The CPU is the brain of the computer, responsible for controlling the internal workings of the machine. It is made up of circuitry, or electronic components wired together to control the flow of electrical signals. The CPU is by far the most complex part of a computer system. Common CPUs include the Intel Pentium 4, AMD AthlonTM, and Motorola PowerPCTM G4. In controlling the workings of the computer, the CPU has two key tasks: (1) fetching programs instructions from memory, and (2) executing those instructions. CPUs can process instruction sequences extremely quickly, which enables the processors to handle these immense programs. CPU speed is generally measured in gigahertz (GHz), which indicates how many billions of instructions a CPU can execute in a second.-
Memory is the part of the computer that stores programs and data. Memory is commonly divided into (1) main or primary memory (consisting of RAM and cache) which is fast, volatile and expensive, and (2) secondary memory (such as hard disk and CD-ROM) which is slow but permanent and inexpensive.
Input devices allow the computer to receive data and instructions from an external source, such as a person entering commands at a keyboard. Examples of input devices are keyboards, mice track pads, microphones and scanners. On the other hand, output devices allow the computer to display or broadcast its results. Examples of output devices are monitors, printers, and speakers. Devices that enable computer to communicate with other computers are both input and output devices. Examples include modems, and wireless networking adapters.
A hard disk is a metal platter that stores bits as magnetized and nonmagnetized spots. The disk rotates under a sensor, which detects the magnetized spots and interprets them as bits. A hard disk is capable of permanently storing vast amounts of information (usually measured in gigabytes), which can be transferred in to main memory when needed. A floppy disk is a smaller, portable version of a hard disk, capable of storing up to 1.44MB of data on a 3.5-inch plastic disk. A CD (Compact Disk) is a metal disk that stores up to 700MB of data as patterns on its reflective surface. Using CD-ROM (Compact Disk-Read Only Memory) technology, the patterns are burned onto the surface of the disk with a laser and therefore cannot be overwritten. Using CD-RW (Compact Disk-ReWriteable) technology, patterns are formed in a photosensitive coating on the surface of the disk, allowing data to be overwritten repeatedly.
Software refers to the programs that execute on the hardware. A software program is a collection of instructions for the computer (more specifically, the CPU) to carry out in order to complete some tasks. For example, word processors such as Microsoft Word and Corel WordPerfect contain instructions for creating and managing documents; graphics programs such as Adobe and Macromedia Flash contain instructions for creating and displaying graphical images; and Web browsers such as Microsoft Internet Explorer and Netscape Navigator contain instructions for accessing and displaying web pages. Programs such as these are known as application software, each being designed to carry out tasks within a particular application area, such as word processing, graphical design, or Web access.
In contrast to application software, systems software manages the resources and behavior of the computer itself. The largest and most integral systems software stored on a computer is its operating system, a collection of programs that controls how the CPU, memory and I/O devices work together to execute programs. The most fundamental task performed by the operating system is to schedule the CPU�s operation, controlling how data and instructions are loaded from memory and accessed by the CPU.
CONTENTS