How It Works

How Does My Computer Work? Fire image.

When you type a letter or hit a key on the keyboard, a signal is sent to the Central Processing Unit (CPU). Each key on the keyboard has its own code that identifies which key was pressed. This is called ASCII code. The CPU is located on the main board of the computer, the "mother board". On the mother board are various daughter boards that perform various functions. The most common for basic computer use are the controller board, which controls the floppy and hard drives in your computer. Another necessary board is the video board that makes it possible to view the output of your computer. The computer memory is also located on the mother board. Other boards are also used, depending on how the user has set up their computer. One of the most common ones today is the sound card that enables the user to listen to sounds generated by the computer. As computers become more advanced, more of the daughter board functions are integrated into the mother board, making for fewer boards in the computer and for lower prices. The keyboard, mother board, CPU, memory and daughter boards are all interconnected by what is called a "bus," a group of common electrical connections or wires on the mother board. On the bus, data and signals are carried to all the devices such as drives, monitors, sound cards, etc. These signals and data streams are controlled by the CPU. Since all the devices are common, to prevent, for example, a signal to the disk drive from being sent to the monitor, a system of "interrupts" (IRQs) is used. An interrupt is a timing system designed to prevent the wrong component from getting the wrong signal. Every certain time interval, a different interrupt passes data or a signal, and each device takes its turn. All of this is controlled by the CPU from data via the Built In Operating System (BIOS) and happens too fast for the user to notice. When you type a command or click your mouse to load software, the CPU accepts the command through the BIOS on the mother board. The CPU then sends a command to the disk drive via the controller card to load the software into memory. Once the software is loaded, it tells the CPU what action to take in response to your keyboard or mouse commands. The results of these commands are seen on the monitor as they are generated by the software as it controls the CPU. The video board changes the signal to one that the monitor can use. Of course, the whole process is more complex and would take more space than we have here, but perhaps this brief explanation will help you gain a basic understanding about what happens inside the computer. Return to the PC Revolution Main Page