1. 11-1 Display Technologies Hi-resolution displays come in two types: –Each takes an input signal and creates a visible image Cathode ray tube (CRT) - Streams of electrons make phosphors glow on a large vacuum tube. –Monitor Liquid crystal display (LCD) - A flat panel display that uses crystals to let varying amounts of different colored light to pass through it. –Developed primarily for portable computers. –Panel How does a monitor really work –i.e., how does the image get there?

2. 11-2 Video Display –How does a monitor really work –how does the image get there? The video card or graphics card sends video signals to the monitor The video card has it’s own memory and CPU –The Graphics Processing Unit (GPU) receives instructions (from the CPU) to draw an image (bitmap) to the display –The image data (bitmap) will be copied from primary memory to video memory (VRAM) –The video signal is sent periodically ensuring that the monitor is displaying the video image described in the VRAM contents this is complicated, but the video card takes care of everything for us Let’s consider a much simpler output device -- –Daisy wheel printers »“letter quality” printer

3. 11-3 “Other” Devices There are other devices that we have yet to mention that don’t fit nicely into either “input devices” or “output devices” –Floppy drives, –Hard disks –CD-ROM drives –DVD-ROM drives –CD-RW/DVD-RW drives They are input devices to our computer, but can also be output devices. –There’s something else weird about them, consider the type of the input they process –We consider “traditional” input devices those that deal with original data. –And define a classification for devices that handle previously stored data.

4. 11-4 Data Sources Computer data can be: –Original data: Data being introduced to a computing system for the first time. The input device directly samples physical things in the world (printed text, pictures, sound, and other common types of information) and converts them to binary for the computer Think: non-binary inputs that need to be converted Examples: ? –Digitizing: The process of taking an image, audio recording or any other analog data and converting it to a binary format for the computer. Allows our computer (and programs) to represent and manipulate “analog data”

5. 11-5 Data Sources Computer data can be : –Previously stored data or information: Data that has already been processed by a computer and is being stored for later use. The input devices directly reads binary data (the data has already been converted to binary). The binary form of the data is useful only to a computer –Using a CDR as a drink coaster doesn’t count as using binary data Think: Already converted to binary Examples: –music CDs? –It would be useful to have “previously stored data”-devices that can both read and write binary data

6. 11-6 Storage Devices Storage Devices – “Secondary Memory” –used by a computer to Write binary information (store) Read binary information as needed (retrieve) –compared to primary memory, it’s slower but less expensive slower means it takes more time to get a bit from the device –“Secondary” with respect to the Von Neumann model Technically a kind of memory –Can be used to manipulate bits But calling it memory is really incorrect –By Von Neumann’s definition, it is secondary – not required –Take bits from memory and output them to a device »Move papers from desk to cabinet –Take bits from a device and put them in memory »Or move from filing cabinet to desk