How Are Various Styles of System Units Different?

The system unit is a case that contains electronic components of the computer used to process data. On desktop personal computers, most storage devices also are part of the system unit. On notebook computers, the keyboard and pointing device often occupy the area on top of the system unit, and the display attaches to the system unit by hinges. On mobile devices, the display frequently is part of the system unit.

What Are Chips, Adapter Cards, and Other Components of the Motherboard?

The motherboard is the main circuit board of the system unit. The motherboard contains many electronic components including a processor chip, memory chips, expansion slots, and adapter cards. A chip is a small piece of semiconducting material, usually silicon, on which integrated circuits are etched. Expansion slots hold adapter cards that provide connections and functions not built into the motherboard.

What Are the Components of a Processor and How Do They Complete a Machine Cycle?

The processor interprets and carries out the basic instructions that operate a computer. Processors contain a control unit that directs and coordinates most of the operations in the computer and an arithmetic logic unit (ALU) that performs arithmetic, comparison, and logical operations. The machine cycle is a set of four basic operations — fetching, decoding, executing, and storing — that the processor repeats for every instruction. The control unit fetches program instructions and data from memory and decodes the instructions into commands the computer can execute. The ALU executes the commands, and the results are stored in memory.

What Are the Characteristics of Various Personal Computer Processors?

Intel produces the Pentium processor for high-performance PCs, the Celeron processor for basic PCs, and the Xeon and Itanium processors for workstations and low-end servers. AMD manufactures Intel-compatible processors, which have a similar internal design as Intel processors. Motorola produces the Motorola processor, with a design different from the Intel-style processor, for Apple computers. Some devices have a system on a chip processor that integrates the functions of a processor, memory, and a video card on a single chip.

What Is a Bit and How Does a Series of Bits Represent Data?

Most computers are digital and recognize only two discrete states: off and on. To represent these states, computers use the binary system, which is a number system that has just two unique digits — 0 (for off) and 1 (for on) — called bits. A bit is the smallest unit of data a computer can process. Grouped together as a unit, 8 bits form a byte, which provides enough different combinations of 0s and 1s to represent 256 individual characters. The combinations are defined by patterns, called coding schemes, such as ASCII, EBCDIC, and Unicode .

How Do Programs Transfer In and Out of Memory?

When an application program starts, the program’s instructions load into memory from the hard disk. The program and operating system instructions are in memory and the program’s window is displayed on the screen. When you quit the program, the program instructions are removed from memory and the program no longer is displayed on the screen.

What Are the Various Types of Memory?

The system unit contains volatile and nonvolatile memory. Volatile memory loses its contents when the computer’s power is turned off.

Nonvolatile memory does not lose its contents when the computer’s power is turned off. RAM is the most common type of volatile memory. ROM, flash memory, and CMOS are examples of nonvolatile memory. RAM consists of memory chips that can be read from and written to by the processor and other devices. ROM refers to memory chips storing permanent data and instructions that usually cannot be modified. Flash memory can be erased electronically and rewritten. CMOS technology uses battery power to retain information even when the power to the computer is turned off.

What Are the Types of Expansion Slots and Adapter Cards?

An expansion slot is a socket on a motherboard that can hold an adapter card. An adapter card is a circuit board that enhances functions of a component of the system unit and/or provides a connection to a peripheral such as a modem, disk drive, printer, scanner, or keyboard. Several types of adapter cards exist. A sound card enhances the sound-generating capabilities of a personal computer. A video card converts computer output into a video signal that displays an image on the screen. A modem card enables computers to communicate. A network card allows a computer to access a network.

How Are a Serial Port, a Parallel Port, a USB Port, and Other Ports Different?

A port is the point at which a peripheral attaches to a system unit so it can send data to or receive information from the computer. A serial port, which transmits data 1 bit at a time, usually connects devices that do not require fast data transmission , such as a mouse, keyboard, or modem. A parallel port, which transfers more than 1 bit at a time, often connects a printer to the system unit. A USB port can connect up to 127 different peripherals together with a single connector type. Five special-purpose ports are FireWire, MIDI, SCSI, IrDA, and Bluetooth. A FireWire port can connect multiple types of devices that require faster data transmission speeds. A MIDI port connects the system unit to a musical instrument. A SCSI port attaches the system unit to SCSI peripherals, such as disk drives. An IrDA port and Bluetooth technology allow wireless devices to transmit signals to a computer via infrared light waves or radio waves.

How Do Buses Contribute to a Computer’s Processing Speed?

A bus is an electrical channel along which bits transfer within the circuitry of a computer, allowing devices both inside and attached to the system unit to communicate. The size of a bus, called the bus width , determines the number of bits that the computer can transmit at one time. The larger the bus width, the faster the computer transfers data.

What Are the Components in Mobile Computers and Mobile Devices?

In addition to the motherboard, processor, memory, sound card, PC Card slot, and drive bay , a mobile computer’s system unit also houses devices such as the keyboard, pointing device, speakers, and display. The system unit for a typical notebook computer often has parallel, serial, video, USB, speaker, microphone, and keyboard/mouse ports. Tablet PCs usually include several slots and ports. PDAs often have an IrDA port or are Bluetooth enabled so users can communicate wirelessly.