STUDY OF FRONT PANEL AND BACK PANEL OF ATX CABINET

Front Panel

In the following picture, We can see front of a basic computer. We are starting at the bottom and going up, we can see that there is a large round button. That's the power switch. Its used to turn the computer on and off. 

Above the power button, we can see a row of ports. The four rectangular ports are USB ports. They are typically used with USB flash drives or external hard drives to transfer information from the computer. Between the USB ports are the headphone and microphone jacks. These can be used for gaming headsets. The smaller button to the right of the right-most USB port is the reset button. The reset button should only to be used in the case of a serious crash where the computer freezes. On some machines.

In the front of computer there is only one drive. It's an optical drive (term used for CD, DVD and Blu-ray drives - drives that read and write with a laser). We need to burn optical disks.

Most computers have both 'power lights' and 'hard drive lights'. The power light (power LED) lets you know when the computer is on. If it's on constantly, the computer is operating normally. If it's blinking, it's likely that the computer has gone into either hibernation or suspend mode. 

The hard drive LED lights up when the hard drive is being accessed or is otherwise active. On the computer below, the lights for power and the hard drive are readily visible.

Back Panel

At the top of this computer, you can see where the power source plugs in. It is plugged into the 'power supply'. The power supply converts the mains voltage 230 VAC to the various voltages needed by the computer. On this particular power supply, you can see 2 switches. One is the main power switch. The other is the voltage selector switch. The main power switch completely cuts power to the power supply. Switching this off is essentially the same as unplugging the power supply. When the end of the switch with the '1' is depressed, the power supply is able to power up when asked to by the motherboard. The voltage selector switch allows the power supply to operate with different mains voltages. 

Back Panel Connectors

P/S2 Ports:
The two P/S2 connectors are for the mouse and keyboard. Not all new computers have these. Many of the new keyboards and mice have USB plugs. If your mouse and keyboard don't have P/S2 connectors and you want to use adapters. 

USB 2.0 and Powered eSATA:
The top two ports are standard USB ports. There are two more lower on the panel and there are 3 more USB headers inside the computer. They can support 6 more USB ports. The powered eSATA can be used as USB ports also but they're designed for an external SATA drive. The eSATA connection is much faster than USB 2.0 so it's favored for transferring large files. USB 2.0 is specified because there is not a USB 3.0 that's faster than USB 2.0. This motherboard doesn't support USB 3.0.


Ethernet:
The two connectors on the left are the two USB connectors that were mentioned previously. The connector on the right is the ethernet port. This is where you make the connection to your network or to the internet. The top LED indicates when there is a connection. If it's constantly off, there is no connection/link to the network. The bottom LED on the connector indicates the speed of the connection (LED off = 10Mb/s, LED orange = 100Mb/s, LED green = 1Gb/s).

Analog Audio:
These connectors are for the analog audio inputs and outputs. Each jack is capable of carrying two independent channels. The green (front), black (rear), gray (side) and half of the orange (center channel) produce full range audio. The subwoofer only produces low frequencies. The pink (microphone) supports stereo input as does the blue

Video:

The next image shows the three video output connectors on the video graphics card. The one on the left is the DVI connector. This connector is designed to send a digital signal to a monitor but also has connections for analog video (same as the blue VGA connector). The middle connector is a standard HDMI port. This port and the DVI port (for video cards capable of doing so) can pass digital audio with the digital video signal. The cards take the S/PDIF signal from the motherboard, either via the PCI-E connector or via a 2-conductor cable.

Reference: http://www.bcot1.com/thecomputer.html