OS topic 13 – Input/output

Question 1

What is a device driver?

A device driver is a piece of s_________ that allows your computer’s operating system to communicate and work with hardware devices.

It serves as a t__________ between the __________________ and the specific hardware, helping them understand each other.

Answer 1

software
translator
operating system

Question 2

Device Drivers

When you connect a new hardware device to your computer, like a printer or a graphics card, the device driver enables the operating system to s_____ and r_______ data to and from that device.

Answer 2

send and receive

Question 3

Device Drivers

True or false
Without device drivers, your computer wouldn’t be able to use or control the connected hardware properly.

Answer 3

True

Question 4

Device Drivers - Problem

Device drivers run in k_______ mode with access to c_______ operating system data; if a driver has b______, then it may well crash the entire system.

Answer 4

kernel mode
critical OS data
bugs

Question 5

Device Drivers - Problem

Why might a commercial OS may restrict installation to drivers that have been appropriately signed after passing thorough testing.

Answer 5

To avoid damage to their reputation.
As mentioned earlier, a buggy driver can crash the entire system!!!

Question 6

Bus interfaces

What is a bus?
A bus is an i___________ to which several devices can be connected at the same time.

Answer 6

interface

Question 7

Bus interfaces

What are ‘data transfer protocols’

Data transfer protocols are sets of rules and conventions that define how data is e___________ between devices or systems over a n__________.

Answer 7

exchanged
network

Question 8

Bus interfaces

What data transfer protocols are usually used by buses?

There are many, but one example is
PCI (P___________ C__________ I_____________):

PCI is a standard bus protocol used for communication between internal components in a computer, such as graphics cards, network cards, and storage devices. It supports high-speed data transfer.

Answer 8

Peripheral Component Interconnect

Question 9

Bus Interfaces

A bus is an interface to which several devices can be connected at the same time; this requires s_______________ data transfer protocols and a way of identifying different devices.

Answer 9

standardised

Question 10

Bus Interfaces

The data transfer protocols are implemented through a s_____ of software routines.

Answer 10

stack

Question 11

Bus Interfaces

What is meant by ‘a stack of software routines’?

A “stack of software routines” typically refers to a collection or s________ of software routines, where each routine represents a specific set of instructions or operations that perform a particular task.

The term “stack” is often used metaphorically to describe the o__________ or arrangement of these routines in a h___________ manner.

Answer 11

sequence
organisational
hierarchical manner

Question 12

Bus Interfaces

Bus-connected devices need to i_____________ themselves so that they are treated appropriately.
USB, for example, allows each peripheral to describe itself to the host computer when first plugged in.

Answer 12

identify themselves

Question 13

Bus Interfaces

True or false

An example of how the device describes itself could be: Audio, video, etc.

Answer 13

True

Question 14

Bus Interfaces

There is also a configuration phase where for example the host computer and peripheral device negotiate d_____ rates and, if necessary, a specialised driver is located and loaded into the k______.

Answer 14

data rates
kernel

Question 15

Bus Interfaces

True or false?
A bus such as USB, as well being used to connect devices, must also be thought of as an I/O device in its own right.

Answer 15

True

Question 16

Bus Interfaces - The major and minor numbering system

The major and minor numbering system is a convention used in operating systems (OS) to identify and manage different d_______ or resources, particularly in the context of device drivers.

Answer 16

devices

Question 17

Bus Interfaces - The major and minor numbering system

Devices receive a major and a minor device number when the system b________:

Answer 17

Devices receive a major and a minor device number when the system boots:

Question 18

Bus Interfaces - The major and minor numbering system

Each different type of device gets a new major number, but two devices of the s______ type share a major number and have different minor numbers.

Answer 18

same type

Question 19

One major classification used by most OSs is into character and block devices.

What classification would a keyboard be?
What classification would a disk drive be?

Answer 19

Keyboards generate a stream of characters, as do mice, and these can be handled one byte (or character) at a time.

Other devices, for example secondary storage such as disk drives, always transfer data in large fixed-size blocks.

Question 20

The hardware interface

I/O registers provide the lowest-level interface to hardware, and typically have three different roles:

1. d_______ register:
2. s__________ register:
3. c__________ register:

Answer 20

data
status
control

Question 21

The hardware interface - I/O registers

The data register
It holds the data that is to be t___________

Answer 21

transferred

Question 22

The hardware interface - I/O registers

The status register
Indicate for example whether more data is w___________ to be collected or whether the I/O device is b_______ and cannot yet accept more data.

Answer 22

waiting
busy

Question 23

The hardware interface - I/O registers

The controls register

Set o________, for example whether data is to be read from or written to the device.

Answer 23

options

Question 24

Data Transfers - Polled I/O

There are _________ techniques used to control the transfer of data between m______ memory and an I/O device

Answer 24

three
main memory

Question 25

Data Transfers - Polled I/O

Poll the device: In this context, “polling” means that the processor regularly c_______ or q______ the I/O device to see if there is any new information or if a specific event has occurred.

Answer 25

checks or queries

Question 26

Data Transfers - Polled I/O

One technique used to control the transfer of data between main memory and an I/O device is for the processor to p____ the device until an I/O event occurs.

Answer 26

poll

Question 27

Data Transfers - Polled I/O

Polling is a useful technique in complex systems.

Answer 27

False

Polling is a useful technique in simple embedded systems

Question 28

Data Transfers - Polled I/O

There are problems using it in a personal computer. The main problem is that it uses busy waiting: the processor is t____ up until I/O is complete.

True or false?
In a multitasking system it would be better for a context switch to occur so that another process can be executed while the I/O is in progress.

A further problem is that it is difficult to deal with multiple I/O devices: the polling l____ would have to check every possible device and be executed frequently so that no events are missed.

Answer 28

tied up

True
loop

Question 29

Data Transfers - Interrupt-driven I/O

Interrupt-driven I/O is much better suited to the needs of a personal computer than polling, because there is no b_____ w______:
the processor is never tied up in l_____ while waiting for slow I/O devices, so overall p__________ of a system can be much better.

Answer 29

busy waiting
loops
performance

Question 30

Data Transfers - Interrupt-driven I/O

True or false?
With interrupt-driven I/O, the OS hardware signals an interrupt whenever an I/O operation is completed;
that is whenever an input arrives, or an output operation finishes and the device is ready for another operation.

Answer 30

False

The I/O hardware signals an interrupt.

Question 31

Data Transfers - Interrupt-driven I/O

Interrupt-driven I/O is much better suited to the needs of a personal computer than polling because There is no busy waiting:

Question 32

Data Transfers - Interrupt-driven I/O

True or false?

There is an overhead in handling each interrupt.

Answer 32

True

Question 33

Data Transfers - Direct memory access I/O

A direct memory access (DMA) controller is a device that can transfer data directly between _______ devices and main memory without involving the p___________.

Answer 33

I/O
processor

Question 34

Data Transfers - Direct memory access I/O

The DMA controller itself is a device with its own I/O r_________ that the operating system can use to specify what transfer is to be made.

Answer 34

registers