LIS 508 lecture 4 storage output devices Thomas

LIS 508 lecture 4: storage & output devices Thomas Krichel 2002 -10 -21

Today we have fun with • Output devices – Fundamental concepts – Hardcopies – Softcopies • Storage devices – disks • magnetic • optical

Literature • Output devices – Hutchinson and Sawyer chapter 3, part 2 • Storage devices – Hutchinson and Sawyer chapter 4

Fundamental concepts I • Pixel – A very small element of a picture – Inside the pixel color and brightness is fixed – All the pixels are created by the computer • Resolution – Number of pixels per inch – Or total number of pixels, confusion

Fundamental concepts II • Red-blue-green model. – Add colors red blue and green to various degrees to get pixels of any color – Additive model • Cyan-Magenta-Yellow – Uses basic color cyan, magenta, yellow, to absorb light on the surface – Subtractive color model

Output comes in two forms • Tangible or hardcopy output – Card puncher – Printer • Intangible or softcopy output – Monitor display screens – Loudspeaker output

Hardcopy to printers • Printer prints – character symbols – Graphics • Output quality is measured in dpi dots per inch • Printers vary from 60 to 1500 dpi • 600 dpi seems common

Types of printers: impact • Forms characters or images by mechanic strikes of a print hammer or wheel. • One example is a typewriter. • Most common form is the dot matrix printer – – – Head with small pins (9, 18, 24) Strike ribbon against paper Do 72 to 144 dpi, 30 to 400 chars Noisy Image may smear

Types of printers: non-impact • Form characters and images without physical contact • Less moving parts, less noise • Two forms – Laser printer – Inkjet printer

Laser printer • Images are produced on a drum • A laser beam sets electrical charge on dots on the drum • Magnetically charged powder called toner flies to the electrified dots on the drum • The drum rolls the toner on the paper • A second drum burns the toner on the paper

Laser printer performance • Can print 200 pages per minute provided that the computer can chunk out the data that fast • Can print a lot of different fonts • More fancy models can even do color • Use a page description language to generate the images

Inkjet printer • Spray tiny, electrically charged drops of ink from 64 nozzles through holes in a matrix onto paper • There are usually four cartages of colored ink (cyan, magenta, yellow, black) • Head moves around and software says where to spray

Inkjet printer performance • Can print color at much less cost than laser printer • Lower resolution than a color laser printer • Slow, one page may take up to 10 minutes • More expensive to operate than a color laser printer when you have to print a lot of color.

multifunction printers • Device that can print, scan, copy and fax • When one component is kaputt, you can not indulge in any of the activities

Softcopy output: monitor • Size is measured diagonally from corner to corner in inches, not the size of the viewing area • Common sizes are 13, 15, 17, 19, 21 • There are two types – Cathode-ray tube CRT – Flat panel displays • All display an image through a number of pixels, individual dots that make it up

Display quality • Dot pitch is the amount of space between adjacent pixels, usually measure in millimeters • Resolution is the number of pixels measured as horizontal pixel number × vertical pixel number. • Refresh rate is the number of times per second the pixels are recharged. > 75 is ok • Color dept, 8 bit, 16 bit and 32 bit, true color. It is often not necessary to have true color. It is better to have higher resolution and less colors.

Types of flat panel monitors • Passive matrix display: one transistor controls a whole row or column of pixels. – good for monochrome – but not for color. – less expensive – Lower energy consumption • Active matrix display, aka thin film transmission TFT: each pixel has its own transistor

CRT monitors • Have a three rays that paint red blue and green • They emit beams that hit phosphate in the screen surface • Light is emitted • Analogue technology

Moving from CRT to TFT • Video card still emit analog beam signals to the monitor. • They have to be converted to the flat panel signal that is digital • Causes some performance losses. • Slow conversion to flat panel technology • Likely to be taken up outside IT, like in art for example

RAM and disks • RAM is random access memory. • It is the operational main storage on a computer. • It is live memory. When the computer is switched of it dies. • Therefore we need to store on other devices, that store when switched off. • The most important are disks.

Structure of a disk • Disks are round devices divided into tracks and sectors. • A hard disk may have several physical disks. All tracks on the same location in different disks from a cylinder. • Disks are divided into sectors. – A sector is usually 571 bytes long – 512 bytes are used by the user – The rest is reserved for disk operation • The disk spins, a head reads and writes data.

Data integrity • The special data in each sector is kept there to try ensure that the user data is safe. • It contains a summary of the user data. • When the summary and the user data no longer match, the summary can be used to correct the user data. • Modern disks can monitor if they are a in good shape, and move data from good to bad sectors.

Formatting a floppy • Physical formatting: – writing tracks – writing sectors • Logical formatting: – labeling each sector – create boot record – windows: create file allocation table (FAT)

Formatting a hard disk • That is the same as formatting a floppy but • Between physical and logical formatting, the hard disk may be partitioned. • This allows for several logical disks on the same physical disk • Therefore the boot record is more complicated than on the floppy and called a master boot record MBR. • Example: dual boot Linux/Windows machine

Windows logical disks • Floppies use FAT 12 format – The boot records is exactly one sector long – therefore called the boot sector – Does not allow for long file names • The logical disks on a hard disks may use FAT 32 format if larger than 512 Mb – System area • Boot record • FAT – User area – Can handle disks of the size of 2 tera bytes

disk architecture on a PC: IDE • IDE integrated device electronics is the classic architecture. An IDE controller chip allows for 2 times 2 disks – primary / secondary – master / slave • The master/slave setup is controlled by jumper settings. Consult manufacturer's web site.

disk architecture on a PC: SCSI • SCSI small computer systems interface allows to daisy chain many devices and gives control of the hard disk to the computer, resulting in – faster operation – more expensive – less standardized • not as popular as predicted.

optical disks • CD-ROMs can store up to 6 Mega Bytes • CD-R holds the same storage, it is recordable once. • CD-RW are read and writable, but does not have the same capacity, because it uses some magnetic technology. • DVDs can hold up to 17 Giga Bytes. Used by the contents industries.

backups • There is a song of the Beatles… • The backup utility is based in the “system tools” section of programs/accessories. • It also has an emergency repair tool, that lets you fix things. • It is best to define a backup job, and then run it at scheduled times. • Time between jobs needs to be chosen with care.

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