Read an Excerpt
From Chapter 2: PC Components, Features, and System Design
...A modern PC is both simple and complicated. It is simple in the sense that over the years many of the components used to construct a system have become integrated with other components into fewer and fewer actual parts. It is complicated in the sense that each part in a modern system performs many more functions than the same types of parts in older systems.
In this section, we briefly examine all the components in a modern PC system. Each of these components will be expanded on in later chapters.
Here are the components needed to assemble a basic modern PC system:
- Memory (RAM)
- Case (chassis)
- Power supply
- Floppy drive
- Hard disk
- CD-ROM drive
- Video card
- Monitor (display)
- Sound card
The motherboard is the core of the system. It really is the PC, everything else is connected to it, and it controls everything in the system. Motherboards are available in several different shapes or form factors. The motherboard usually contains the following individual components:
- Processor socket (or slot)
- Processor voltage regulators
- Motherboard chipset
- Level 2 cache
- Memory SIMM or DIMM sockets
- Bus slots
- ROM BIOS
- Clock/CMOS battery
- Super I/O chip
The processor is often thought of as the "engine" of the computer. A sophisticated piece of miniaturized electronics with millions of transistors, the processor (often called the CPU or Central Processing Unit) is like the conductor in an orchestra. The processor reads program instructions (commands) from memory that tell it what it needs to do to accomplish the work that the user wants, and then executes them. The processor has the distinction of being one of the most expensive parts of most computers, even though it is also one of the smallest parts.
Microprocessors are covered in detail in Chapter 3, "Microprocessor Types and Specifications."
The system memory is often called RAM for Random Access Memory. This is the primary memory that holds all the programs and data the processor is using at a given time. RAM requires power to maintain storage, so when you turn off the computer everything in RAM is cleared, and when you turn it back on the memory must be reloaded with programs for the processor to run. The initial programs for the processor come from a special type of memory called ROM (Read Only Memory), which cannot normally be erased. This contains instructions to get the system to load an operating system and other programs from one of the disk drives into the main memory so that the system can be running normally and perform useful work. Newer operating systems allow several programs to run at one time, with each program or data file loaded using some of the memory. Generally, the more memory your system has, the more programs you can run simultaneously.
Memory is normally purchased and installed in a modern system in SIMM (Single Inline Memory Module) or DIMM (Dual Inline Memory Module) form. Formerly very expensive, more recently memory prices have dropped, significantly reducing the cost of memory as compared to other parts of the system. Even so, the cost of the recommended amount of memory for a given system is usually equal or greater than that of the motherboard.
Memory is covered in detail in Chapter 5, "Memory."
The box or outer shell that houses most of the computer, the case is one of the least emphasized and most overlooked parts of the PC. Although it may seem only cosmetic, the case actually performs several important functions for your PC, including protection for the system components, directing cooling airflow, and allowing installation of and access to the system components. The case often includes a matching power supply, and must also be designed with the form factor of the motherboard and other system components in mind.
The case is covered in detail in Chapter 6, "Power Supply and Case."
The power supply is what feeds electrical power to every single part in the PC. As such it has a very important job, yet it is one of the least glamorous parts of the system, so it receives little attention. Unfortunately, this often means it is one of the components that is most skimped on when constructing a system. The main function of the supply is to convert the 110v AC wall current into the 3.3v, 5v, and l2fv power that the system requires for operation.
The power supply is covered in detail in Chapter 6.
Floppy Disk Drive
Floppy disks are the smallest and slowest form of offline storage. Floppy disks provide a simple, convenient way to transfer information, install new software, and back up small amounts of files. With the advent of CD-ROM discs as the primary method of installing or loading new software in a system, the floppy drive component is not as important as it was years ago. Even so, virtually all PCs made in the last 10 years use a standard 3 1/2 inch, 1.44M capacity floppy drive. Recently some advancements have created floppy drives with up to 120 M or more of storage, but these have yet to fully catch on as a standard PC component.
Floppy disk drives are covered in detail in Chapter 12, "Magnetic Storage."
Hard Disk Drive
The hard disk is the primary archival storage memory for the system. It is used to contain copies of all programs and data not currently active in main memory. A hard drive is so named because it consists of spinning platters of aluminum or ceramic that are coated with a magnetic media. The platters come in various sizes, and by the density, size, and number of platters, hard drives can be created with many different storage capacities. Most desktop systems today use drives with 3 1/2-inch platters, while most laptop or notebook computers use 2 1/2-inch platter drives.
Hard disk drives are also covered in detail in Chapter 12.
CD-ROM stands for Compact Disk-Read Only Memory. As the name implies, CD-ROM drives use small discs, identical to the ones that hold music, to hold computer information. Also as the name implies, they are a read-only medium. You can read information from them but not write to them (except for some special exceptions). CD-ROMs are currently the most popular way that computer companies distribute applications and games, and are ideal for multimedia information such as videos, music, and large graphics files.
CD-ROM drives are covered in detail in Chapter 13, "Optical Storage."
The keyboard is the main input device for most computers. It is used to input text or enter commands into the PC. Keyboards are pretty much standard affairs these days, although they can vary greatly in quality and some may have additional features.
Keyboards are covered in detail in Chapter 7, "Input Devices."
Until the invention of the Graphical User Interface (GUI), the keyboard was the only way that most people input information into their PCs. The mouse is used in graphical environments to let users provide simple 'point and click' instructions to the computer. The main advantage of a mouse over the keyboard is simplicity. There are many operations that are much easier to perform with a mouse than a keyboard (such as picking an item on a screen or choosing from a list of options).
The mouse is covered in detail in Chapter 7.
The video card controls the information you see on the monitor. All video cards have four basic parts-a video chip or chipset, Video RAM, a DAC (Digital to Analog Converter), and a BIOS. The video chip is what actually controls the information on the screen by writing data to the video RAM. The DAC reads the video RAM and converts the digital data there into analog signals to drive the monitor. The BIOS holds the primary video driver that allows the display to function during boot time and at a DOS prompt in basic text mode. More enhanced drivers are then usually loaded from disk to enable advanced video modes for Windows or applications software.
Video cards are covered in detail in Chapter 8, "Video Hardware."
The monitor is a specialized, high-resolution screen, similar to a high-quality television. The video card sends the contents of its video memory out to your monitor normally at a rate of 60 or more times per second. The actual display screen is made up of red, green, and blue dots that are illuminated by an electron beam from behind. The video card DAC chip controls the sweep of the electron beam, which then controls what dots are lit up and how bright they are, which then determines the picture you see on the screen.
Monitors are covered in detail in Chapter 8...