COMSCI 2101 - Device Management Part 1

Virtual Device

A combination of dedicated and shared devices. They're dedicated devices that have been transformed into shared devices.

Device Management

It monitors the status of each device, enforce present policies, and allocates devices and deallocates them at two levels.

Process Level and Job Level

Device management deallocates devices into two levels:

Dedicated
Shared
Virtual

Types of Devices:

Dedicated Devices

- assigned to only one job at a time
- serve that job for the entire time it's active or until it releases them

Dedicated Device

What type of device is the printer?

Shared Devices

These devices can be assigned to several processes.

Direct Access Storage Device

Meaning of DASD.

Direct Access Storage Device (DASD)

This device can be shared by several processes at the same time by interleaving their requests.

Spooling Program

A printer converted into shareable devices through a?

Universal Serial Bus Controller

acts as an interface between the OS, device drivers, and applications attached via USB host.

Devices can be flash memory, cameras, scanners, musical keyboards.

127 different devices

one USB host can accommodate up to?

identification number

Each devices is identified by the USB host controller with a unique ___________ __________, that allows many devices to exchange data with the computer using the same USB connection.

Storage Media

A physical device that receives, stores, and allows users and programs to access electronic data. This might be inside a computer or other device or
attached to a system externally, either directly or over a network.

Storage Media

What kind of media are CD ROM, DVD ROM, DAT tape, DLT tape, disk drives, SSD, Flash Drive?

Sequential Access Storage Media
Direct Access Storage Devices (DASD)

Storage media are divided into two groups:

Sequential Access Storage Media

store records sequentially, one after another

Direct Access Storage Devices (DASD)

store either sequential or direct access files

Magnetic Tape

developed for routine secondary storage in early computer systems and features records that are stored serially, one after other.

Magnetic Tape

To access a single record, the tape must be mounted and fast-forwarded until the desired position is located.

Density of the Tape (Magnetic)

Determined by the number of characters that can be recorder per inch, such as (1600 bpi)

Bytes per Inch

Meaning of BPI.

individually or grouped into blocks

Records can be stored?

space

If the records are stored individually, each record would need to be separated by a _______ to indicate its starting and ending places.

Blocking

Way of grouping the record into blocks before recording them on tape.

Application Program

The number of records is determined by the?

Transfer Rate

The rate at which data is transferred from sequential access media. Can be measured in either bpi and ips.

ips = density * transport speed

formula of transport rate of sequential access storage media

Access Time

total time required to access data in secondary storage.