In Chapter 2, we discuss what a computer does and how its functions make it such a useful machine.
Files and applications can be quite large, containing thousands or millions of bytes.To make it easier to measure the size of these files, we need units of measure larger than a byte. Kilobytes, megabytes, and gigabytes are therefore simply larger bytes. As shown in this table, a kilobyte (KB)is approximately 1,000 bytes, a megabyte (MB)is about 1 million bytes, and a gigabyte (GB)is around 1 billion bytes. Many business computers can store up to a petabyte of data.
The mouse type you’re probably most familiar with is the optical mouse. An optical mouse uses an internal sensor or laser to detect the mouse’s movement. The sensor sends signals to the computer, telling it where to move the pointer on the screen. Optical mice don’t require a mouse pad, although you can use one to enhance the movement of the mouse on an uneven surface, or to protect your work surface from being scratched. Wireless mice are similar to wireless keyboards in that they use batteries and send data to the computer by radio frequency or Bluetooth technologies.Apple has developed Magic Mouse, the first multitouch wireless mouse. The top surface of the mouse is the button. Use your finger to scroll in any direction, swipe your fingers across the mouse to move through web pages and photos, and tap on the mouse to click and double-click.
Most laptops have an integrated pointing device such as a touch pad (or trackpad), a small, touch-sensitive area at the base of the keyboard. Some laptops incorporate a trackpoint device, a small, joystick-like nub that allows you to move the cursor with the tip of your finger.
A touch screen is a display screen that responds to commands initiated by a touch with a finger or a stylus. Touch screens are becoming the norm on many computing devices, especially smartphones such as the Droid and iPhone, and tablet computers such as the iPad and Samsung Galaxy Tab. Tablets and other touch-screen devices use a virtual keyboard that displays on screen when text input is required. These keyboards show basic keyboard configurations, and use special keys to switch to numeric, punctuation, and other keys.
Digital cameras, camcorders, and cell phones are common devices for capturing pictures and video, and all of them are considered input devices. Scanners can also input images. They work similarly to a photocopy machine, but instead of generating the image on paper, they create a digital image, which you can print, scan, or e-mail.A webcam is a small camera that sits on top of a computer monitor (connected to the computer by a cable) or is built into a laptop or tablet computer. Although webcams are able to capture still images, they’re used mostly for capturing and transmitting live video. Videoconferencing technology lets a person using a computer equipped with a webcam and a microphone transmit video and audio across the Internet.
Closetalk microphones, which are usually attached to a headset, facilitate using speech-recognition software, videoconferencing, or making telephone calls. With a microphone attached to a headset, your hands are free to perform other tasks while you speak, such as making notes or referring to paper documents, and the headset allows you to listen as well.Omnidirectional microphones pick up sounds from all directions at once. These mics are best for recording more than one voice, such as during a conference call when you need to pick up the voices of multiple speakers.Unidirectional microphones pick up sound from only one direction. These are best used for recording podcasts with a single voice or making phone calls over the Internet with only one person on the sender’s end of the call. Clip-on microphones (also called lavalier microphones) are useful in environments such as presentations, where you need to keep your hands free for other activities (such as writing on a whiteboard) or move around the room. Many of these microphones are wireless.
Wireless printing allows you to print without the restriction of wires. Wireless printers let several people print to the same printer from different places.There are two types of wireless printers: WiFi and Bluetooth. Both WiFi and Bluetooth printers have a range of up to approximately 300 feet. WiFi sends data more quickly than Bluetooth.Wireless printers are also great for printing from portable devices. If you’re using a device running Apple’s iOS (such as an iPhone), AirPrint makes printing easy. AirPrint is a feature of iOS that facilitates printing to AirPrint-compatible wireless printers.
An all-in-one printercombines the functions of a printer, scanner, copier, and fax into one machine. Popular for their space-saving convenience, all-in-one printers can use either inkjet or laser technology.A plotter prints oversize pictures that require the drawing of precise and continuous lines, such as maps and architectural plans. Plotters use a computer-controlled pen that provides a greater level of precision than the series of dots that laser or inkjet printers make.A thermal printerworks by either by melting wax-based ink onto ordinary paper (a process called thermal wax transfer printing) or by burning dots onto specially coated paper (a process called direct thermal printing). They are used in stores to print receipts and in airports for electronic ticketing and many models feature wireless technology. Thermal printers are also popular for mobile printing in conjunction with smartphones and similar devices.
Most computers include inexpensive speakers, which are the output devices for sound. These speakers are sufficient to play the standard audio clips you find on the web and usually enable you to participate in videoconferencing or phone calls made over the Internet. However, if you plan to digitally edit audio files or are particular about how your music sounds, then you might want a more sophisticated speaker system, such as one that includes subwoofers (special speakers that produce only low bass sounds) and surround-sound speakers. A surround-sound speaker is a system of speakers and audio processing that envelops the listener in a 360-degree field of sound. Wireless speaker systems are available to help you avoid cluttering up your rooms with speaker wires. If you work in close proximity to other employees or travel with a laptop, you might need to use headphones or earbuds for your sound output to avoid distracting other people. Both devices plug into the same jack on the computer to which speakers connect. Studies of users of portable media players have shown that hearing might be damaged by excessive volume, especially when using earbuds, because they fit into the ear canals. Exercise caution when using these devices.
Random access memory (RAM)is the place in a computer where the programs and data the computer is currently using are stored. RAM is much faster to read from and write to than the hard drive and other forms of storage. Because the entire contents of RAM are erased when you turn off the computer, RAM is the temporary or volatile storage location. To save data more permanently, you need to save it to the hard drive or to another permanent storage device such as a CD or flash drive.Read-only memory (ROM) holds all the instructions the computer needs to start up when it is powered on. The instructions stored in ROM are permanent, making ROM a nonvolatile storage location, which means the data isn’t erased when the power is turned off.
For large portable storage needs, there are portable external hard drives, which are small enough to fit into your pocket and have storage capacities of 4 TB (or larger). These devices are small and lightweight and are enclosed in a protective case. They attach to your computer via the USB port. Most of these portable external hard drives do not use solid-state technology, so care should be taken when transporting them.
We have discussed peripheral devices that input, store, and output data and information. A port is a place through which a peripheral device attaches to the computer so that data can be exchanged between it and the operating system. Although many ports are located on the back of computers, some commonly used ports are placed on the front and sides for easier access when connecting devices such as flash drives or digital and video cameras.
A universal serial bus (USB) portis the port type most commonly used to connect input and output devices to the computer. This is mainly because of a USB port’s ability to transfer data quickly. USB 2.0 ports are the current standard and transfer data at 480 megabits per second (Mbps).The new USB 3.0 standard provides transfer speeds of 4.8 Gbps and charges devices faster than its predecessor. USB 3.0 is quickly becoming the port of choice.
You might also see other ports, such as FireWire 400 and FireWire 800. The FireWire 400 interface moves data at 400 Mbps, whereas the FireWire 800 doubles the rate to 800 Mbps. Devices such as external hard drives, digital video cameras, portable music players, and digital media players all benefit from the speedy data transfer capabilities of FireWire. The FireWire 3200 standard, with data transfer rates of 3.2 Gbps, has been ratified but has yet to reach the market.
Another set of ports on your computer helps you communicate with other computers. A connectivity port can give you access to networks and the Internet. To find a connectivity port, look for a port that resembles a standard phone jack but is slightly larger. This port is called an Ethernet port. Ethernet ports transfer data at speeds up to 10,000 Mbps. You can use an Ethernet port to connect your computer to a digital subscriber line (DSL) or cable modem, or a network. Some computers still feature a second connectivity port that will accept a standard phone line connector. This jack is the modem port. It uses a traditional telephone signal to connect to the Internet over a phone line.Other ports on the back and sides of the computer include the audio and video ports. Audio ports are where you connect headphones, microphones, and speakers to the computer. A video port is needed to attach a monitor to a desktop computer or a second, larger display to a laptop computer. The video graphics array (VGA) port is the port to which older LCD monitors connect.
Another set of ports on your computer helps you communicate with other computers. A connectivity port can give you access to networks and the Internet. To find a connectivity port, look for a port that resembles a standard phone jack but is slightly larger. This port is called an Ethernet port. Ethernet ports transfer data at speeds up to 10,000 Mbps. You can use an Ethernet port to connect your computer to a digital subscriber line (DSL) or cable modem, or a network. Some computers still feature a second connectivity port that will accept a standard phone line connector. This jack is the modem port. It uses a traditional telephone signal to connect to the Internet over a phone line.Other ports on the back and sides of the computer include the audio and video ports. Audio ports are where you connect headphones, microphones, and speakers to the computer. A video port is needed to attach a monitor to a desktop computer or a second, larger display to a laptop computer. The video graphics array (VGA) port is the port to which older LCD monitors connect.
Newer LCD monitors, as well as other multimedia devices such as televisions, DVD players, and projectors, connect to digital video interface (DVI) ports.The latest digital connector designed for use in HD home theater environments is a high-definition multimedia interface (HDMI), a compact audio-video interface that carries both HD video and uncompressed digital audio on one cable.
In Windows 8, the main method of power management is Sleep. When your computer enters Sleep Mode, all of the documents, applications, and data you were using remain in RAM (memory), where they’re quickly accessible when you restart your computer.Hibernate option is similar to Sleep except that your data is stored on your hard drive instead of in RAM and your computer is powered off. This uses much less battery power than Sleep and is a good choice if you won’t be using your laptop for a long time and won’t have the opportunity to charge it.Restarting the system while it’s powered on is called a warm boot. You might need to perform a warm boot if the operating system or other software application stops responding or if you’ve installed new programs.