Showing posts with label Computer Science(Conceptual). Show all posts
Difference Between Virus,Worms,Trojan and Spyware
Ok lets start from the introduction of viruses
Virus:-A virus is a self replicating program that attaches itself to an executable file.When the file is executed the virus automatically gets executed and enters into system memory .Once it enters into system memory it either searches for other files that can be infected or stays in the background and infect the files that are uses the virus infected program.
Worms:Worms are very similar to viruses but differ in way that they donot bind themselves to executable files instead to replicate themselves they uses the network.If you find excessive use of your network bandwidth then you may be infected by a worm.So,a worm donot require a user to execute any file for its execution it can work without user intervention.
Trojan Horse:-A trojan horse is harmful program which may seem harmless to the user before its installation but instead it is programmed or reverse engineered to facilitate unauthorised remote access to the computer.Trojan’s donot replicate themselves.
Spyware:-A spyware is a program that secretly monitor and collects pieces of information.They usually run in stealth mode and cannot be detected easily.Keyloggers is a great example of spyware software.These are not limited to just spying but can also send data to remote computers .
Indicates a video error has occurred and the BIOS cannot initialize the video screen to display any additional information
POST troubleshooting steps.
Additional information
This document is intended to help users who are experiencing issues with the POST and may have any of the below symptoms.
- Computer beeps irregularly when the computer is turned on.
- Computer turns on but does not boot or do anything.
- Computer reboots every few seconds.
Answer
Tip: Make sure the computer turns on, if nothing happens (no lights, no sound, no fans, etc.) the computer has a power related issue.
Caution: Some of the below steps recommend removing physical parts within the computer. While in the computer it is highly recommend that you be aware of ElectroStatic Discharge (ESD)and its potential hazards.
Remove new hardware
If any new hardware has been recently added to the computer, remove that hardware to make sure it is not the cause of your issue. If after removing the new hardware your computer works it's likely the computer is either not compatible with the new hardware or a system setting needs to be changed to work with the new hardware device.
Remove any disks or USB devices
Remove any disks, CD's, DVD's that are in the computer and if any USB devices (iPods, drives, phones, etc) are connected disconnect all of them as well. Reboot the computer and see if anything changes.
Disconnect external devices
Remove everything from the back of the computer except the power cable. Turn on the computer and see if it beeps normally. If the computer has never beeped keep the monitor or display connected to see if any change occurs.
Identify beep code
If you are receiving a sequence of beeps see the beep code page for a listing of different beep codes and their explanation or your motherboard or computer documentation. These beep codes are meant to help identify what computer component is failing or bad. If your beep code is not listed, continue troubleshooting.
Check all fans
Make sure all fans are running in the computer. If a fan has failed (especially the heat sink fan for the CPU) your computer could be overheating or detecting the fan failure causing the computer not to boot.
Check all cables
Verify that all the cables are properly connected at that there are no loose cables by firmly pressing in each cable.
- All disk drives should have a data cable and power cable connected to them.
- Your power supply should have at least one cable going to the motherboard. Many motherboards may also have additional cables connected to them to supply power to the fans.
Disconnect all expansion cards
If the above recommendations still have not resolved the irregular POST, disconnect the riser board (if applicable) and each of the expansion cards. If this resolves the issue or allows the computer to POST connect one card at a time until you determine what card is causing the issue.
Disconnect all drives
If you were unable to determine by the beep code what is failing or do not have a beep code disconnect the IDE, SATA, SCSI, or other data cables from the CD-ROM, hard drive, and floppydrive from the Motherboard.
If this resolves your irregular POST or generates error messages re-connect each device until you determine what device or cable is causing the issue. In some situations it can also be a loose cable connection that causes the issue.
Remove the RAM
If you continue to to receive the same problem with all the above hardware removed, disconnect the RAM from the Motherboard and turn on the computer. If the computer has a different beep code or if your computer was not beeping and is now beeping turn off your computer and try the below suggestions. Making sure to turn off the computer each time you're adding and removing the memory and then turning the computer back on to see if the suggestion resolves the issue.
- Re-insert the memory into the same slot.
- If you have more than one stick of memory remove all but one stick of memory, try rotating through each stick.
- Try one stick of memory in each slot.
If you're able to get the computer to boot with one or more of the sticks of memory it's likely you're dealing with some bad memory. Try to identify what stick of memory is bad and replace it.
If you're able to get memory to work in one slot but not another slot. You're motherboard is defective you can either workaround the issue by running the memory in a different slot or replace the motherboard.
Power cycle the computer
In some situations a computer may have power related issues often caused by either the power supply or the motherboard. To help determine if this is the cause of your issue try turning the computer on, off, and back on as fast as possible, making sure the computer power light goes on and off each time. In some situations you may be able to temporarily get the computer to boot.
This should only be used as a temporary workaround if you're able to get this to work. Often this is good for users who may have not done a backup and need to get the computer up one more time to copy files before starting to replace hardware.
Disconnect and reconnect the CPU
For users who are more comfortable working with the inside of their computer or who have built their computer one last recommendation before assuming hardware is bad is to reseat the CPUby removing it and putting it back into the computer.
Bad motherboard, CPU, RAM, or power supply
If after doing all of the above recommendations you continue to have the same issue unfortunately it is likely that you have bad Motherboard, PSU, CPU, or RAM. The next step would be either to replace these components or have the computer serviced. If you plan on doing the repairs yourself or you are a repair shop it is suggested that you replace the Motherboard first, RAM, CPU, and then power supply in that order or try swappable parts from other computers.
CMOS shutdown Read/Write error
How to replace the CMOS battery
Issue
How to replace the CMOS battery.
Cause
Like any battery the computer CMOS battery can fail or lose its charge.
Solution
If your computer is losing its time or date settings, or you are receiving a message CMOS Read Error, CMOS checksum error, or CMOS Battery Failure, first try leaving the computer on for 24-hours. In some cases this can charge the battery and resolve your issue. This often resolves CMOS battery related issues when a computer has been left off for several months. If this does not resolve your issue follow the below steps.
Locate your CMOS battery
Caution: When inside your computer make sure you're aware of ESD and all it's potential dangers.
Open the computer case and find the battery on the computermotherboard, verify that it will be accessible and that it can be removed. Most computers today use a coin cell CMOS battery as shown in the image to the right.
If you are unable to locate your CMOS battery refer to your motherboard or computer documentation or contact your computer manufacturer for additional assistance in locating it.
Obtain battery information
Unfortunately, most manufacturers will not list the exact type and model of your CMOS battery; therefore, once you have located the battery, write down all information about the battery (Voltage, chemistry, wiring, and packaging). If possible, remove the battery and take it to the location you plan on purchasing a new battery from. The part number for this battery for most computers is CR2032.
Additional buying information can be found on our battery buying tips page.
Removing the battery
Caution: When inside your computer make sure you're aware of ESD and all it's potential dangers.
If you're computer is using a coin cell battery similar to the above example picture. Removing the battery is relatively simple. use your fingers to grab on the edge of the battery and pull it up and out of the container holding it. Some motherboards have a clip holding the battery down. If your computer has this clip you may need to use one had to move the clip up and the other hand to pull the battery out.
Unfortunately, not all CMOS batteries are removable; some manufactures will only allow a replacement battery to be added. If you're not using a coin cell battery and are not able to determine how to remove it refer to your motherboard or computer documentation or contact yourcomputer manufacturer for additional assistance in removing the battery or how to insert a new replacement battery.
Users with computers that do not have removable batteries only options to install a new battery will most likely also need to set a jumper when adding the new battery into their computer.
Insert the new battery
Once you have purchased a new battery, remove the old battery (as instructed above) and replace it with the new battery.
Enter CMOS values
Once the battery is replaced turn on the computer and resetting the CMOS values to the defaults. After the values have all been entered make sure to save the settings before exiting. Many CMOS setups allow you to press a key (such as F10) to save values and exit all in one action.
If after following all the above steps you continue to experience the same error when your computer starts or your computer is still unable to keep the stored values it's likely that you're experiencing a more serious issues. Most likely causes are bad power supply or bad motherboard.