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A+ Essentials  Technologies

10. computers

PDA: Handheld PCs are also referred to as Personal Digital Assistants (PDAs).


- Nickel Cadmium battery is not environmentally friendly and not as efficient as Nickel / Metalhydride or Lithium Ion. Nickel / Metal hydride, though environmentally friendly, not as efficient as Lithium Ion. Lithium Ion battery is environmentally friendly and very efficient.

- Passive matrix displays are most commonly used and cheaper than Active matrix displays. Also, passive matrix displays consume less power. However, the advantages of active matrix display are that they can handle faster screen image transition, and display is clearly viewable, even from slant angles.

- Laptops most widely use PCMCIA cards, also referred to as PC cards.
Normally, desktop processors consume higher power compared to laptop processors. Laptop processors are optimized for lesser power consumption, so that the heat produced is also less. This is to take care of poor ventilation conditions in a laptop computer.

General PC error codes and probable causes:

100-199 : System board failures
200-299 : Memory failures
300-399 : Key board failures
400-499 : Monochrome video problems
500-599 : Color video problems
600-699 : Floppy disk errors
1700-1799: Hard disk problems.

Some of the frequently encountered error codes and their corresponding error messages are given below:

Error Code

Error Message


CMOS battery failure: Replace the CMOS battery


Memory size error : If the error occurs after memory upgrade, run SETUP program.


Memory test failed : RAM chips failed, one or more may need to be replace.


Keyboard error: You may have to check the key board

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