Inside a Computer: How A Personal Computer Works

Input & Output Devices

Bus - Bus is the freeway inside the computer that is used to connect the processor and memory with other devices. Some busses are as small as 16 bits, others are as large as 128 bits.

Digital Camera & Scanner - Both devices use a charge-coupled device (CCD), which is a row of photodiodes, to capture the image. Photodiodes are small devices made of a light absorbing material that turns light into electrical energy. Once the light is captured and changed to electrical energy, the analog-to-digital (ADC) chips will convert the current of energy into 1 and 0 for the processor to manipulate. When the processor finishes its jobs, the digital data is sent to the digital-to-analog (DAC) chips in the video card which change the data back to analog signal developing the image on the screen.

IDE - Integrated Drive Electronics is a term developed by the American National Standards Institute (ANSI) for integrating the hard drive controller card with the motherboard.

Keyboard - One of the peripheral devices that inputs instructions to the computer. The current Windows based keyboard has 104 keys. The keyboard has a constant flow of electrical current through each key and a small processor, which constantly scans the current and send any information to the BIOS. When striking one key, the current will be interrupted and the processor will send a code to the BIOS to be translated to ASCII code, then letters and numbers appear on the screen.

Modem - It transfers data from one computer to another by sending packets of bits back and forth.

Monitor - It translates the data sent from the video adapter into viewable images instead numbers. A cathode-ray tube is used to display the images. The signals determine the color that appear at each specific spot on the monitor.

Mouse - A device that inputs instructions telling the cursor on the screen where to move. When a mouse moves, the rubber ball moves the two rollers touching it. One of the rollers causes to horizontal movement of the cursor and the other causes vertical movement. The movement is being recorded as signals. With the greater number of signals, the farther the cursor is moved from the origin. Since the rollers go in circles, the signals are being measured in frequency; the smaller the interval, the faster the cursor will move. When moving the mouse diagonally, both signals are sent to the operation system to determine the direction. All the signals of the mouse activity are sent to the operating system for calculation

Parallel port - Parallel port is generally used to connect the printers to a PC. It consists 25 lines, some of these lines have a distinguished task. Lines 2 - 9 are reserved for transferring data. Line 10 lets the PC knows that the data is received. Line 11 lets the PC knows that the device is busy processing the received data. Line 12 tells the PC when the printer is out of paper. Line 13 is for distinguishing the power of the device. Line 14 determines when a printer should move to the next line. Line 15 signals the PC if there is an error with the device. Line 16 is used to reset the device. Line 17 is meant to switch on/off for the device that have its power supply controlled by the PC. Line 18 - 25 are ground lines. With 8 lines to transfer data, parallel ports are faster than serial.

PCI - A PCI controller, which is found on most current motherboard, is needed in order for the processor to communicate with the component that uses the PCI slot. The controller will intercept the signals and determines which type of bus to send the signals to, i.e. PCI or ISA.

Printer - The PC sends signals to the printer buffer. The processor inside the printer will manipulate the data in the buffer and send the result to the print head, where the actual printing takes place.

Ports - Ports are used as a data connection for various external components.

Power supply - It converts wall outlet AC electrical power into suitable DC voltages, monitors the DC voltages, and removes the heat that results from the consumption of electrical power.

SCSI - SCSI can connect together up to 15 devices through a single port due to it's fast transfer rate.

Serial port - Serial port works similar to a parallel. The exception is that it has only one line to transfer data while the parallel port has 8. It transfers data from the computer to an external device.

Input/Output Devices - Microchips - Multimedia - Storage