Device Management Part 1 Flashcards
Device management can be deallocated at two levels
Process (task) level
Job level
Types of Devices
- Dedicated devices
- Shared devices
- Virtual 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 Devices
Examples of dedicated devices
- Tape drives
- Printer
- Scanner
- Plotters
can be assigned to several processes
Shared devices
can be shared by several processes at the same time by interleaving their requests.
Direct Access Storage Device (DASD)
What type of device is Direct Access Storage Device (DASD) ?
Shared device
- a combination of dedicated and shared devices.
- they’re dedicated devices that have been transformed into shared devices.
Virtual device
a printer converted into sharable devices through a ____
Spooling program
Reroutes all print requests to a disk
Spooling program
-acts as an interface between the OS, device drivers, and applications attached via USB host.
Universal Serial Bus (USB) Controller
One USB host can accommodate up to ___ different devices
127
One USB host can accommodate up to ___ different devices
127
Each devices is identified by the _____ with a unique identification number, that allows many devices to exchange data with the computer using the same USB connection.
USB host controller
A physical device that receives, stores, and allows users and programs to access electronic data.
Storage media
Examples of storage media
- CD ROM
- DVD ROM
- DAT tape
- DLT tape
- disk drives
- SSD
- Flash Drive
The _________ might be inside a computer or other device or attached to a system externally, either directly or over a network.
Storage media
Storage media are divided into two groups
- Sequential access storage media
- Direct Access Storage Devices (DASD)
store records sequentially, one after the other
Sequential access storage media
store either sequential or direct access files
Direct Access Storage Devices (DASD)
- Developed for routine secondary storage in early computer systems and features records that are stored serially, one after other.
- The length of these records is usually determined by the application program and each record can be identified by its position on the tape.
- To access a single record, the tape must be mounted and fast-forwarded until the desired position is located.
Magnetic tape
Nine-track magnetic tape with three characters records using _____.
odd parity
A 1/2-inch wide reel of tape, typically used to back up a main frame computer, can store ____ of characters, or bytes, per inch.
thousands
Determined by the number of characters that can be recorded per inch, such as (1600 bpi).
Density of the Tape
BPI means
Bytes per inch
If the records are stored individually, each record would need to be separated
by a ___ to indicate its starting and ending places.
space
Way of grouping the record into blocks before recording them on tape.
Blocking
The number of records in a block is determined by the ______.
application program
- The rate at which data is transferred from sequential access media
- Can be measured in inches per second (ips)
Transfer Rate
Total time required to access data in secondary storage.
Access time
Total time required to access data in secondary storage.
Access time
