How Components Work Together

The diagram below summarizes how components introduced in this unit work together.

Figure 1 Overview of hardware components

The CPU executes instructions stored in memory devices. When the computer is being booted, the CPU fetches instructions from the permanent memory devices, ROM and CMOS. ROM is read-only memory that stores instructions needed to start up the computer. CMOS contains system configuration data. Once the computer is booted, RAM is used to load the rest of the instructions to be executed by the CPU. Data in RAM is temporary and will be lost when the computer is turned off.

Data from storage devices such as the CD-ROM drive and the hard drive are passed through the disk controller. Data can also be stored on hard disk or CD.

Data in the hardware system passes through buses. The buses are the communication channels among components in the system unit.

Peripheral devices such as the keyboard, mouse, joystick, printer, speakers, microphone, etc. are connected to the computer via ports typically in the back of a system unit. Graphics cards or sound cards are also examples of expansion cards that can be plugged into the expansion slot of the computer to extend or enhance the functionality of a computer.

When a computer processes requests from the user, the CPU directs the other components to carry out specific tasks, and data is passed among components through buses and the chipset. Use the diagram above as you follow through how data is transferred from component to component in the sample scenarios provided below:

To save a file to hard disk, the CPU would pass the data to be saved through the front bus to the chipset. The chipset sends the file data via the PCI bus to the disk controller, which would then send the data to the hard disk storage device.

To open and display an image file, the CPU would signal the disk controller to fetch the image file on the storage device and store it in RAM. The graphics card would then access the image data and display the image as pixels on the computer monitor.

These are generalizations for how components interact. When trying to understand a hardware system, keep in mind the general concepts of how components work together, and investigate the specifications of components to gain more precise understanding of how a given hardware system works. The exact nature of how each component works and interacts with other components is beyond the scope of this course.

2.4.2 Lab: Researching a Computer System

You can research a computer system using the Web by retrieving product reviews and price comparisons. Suppose you are interested in a particular line of notebook computers, such as the Dell Inspiron or the Sony VAIO. The following activity will lead you through a sample comparison.

2.4.3 Lab: Online Configuration

Some computer-vendor Web sites allow you to specify a system configuration by selecting from various menus listing available options. Then, when you click the "update price" button, you can see the exact price for the system you selected. Two such Web sites are Dell (www.dell.com) and Gateway, Inc. (www.gateway.com).