MAC OS – Unit A

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Understand Storage MediaExploring Data Communication

Types of a Storage Media

Because RAM stores data only when the computer is on, the computer needs a permanent storage device.

Types of Storage Media:

1.Magnetic Storage Devices.

2.Optical Storage Devices

3.Flash Memory

Magnetic Storage Devices

• Magnetic Storage devices are hard disk, tape and floppy disks.

• Hard disk is the most common type of magnetic storage media. It contains several magnetic oxide covered metal patterns that are sealed in a case inside the computer.

• Tape is much slow to be used for every day computer tasks. Tapes are used to make backup copies of data stored on hard disks. Tape provides inexpensive, though slow, archive storage for large companies

• Floppy disk is a flat circle of magnetic metal-oxide enclosed in a hard plastic case. Floppy disks are also called 3 ½” disks because of the size of the plastic case.

TapTapee

Hard Hard diskdisk

Floppy Floppy diskdisk

Optical Storage Devices

Optical Storage Devices are polycarbonate discs coated with a reflective metal on which data is recorded using laser technology as dark spots in the surface of the disc.

The data that these spots represent can be read with a laser light

CD = Compact disk is the first standard output optical device available for personal computers. Its capacity: 700 MB

DVD = Digital video disk is the same size as the CD that’s stores between 4.7 and 15.9 GB depending on whether the data is stored on one or two sides of the disc

Blu-ray DVD or HD-DVD are new types of optical storage devices that are capable of storing 15GB to 50 GB. They are used for storing high definition video.

Blue Ray DVD CD

DVD

Flash Memory

Flash memory is similar to ROM except that it can be written more than once.

Flash memory cards are small portable cards encased in hard plastic to which data can be written and rewritten. They are used in cameras, handheld computers and other devices.

USB flash storage device also called USB drive or Flash drive used for personal computers and are available in different sizes.

USB drives are available in storage capacity of 30 MB to 16 GB of data.

USB drives plug directly into the computer through a port.

Flash Memory Card Flash Storage device

USB Port

Exploring Data Communication

Data communication is the transition of data from one computer to another or to a peripheral device

The computer that originates the message is the sender.

The message is sent over type of channel such as a cable or telephone

The rules that establish an orderly transfer of data between the sender and the receiver are called protocols

The transmission protocol between a computer and its peripheral devices is handled by a device driver .

Device driver is a program that can establish communication because it contains the information about the characteristics of the computer and the device.

Ways of Communication

The data path between the microprocessor, RAM and the peripherals along which communication travels is called the data bus.

Ways of Communication

An external peripheral device must have a corresponding port and cable to connect it to the computer.

Inside the computer, each port connects to a controller card called an expansion card or interface card.

The cards connect to electrical connectors called expansion slots or slots.

Personal computers have several ports called parallel, serial, USB and Ethernet.

Controller card

Expansion Slots

Types of Ports

Parallel port transmits data eight bits at a time. Parallel transmissions are fast but they have an increased risk of interference.

Serial port transmits one bit a time.

SCSI – Small Computer System Interface port provides an interface for more than one peripheral device at the same port. The first is connected directly to the computer through the port and the second device is plugged into a similar device on the first port.

Parallel Port Serial Port

SCSI Port

MIDI Port

USB Port

USB

.USB (Universal Serial Bus) port is a high speed serial port which allows multiple connections at the same port.

The device you install must have a USB port connector, a small rectangular plug.

You can connect multiple devices to a single usb port.

USB flash storage devices plug into USB ports.

For most devices, power is supplied via the USB port.

MIDI

The port for a sound card usually includes jacks for speakers and a microphone which are designed to work with a MIDI (Musical Instrument Digital Interface) card.

Ethernet

You can connect to another computer , a LAN or modem using an Ethernet port.

Ethernet ports allow data to be transmitted at higher speeds.

PC Card

Notebook computers may also include a portable computer card called PC card

PC cards are credit size cards that plug directly into the PC card slot and can contain additional RAM or a hard disk drive