Presentation on theme: "LIS508 lecture 4: storage & output devices Thomas Krichel 2002-10-21."— Presentation transcript:
LIS508 lecture 4: storage & output devices Thomas Krichel
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, 8bit, 16bit and 32bit, 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 FAT12 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 FAT32 format if larger than 512Mb –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.