Information technology

Information technology (IT) is the design, development, implementation, support, and management of computer hardware and software applications. An IT professional is knowledgeable about computer systems and operating systems. A computer system consists of hardware and software components. Hardware is the physical equipment such as the case, storage drives, keyboards, monitors, cables, speakers, and printers. The term software includes the operating system and programs. The operating system instructs the computer how to operate. These operations may include identifying, accessing, and processing information. Programs or applications perform different functions. Programs vary widely depending on the type of information that will be accessed or generated. For example, instructions for balancing a checkbook are very different from instructions for simulating a virtual reality world on the Internet. COMPUTER CASE The computer case provides protection and support for the internal components of the computer. The size and shape of the computer case is usually determined by the motherboard and other internal components. You can select a large computer case to accommodate additional components that may be required in the future. Other users may select a smaller case that requires minimal space. In general, the computer case should be durable, easy to service, and have enough room for expansion. A computer case contains the framework to support the internal components of a computer while providing an enclosure for added protection. Computer cases are typically made of plastic, steel, and aluminum and are available in a variety of styles. The size and layout of a case is called a form factor. There are many types of cases, but the basic form factors for computer cases include desktop and tower. Computer cases are referred to in a number of ways: • Computer chassis • Cabinet • Tower • Box • Housing In addition to providing protection and support, cases also provide an environment designed to keep the internal components cool. Case fans are used to move air through the computer case. As the air passes warm components, it absorbs heat and then exits the case. This process keeps the components of the computer from overheating. There are many factors that must be considered when choosing a case: • The size of the motherboard • The number of external or internal drive locations called bays • Available space • Status Display • Size of power supply In addition to providing protection from the environment, cases help to prevent damage from static electricity. Internal components of the computer are grounded by attachment to the case. NOTE: You should select a case that matches the physical dimensions of the power supply and motherboard. POWER SUPPLY All computers need a power supply to convert alternating-current (AC) power from the wall socket into direct-current (DC) power which is a lower voltage. DC power is required for all of the components inside the computer. The power supply must provide enough power for the components that are currently installed and allow for additional components that may be added at a later time. If you choose a power supply that powers only the current components, it may be necessary to replace the power supply when other components are upgraded. Connectors Most connectors today are keyed connectors. Keyed connectors are designed to be inserted in only one direction. Each part of the connector has a colored wire with a different voltage running through it, as seen in Figure 2. Different connectors are used to connect specific components and various locations on the motherboard: • A Molex connector is a keyed connector used to connect to an optical drive or a hard drive. • A Berg connector is a keyed connector used to connect to a floppy drive. A Berg connector is smaller than a Molex connector. • A 20-pin or 24-pin slotted connector is used to connect to the motherboard. The 24-pin slotted connector has two rows of 12-pins each, and the 20-pin slotted connector has two rows of 10-pins each. • A 4-pin to 8-pin auxiliary power connector has two rows of two to four pins and supplies power to all areas of the motherboard. The 4-pin to 8-pin auxiliary power connector is the same shape as the main power connector, but smaller. There is a basic equation that expresses how three of the terms relate to each other. It states that voltage is equal to the current multiplied by the resistance. This is known as Ohm's Law. V = IR In an electrical system, power (P) is equal to the voltage multiplied by the current. P = VI In an electrical circuit, increasing the current or the voltage will result in higher power. As an example of how this works, imagine a simple circuit that has a 9 V light bulb hooked up to a 9-V battery. The power output of the light bulb is 100-W. Using the equation above, we can calculate how much current in amps would be required to get 100-W out of this 9-V bulb. To solve this equation, we know the following information: P = 100 W V = 9 V I = 100 W/9 V = 11.11 A What happens if a 12-V battery and a 12-V light bulb are used to get 100 W of power? 100 W / 12 V = 8.33 amps This system produces the same power, but with less current. Computers normally use power supplies ranging from 200-W to 500-W. However, some computers may need 500-W to 800-W power supplies. When building a computer, select a power supply with sufficient wattage to power all of the components. Obtain the wattage information for the components from the manufacturer's documentation. When deciding on a power supply, make sure to choose a power supply that has more than enough power for the current components. CAUTION: Do not open a power supply. Electronic capacitors located inside of a power supply, shown in Figure below, can hold a charge for extended periods of time. MOTHERBOARD The motherboard is the main printed circuit board and contains the buses, or electrical pathways, found in a computer. These buses allow data to travel between the various components that comprise a computer. A motherboard is also known as the system board, the backplane, or the main board. The motherboard accommodates the central processing unit (CPU), RAM, expansion slots, heat sink/fan assembly, BIOS chip, chip set, and the embedded wires that interconnect the motherboard components. Sockets, internal and external connectors, and various ports are also placed on the motherboard. The form factor of motherboards pertains to the size and shape of the board. It also describes the physical layout of the different components and devices on the motherboard. Example of Form factors: Advanced Technology(AT), Advanced Technology Extended(ATX), Balanced Technology Extended (BTX), Low Profile Extended(LPX), mini ATX, Micro ATX chip set: An important set of components on the motherboard is the chip set. The chip set is composed of various integrated circuits attached to the motherboard that control how system hardware interacts with the CPU and motherboard. The CPU is installed into a slot or socket on the motherboard. The socket on the motherboard determines the type of CPU that can be installed. The chip set of a motherboard allows the CPU to communicate and interact with the other components of the computer, and to exchange data with system memory, or RAM, hard disk drives, video cards, and other output devices. The chip set establishes how much memory can be added to a motherboard. The chip set also determines the type of connectors on the motherboard. Most chip sets are divided into two distinct components, Northbridge and Southbridge. What each component does varies from manufacturer to manufacturer, but in general the Northbridge controls access to the RAM, video card, and the speeds at which the CPU can communicate with them. The video card is sometimes integrated into the Northbridge. The Southbridge, in most cases, allows the CPU to communicate with the hard drives, sound card, USB ports, and other I/O ports. CENTRAL PROCESSING UNIT (CPU) The central processing unit (CPU) is considered the brain of the computer. It is sometimes referred to as the processor. Most calculations take place in the CPU. In terms of computing power, the CPU is the most important element of a computer system. CPUs come in different form factors, each style requiring a particular slot or socket on the motherboard. Common CPU manufacturers include Intel and AMD. The CPU executes a program, which is a sequence of stored instructions. Each model of processor has an instruction set, which it executes. The CPU executes the program by processing each piece of data as directed by the program and the instruction set. While the CPU is executing one step of the program, the remaining instructions and the data are stored nearby in a special memory called cache. The power of a CPU is measured by the speed and the amount of data that it can process. The speed of a CPU is rated in cycles per second. The speed of current CPUs is measured in millions of cycles per second, called megahertz (MHz), or billions of cycles per second, called gigahertz (GHz). The amount of data that a CPU can process at the one time depends on the size of the processor data bus. This is also called the CPU bus or the front side bus (FSB). The wider the processor data bus width, the more powerful the processor is. Current processors have a 32-bit or a 64-bit processor data bus. The latest processor technology has resulted in CPU manufacturers finding ways to incorporate more than one CPU core onto a single chip. Many CPUs are capable of processing multiple instructions concurrently: • Single Core CPU – One core inside a single CPU chip that handles all of the processing capability. A motherboard manufacturer may provide sockets for more than one single processor, providing the ability to build a powerful, multi-processor computer. • Dual Core CPU – Two cores inside a single CPU chip in which both cores can process information at the same time. Fan Electronic components generate heat. Heat is caused by the flow of current within the components. Computer components perform better when kept cool. If the heat is not removed, the computer may run slower. If too much heat builds up, computer components can be damaged. Increasing the air flow in the computer case allows more heat to be removed. A case fan, shown below, is installed in the computer case to make the cooling process more efficient. In addition to case fans, a heat sink draws heat away from the core of the CPU. A fan on top of the heat sink, shown in below, moves the heat away from the CPU. Other components are also susceptible to heat damage and are sometimes equipped with fans. Video adapter cards also produce a great deal of heat. Fans are dedicated to cool the graphics-processing unit (GPU), as seen in Figure below. Computers with extremely fast CPUs and GPUs may use a water-cooling system. A metal plate is placed over the processor and water is pumped over the top to collect the heat that the CPU creates. The water is pumped to a radiator to be cooled by the air, and then re-circulated. ROM Read-only memory (ROM) chips are located on the motherboard. ROM chips contain instructions that can be directly accessed by the CPU. Basic instructions for booting the computer and loading the operating system are stored in ROM. ROM chips retain their contents even when the computer is powered down. The contents cannot be erased or changed by normal means. The different types of ROM are: • Read-Only Memory chip (ROM) • Programmable Read-Only Memory chip (PROM) • Erasable Programmable Read-Only Memory chip (EPROM) • Electrically Erasable Programmable Read-Only Memory chip (EEPROM) RAM Random access memory (RAM) is the temporary storage for data and programs that are being accessed by the CPU. RAM is volatile memory, which means that the contents are erased when the computer is powered off. The more RAM in a computer, the more capacity the computer has to hold and process large programs and files, as well as enhance system performance. RAM Types: • Dynamic RAM (DRAM) • Static RAM (SRAM) • Fast Page Mode DRAM (FPM memory) • Extended Data Out RAM (EDO memory) • Synchronous DRAM (SDRAM) • Double Data Rate SDRAM (DDR SDRAM) • Double Data Rate 2 SDRAM (DDR2 SDRAM) Adapter cards Adapter cards increase the functionality of a computer by adding controllers for specific devices or by replacing malfunctioning ports. Figure 1 shows several types of adapter cards. Adapter cards are used to expand and customize the capability of the computer: • NIC – Connects a computer to a network using a network cable • Wireless NIC – Connects a computer to a network using radio frequencies • Sound adapter – Provides audio capability • Video adapter – Provides graphic capability • Modem adapter – Connects a computer to the Internet using a phone line • SCSI adapter – Connects SCSI devices, such as hard drives or tape drives, to a computer • RAID adapter – Connects multiple hard drives to a computer to provide redundancy and to improve performance • USB port – Connects a computer to peripheral devices • Parallel port – Connects a computer to peripheral devices • Serial port – Connects a computer to peripheral devices Computers have expansion slots on the motherboard to install adapter cards. The type of adapter card connector must match the expansion slot STORAGE DRIVE A storage drive reads or writes information to magnetic or optical storage media. The drive can be used to store data permanently or to retrieve information from a media disk. Storage drives can be installed inside the computer case, such as a hard drive. For portability, some storage drives can connect to the computer using a USB port, a FireWire port, or an SCSI port. These portable storage drives are sometimes referred to as removable drives and can be used on multiple computers. Here are some common types of storage drives: • Floppy drive • Hard drive • Optical drive • Flash drive • Network drive Floppy Drive A floppy drive, or floppy disk drive, is a storage device that uses removable 3.5-inch floppy disks. These magnetic floppy disks can store 720 KB or 1.44 MB of data. In a computer, the floppy drive is usually configured as the A: drive. The floppy drive can be used to boot the computer if it contains a bootable floppy disk. A 5.25-inch floppy drive is older technology and is seldom used. Hard Drive A hard drive, or hard disk drive, is a magnetic storage device that is installed inside the computer. The hard drive is used as permanent storage for data. In a computer, the hard drive is usually configured as the C: drive and contains the operating system and applications. The hard drive is usually configured as the first drive in the boot sequence. The storage capacity of a hard drive is measured in billions of bytes, or gigabytes (GB). The speed of a hard drive is measured in revolutions per minute (RPM). Multiple hard drives can be added to increase storage capacity. Optical Drive An optical drive is a storage device that uses lasers to read data on the optical media. There are two types of optical drives: • Compact disc (CD) • Digital versatile disc (DVD) CD and DVD media can be pre-recorded (read-only), recordable (write once), or re-recordable (read and write multiple times). CDs have a data storage capacity of approximately 700 MB. DVDs have a data storage capacity of approximately 8.5 GB on one side of the disc. There are several types of optical media: • CD-ROM – CD read-only memory media that is pre-recorded. • CD-R –CD-recordable media that can be recorded once. • CD-RW – CD-rewritable media that can be recorded, erased, and re-recorded. • DVD-ROM – DVD read-only memory media that is pre-recorded. • DVD-RAM – DVD-random access memory media that can be recorded, erased, and re-recorded. • DVD+/-R – DVD-recordable media that can be recorded once. • DVD+/-RW – DVD-rewritable media that can be recorded, erased, and re-recorded. Flash Drive A flash drive, also known as a thumb drive, is a removable storage device that connects to a USB port. A flash drive uses a special type of memory that requires no power to maintain the data. These drives can be accessed by the operating system in the same way other types of drives are accessed. Types of Drive Interfaces Hard drives and optical drives are manufactured with different interfaces that are used to connect the drive to the computer. To install a storage drive in a computer, the connection interface on the drive must be the same as the controller on the motherboard. Here are some common drive interfaces: • IDE – Integrated Drive Electronics, also called Advanced Technology Attachment (ATA) is an early drive controller interface that connects computers and hard disk drives. An IDE interface uses a 40-pin connector. • EIDE – Enhanced Integrated Drive Electronics, also called ATA-2, is an updated version of the IDE drive controller interface. EIDE supports hard drives larger than 512 MB, enables Direct Memory Access (DMA) for speed, and uses the AT Attachment Packet Interface (ATAPI) to accommodate optical drives and tape drives on the EIDE bus. An EIDE interface uses a 40-pin connector. • PATA – Parallel ATA refers to the parallel version of the ATA drive controller interface. • SATA – Serial ATA refers to the serial version of the ATA drive controller interface. A SATA interface uses a 7-pin connector. • SCSI – Small Computer System Interface is a drive controller interface that can connect up to 15 drives. SCSI can connect both internal and external drives. An SCSI interface uses a 50-pin, 68-pin, or 80-pin connector. CHARACTERISTICS OF PORTS AND CABLES Internal PC Cables Drives require both a power cable and a data cable. A power supply will have a SATA power connector for SATA drives, a Molex power connector for PATA drives, and a Berg 4-pin connector for floppy drives. The buttons and the LED lights on the front of the case connect to the motherboard with the front panel cables. Data cables connect drives to the drive controller, which is located on an adapter card or on the motherboard. Here are some common types of data cables: • Floppy disk drive (FDD) data cable – Data cable has up to two 34-pin drive connectors and one 34-pin connector for the drive controller. • PATA(IDE/EIDE) 40-conductor data cable - Originally, the IDE interface supported two devices on a single controller. With the introduction of Extended IDE, two controllers capable of supporting two devices each were introduced. 40-pin connectors are used on 40-conductor ribbon cable. The cable has two connectors for the drives and a third for the controller. • PATA (EIDE) 80-conductor cable - As the data rates available over the EIDE interface increased, the chances of corruption of the data being transmitted increased. the use of 80-conductor cable was introduced for devices transmitting at 33.3MBps and over, allowing for a more reliable balanced data transmission. The connectors are still of the 40-pin variety. • SATA data cable – Serial ATA data cable has seven conductors, one keyed connector for the drive, and one keyed connector the drive controller. • SCSI data cable – There are three types of SCSI data cables. A narrow SCSI data cable has 50-conductors, up to seven 50-pin connectors for drives, and one 50-pin connector for the drive controller, also called the host adapter. A wide SCSI data cable has 68-conductors, up to fifteen 68-pin connectors for drives, and one 68-pin connector for the host adapter. An Alt-4 SCSI data cable has 80-conductors, up to "15" 80-pin connectors for drives, and one 80-pin connector for the host adapter. NOTE: A colored stripe on a cable identifies Pin 1 on the cable. When installing a data cable, always ensure that Pin 1 on the cable aligns with Pin 1 on the drive or drive controller. Some cables may be keyed and therefore they can only be connected one way to the drive and drive controller. Input/output (I/O) ports Input/output (I/O) ports on a computer connect peripheral devices, such as printers, scanners, and portable drives. The following ports and cables are commonly used: • Serial Ports and Cables A serial port can be either a DB-9, as shown in Figure below, or a DB-25 male connector. Serial ports transmit one bit of data at a time. To connect a serial device, such as a modem or printer, a serial cable must be used. A serial cable has a maximum length of 50 feet (15.2 m). • USB Ports and Cables The Universal Serial Bus (USB) is a standard interface that connects peripheral devices to a computer. It was originally designed to replace serial and parallel connections. USB devices are hot-swappable, which means that users can connect and disconnect the devices while the computer is powered on. USB connections can be found on computers, cameras, printers, scanners, storage devices, and many other electronic devices. A USB hub is used to connect multiple USB devices. A single USB port in a computer can support up to 127 separate devices with the use of multiple USB hubs. Some devices can also be powered through the USB port, eliminating the need for an external power source. Figure below shows USB cables with connectors. USB 1.1 allowed transmission rates of up to 12 Mbps in full-speed mode and 1.5 Mbps in low speed mode. USB 2.0 allows transmission speeds up to 480 Mbps. USB devices can only transfer data up to the maximum speed allowed by the specific port. • FireWire Ports and Cables FireWire is a high-speed, hot-swappable interface that connects peripheral devices to a computer. A single FireWire port in a computer can support up to 63 devices. Some devices can also be powered through the FireWire port, eliminating the need for an external power source. FireWire uses the IEEE 1394 standard and is also known as i.Link. The IEEE 1394a standard supports data rates up to 400 Mbps and cable lengths up to 15 feet (4.5 m). This standard uses a 6-pin connector or a 4-pin connector • Parallel Ports and Cables A parallel port on a computer is a standard Type A DB-25 female connector. The parallel connector on a printer is a standard Type B 36-pin Centronics connector. Some newer printers may use a Type C high-density 36-pin connector. Parallel ports can transmit 8 bits of data at one time and use the IEEE 1284 standard. To connect a parallel device, such as a printer, a parallel cable must be used. A parallel cable, as shown in Figure below, has a maximum length of 15 feet (4.5 m). • SCSI Ports and Cables A SCSI port can transmit parallel data at rates in excess of 320 Mbps and can support up to 15 devices. If a single SCSI device is connected to an SCSI port, the cable can be up to 80 feet (24.4 m) in length. If multiple SCSI devices are connected to an SCSI port, the cable can be up to 40 (12.2 m) feet in length. An SCSI port on a computer can be one of three different types, as shown in Figure below: 50, 68 and 80 pin connectors • Network Ports and Cables A network port, also known as an RJ-45 port, connects a computer to a network. The connection speed depends on the type of network port. Standard Ethernet can transmit up to 10 Mbps, Fast Ethernet can transmit up to 100 Mbps, and Gigabit Ethernet can transmit up to 1000 Mbps. The maximum length of network cable is 328 feet (100 m). A network connector is shown in Figure below. • PS/2 Ports A PS/2 port connects a keyboard or a mouse to a computer. The PS/2 port is a 6-pin mini-DIN female connector. The connectors for the keyboard and mouse are often colored differently, as shown in Figure below. If the ports are not color-coded, look for a small figure of a mouse or keyboard next to each port. • Audio Ports An audio port connects audio devices to the computer. The following audio ports are commonly used, as shown in Figure below: • Line In – Connects to an external source, such as a stereo system • Microphone – Connects to a microphone • Line Out – Connects to speakers or headphones • Gameport/MIDI – Connects to a joystick or MIDI-interfaced device • Video Ports and Connectors A video port connects a monitor cable to a computer. Figure below shows two of the most common video ports. There are several video port and connector types: • Video Graphics Array (VGA) – VGA has a 3-row 15-pin female connector and provides analog output to a monitor. • Digital Visual Interface (DVI) – DVI has a 24-pin female connector or a 29-pin female connector and provides a compressed digital output to a monitor. DVI-I provides both analog and digital signals. DVI-D provides digital signals only. • High-Definition Multimedia Interface (HDMi) – HDMi has a 19-pin connector and provides digital video and digital audio signals. • S-Video – S-Video has a 4-pin connector and provides analog video signals. • Component/RGB – RGB has three shielded cables (red, green, blue) with RCA jacks and provides analog video signals. INPUT DEVICES An input device is used to enter data or instructions into a computer. Here are some examples of input devices: • Mouse and keyboard • Digital camera and digital video camera • Biometric authentication device • Touch screen • Scanner The mouse and keyboard are the two most commonly used input devices. The mouse is used to navigate the graphical user interface (GUI). The keyboard is used to enter text commands that control the computer. Like the keyboard on a typewriter, it has keys for letters and numbers, but it also has special keys: • The function keys, found on the top row, perform different functions depending on where they are used. • The numeric keypad, located on the right side of most keyboards, allows you to enter numbers quickly. • The navigation keys, such as the arrow keys, allow you to move your position within a document or webpage. Digital cameras and digital video cameras, shown in Figure below, create images that can be stored on magnetic media. The image is stored as a file that can be displayed, printed, or altered. Biometric identification makes use of features that are unique to an individual user, such as fingerprints, voice recognition, or a retinal scan. When combined with ordinary usernames, biometrics guarantees that the authorized person is accessing the data. Figure below shows a laptop that has a built-in fingerprint scanner. A touch screen has a pressure-sensitive transparent panel. The computer receives instructions specific to the place on the screen that the user touches. A scanner digitizes an image or document. The digitization of the image is stored as a file that can be displayed, printed, or altered. A bar code reader is a type of scanner that reads Universal Product Code (UPC) bar codes. It is widely used for pricing and inventory information. OUTPUT DEVICES An output device is used to present information to the user from a computer. Here are some examples of output devices: • Monitors and projectors • Printers, scanners, and fax machines • Speakers and headphones Monitors and Projectors Monitors and projectors are primary output devices for a computer. There are different types of monitors, as shown in Figure below. The most important difference between these monitor types is the technology used to create an image: • CRT – Cathode-ray tube monitor is the most common monitor type. There are three electron beams. Each focused to hit colored phosphor on the screen which will glow red, blue or green. Areas not struck by the electron beam do not glow. The combination of glowing and non-glowing areas is what creates the image on the screen. Most televisions also use this technology. • LCD – Liquid crystal display is commonly used in laptops and some projectors. It consists of two polarizing filters with a liquid crystal solution between them. An electronic current aligns the crystals so that light can either pass through or not pass through. The effect of light passing through in certain areas and not in others is what creates the image. LCD comes in two forms, active matrix and passive matrix. Active matrix is sometimes called thin film transistor (TFT). TFT allows each pixel to be controlled, which creates very sharp color images. Passive matrix is less expensive than active matrix but does not provide the same level of image control. • DLP – Digital light processing is another technology used in projectors. DLP projectors use a spinning color wheel with a microprocessor-controlled array of mirrors called a digital micro mirror device (DMD). Each mirror corresponds to a specific pixel. Each mirror reflects light toward or away from the projector optics. This creates a monochromatic image of up to 1024 shades of gray in between white and black. The color wheel then adds the color data to complete the projected, color image. Monitor resolution refers to the level of image detail that can be reproduced. Higher resolution settings produce better image quality. There are several factors involved in monitor resolution: • Pixels – The term pixel is an abbreviation for picture element. Pixels are the tiny dots that comprise a screen. Each pixel consists of red, green, and blue. • Dot Pitch – Dot pitch is the distance between pixels on the screen. A lower dot pitch number produces a better image. • Refresh Rate – The refresh rate is how often per second the image is rebuilt. A higher refresh rate produces a better image and reduces the level of flicker. • Interlace/Non-Interlace – Interlaced monitors create the image by scanning the screen two times. The first scan covers the odd lines, top to bottom, and the second scan covers the even lines. Non-interlaced monitors create the image by scanning the screen, one line at a time from top to bottom. Most CRT monitors today are non-interlaced. • Horizontal Vertical Colors (HVC) – The number of pixels in a line is the horizontal resolution. The number of lines in a screen is the vertical resolution. The number of colors that can be reproduced is the color resolution. Aspect Ratio – Aspect ratio is the horizontal to vertical measurement of the viewing area of a monitor. For example, a 4:3 aspect ratio would apply to a viewing area that is 16 inches wide by 12 inches high. A 4:3 aspect radio would also apply to a viewing area that is 24 inches wide by 18 inches high. A viewing area that is 22 inches wide by 12 inches high has an aspect ratio of 11:6. Monitors have controls for adjusting the quality of the image. Here are some common monitor settings: • Brightness – Intensity of the image • Contrast – Ratio of light to dark • Position – Vertical and horizontal location of image on the screen • Reset – Returns the monitor settings to factory settings Printers, Scanners, and Fax Machines Printers are output devices that create hard copies of computer files. Some printers specialize in particular applications, such as printing color photographs. Other all-in-one type printers, like the one shown in Figure below, are designed to provide multiple services such as printing, fax, and copier functions. Speakers and Headphones Speakers and headphones are output devices for audio signals. Most computers have audio support either integrated into the motherboard or on an adapter card. Audio support includes ports that allow input and output of audio signals. The audio card has an amplifier to power headphones and external speakers, which are shown in Figure below. Computer Peripherals Computer peripherals are any electronic devices that can be hooked up to a computer other than the standard input-output devices (monitor, keyboard,mouse). Peripheral devices include speakers, microphones, printers, scanners, digital cameras, plotters, and modems. Peripherals often require special software packages called "drivers". These drivers are usually included with the peripheral at purchase time.