1.1. Hardware
Hardware refers to all the pieces of physical equipment that make up a computer system. The computer hardware you are most familiar with is probably the personal computer or PC.
A PC includes several pieces of hardware or devices.
The power supply is a device that distributes electricity to the various components of the system. The electrical cord runs from the power supply to the electrical outlet. The power supply also includes a fan that cools the internal components.
The motherboard is the largest circuit board inside your personal computer. It contains millions of electronic components on silicon chips. These chips store programmed instructions in active memory (see next page for RAM). They also execute the instructions stored in other chips. The motherboard has expansion sockets or slots (known as the bus, see next page). These slots enable the installation of add-on boards.
The motherboard has some specialty ROM (Read-Only Memory) chips that contain the BIOS (Basic Input/Output System). The BIOS checks your computer’s components and causes the operating system to start.
To work properly, the BIOS needs to know the configuration of your computer’s hardware. This hardware information is stored in the CMOS (Complementary Metal Oxide Semiconductor) — a chip with configuration controlled by the setup program. The CMOS provides information on the following components:
- system date and time,
- mouse,
- keyboard,
- hard drive (number and capacity of the drives),
- DVD±R/RW drive.
The settings are permanently saved in a 64-byte piece of CMOS. A small battery supplies the CMOS power; therefore, its contents are not lost when the PC is turned off.
The CPU (Central Processing Unit) is a chip located on the motherboard which performs mathematical calculations and logic functions (determining if one value is greater than another, and so on). The CPU is often referred to as the brain of a computer since it administers the functions of the other components. When the users say their machine has a Core 2 Duo processor, they are talking about the CPU chip.
The bus is the main communication path, or series of paths, on the motherboard that connects the system’s components with the CPU. The bus also connects external components via expansion slots. These slots may contain plug-in cards that let the computer communicate with other devices, such as monitors and printers.
RAM (Random Access Memory), special chips connected to the CPU, is the area where programs and data are found while in use. When you run an application (Microsoft Word, for example), the computer stores the program in RAM. If you then open the document, the machine will also upload it into RAM. When you save the document, the CPU copies it from RAM to the persistent store. When you close the document, the CPU deallocates the memory that was captured. When you close the program down, the storage is also released. RAM holds data only until the power is off. At shut down or power loss, information in RAM is lost. Hence, any changes not saved before the machine is switched off cannot be restored. In modern PCs, RAM capacity is measured in gigabytes. In general, the more RAM your computer has, the better it is capable of running programs that require processing power.
A peripheral is a device plugged into the computer via the bus. Many major components of a PC system are peripherals including monitors, keyboards, and disk drives. Printers and scanners are also peripherals.
Some peripherals because of their small size or delicate nature are mounted directly inside the computer case. Video boards, internal modems, and sound cards are devices inside the computer that depend on the bus.
Peripherals are often divided into two categories — input devices and output devices. Some peripherals serve as both input and output devices; for this reason, the categories are not exclusive. Some common peripherals and their functions are described below.
The monitor is an output device that displays input and the results of processing. Most monitors on PCs and laptops use liquid crystal display (LCD) technology, similar to that applied in some television sets. In fact, some computers use TV sets as monitors.
The mouse is an input device that you use to control a pointer displayed on the monitor. There is a wide variety of mouse pointing devices. Some are moved over a surface and may be wireless; some let you use your thumb or fingers to roll a ball that moves the pointer; others, especially on laptop computers, operate when you drag your finger across a small screen called a touch pad.
The keyboard is an input device with alphabetic, numeric, and function keys with the standard layout. Some keyboards rearrange particular keys and have keys that other keyboards may be missing. The special keys (such as Fn (Function), Ctrl (Control), and Alt keys) are used either separately or in combination to cause programs to perform actions.
Most computers contain a hard disk (or hard drive) and optical drive, such as a DVD drive. DVDs can be removed and carried over from one place to another; hard disks are installed inside the computer and are not considered portable. Disk drives are identified by a letter. The typical personal computer has an optical drive identified as D:. It probably also has a hard drive known as C:. Hard disks, DVDs, and drives are both input and output devices.
Modems and other telecommunication facilities (when used with appropriate software) serve as sources of both input and output. Telecommunication gives you access to the world outside your personal computer — to such services as MSN and that vast network of computers known as the Internet or World Wide Web. A modem is installed inside the computer case (an internal modem), or it is connected via a communications port (an external modem).