticks, the counter is ___.
decremented
When the counter reaches 0, an ___ occurs.
interrupt
A 10-bit counter with a 1-millisecond clock allows interrupts at intervals from 1 millisecond to ___ milliseconds.
1,024
Before turning over control to the user, the operating system ensures that the timer is set to ___.
interrupt
If the timer interrupts, control transfers automatically to the operating system, which may treat the interrupt as a ___ or may give the program more time.
fatal error
Instructions that modify the content of the timer are ___.
privileged
