Claro Garcia
NT1110 CS & L
April 9, 2014
Chapter 3 Summary In the world of computers, input/output (I/O) devices are utilized to enhance, configure and control data transfer between the computer and external devices in a variety of ways. These devices use ‘ports’ to connect to either internal or external hardware to and from the computer. The ports are then linked to copper circuits and memory that communicate to the computer CPU, RAM and ports. This enables data transfer between these I/O devices and the computer. Nowadays, the Universal Serial Bus (USB) port is considered to be the most important I/O port among all other I/O ports because it has replaced PS/2 (mini DIN) mouse and keyboard, serial (COM), and parallel (LPT) ports in recent computer systems and providing greater speed. A recent computer desktop system has at least four USB ports and can support up to eight front-and-rear mounted USB ports. The three standard types of USB ports are (1) USB 1.1, (2) USB 2.0 a.k.a Hi-Speed USB -and (3) USB 3.0 a.k.a Superspeed USB and use either Series A a.k.a Type A or Series B a.k.a Type B types of connectors. Adding more USB ports can be done by using motherboard connectors for USB header cables, hubs and add-on cards. Serial (COM) I/O ports also known as RS-232 ports are used for external modems, serial mouse, plotters, label printers, serial printers, PDA docking stations, digital cameras and PC-to-PC connections used by file transfer programs such as DirectCable Connection, LapLink and Interlink. These ports come in two forms: DB-9M (male) and DB 25M (male) but only the former is not being used for older systems. This I/O port requires two hardware resources: Interrupt ReQuest (IRQ) and I/O port address. Parallel a.k.a Line Printer (LPT) port is one of the most versatile I/O ports and is used by devices such as tape backups, external CD-ROM and optical drives, scanners and removable-media drives like Zip drives. It is different from other I/O ports because it uses two different connector types: IEEE 1284-A port (DB-25F with 1-13 pins on top and 14-25 pins at the bottom) and IEEE-1284-B port (uses 36 connectors, 18 per side). Small Computer Systems Interface (SCSI) is a flexible I/O port that can accommodate devices in addition to hard disk drives such as high-performance and high-capacity hard drives, image scanners, removable-media such as Zip, Jaz and Castlewood Orb, high-performance laser printers, optical drives and tape backups. The major SCSI standards depending on the number, speed and technical details of devices are categorized as Fast, Fast-wide, Ultra, Ultra-wide, Ultra2, Ultra2wide, Ultra 160 and Ultra 320. FireWire a.k.a IEEE 1394, a family of high-speed bidirectional serial transmission ports, is considered as one of the fastest and most flexible port that connects PC to PC, digital devices to PC or digital devices to another digital device. It also supports ‘hot-swapping’ which enables you to add and/or remove device from the FireWire port without shutting down the system and it also supports Networking with Windows XP. Other I/O ports include PS/2 (Mini-DIN) for PS/2 keyboard and mice, Centronics for parallel printers and narrow SCSI devices, 1/8 inch Audio Mini-Jack for speakers, microphones and line-in jacks, SPDIF Digital Audio for home theater systems, MIDI port for MIDI keyboards and RG-6 Coaxial for TV and FM radio tuners.
Additionally, contemporary PCs use input devices such as keyboard and mice, bar code readers, biometric devices and touch screens. Keyboards, the most important device that send commands to the computer, use USB ports and now come in 104-key layout with Windows keys one each side of the space bar and a right-click key next to the right Ctrl key. Mice and other pointing devices now come with trackballs or touchpads and use USB 1.1 or USB 2.0 ports. Game controllers are now usually in forms of game pads that connects through USB or 15-pin parallel connectors. Bar code readers that are usually seen in a point-of-sale locations like the grocery store, library and medical offices to track inventory use either pen-based readers, laser scanners, charge-coupled device (CCD) readers or camera-based readers. Biometric devices prevent access to computers and other electronic devices by comparing fingerprints or other biometric marker from that of the owner of the device. There is also the advent of the voice-activated typing that uses voice-to-text recognition software that does not require the use of keyboard in putting words in a document or letter.
Display types are divided into three categories: Cathode Ray Tube (CRT) monitors that use picture tube, Liquid Crystal Display (LCD) monitors that use liquid crystal cells to polarize light passing through the display and data projectors that clone or replace primary display from a device to the projection screen or wall. Touchscreens enable users to transfer data by pressing icons on the computer device. These devices use LCD or CRT display and incorporates four-wire or five-wire resistive technology, surface wave, touch-on tube or scanning infrared
Determining video connector types is important when choosing a monitor or projector. These types of video connectors differ in physical and specification features. VGA is an analog display standard that has color limits and use DB-15F female connector that plugs into the DB-15M from the monitor. DVI port is used for digital LCD monitors. High-Definition Multimedia Interface (HDMI) supports both audio and video and is commonly used for home theater system. Component/RGB supports high-resolution type of analog audio. S-Video provides better TV, projector, DVD and VCR signal by separating luma and chroma signals. Composite is the lowest-quality video signal supported by PCs that uses single RCA cable and port.
When it comes to printing, there are four primary types: laser (like photocopiers; uses toner cartridges), inkjet a.k.a dispersion printers (used in home-office or small-office; use ink cartridges), thermal (use thermal printer ribbons) and impact (oldest printer technology; use mechanical printhead that presses against an ink ribbon to print characters and graphics).
In addition to these devices are the multimedia devices such as Webcams (take video and still images during live chat and does not include storage capabilities), Digital Camera (records images onto internal or card-based flash memory and is used to transfer images from the camera to the computer), MIDI music and MIDI ports (stored digital samples of musical instruments ), Sound Card (used to record and playback analog audio), Microphones (either built into headsets or use a stand) and Video Capture Card (capture live video from various sources such as camcorders and VCRs)