Complete Computer Knowledge Portal

Wednesday, June 19, 2013

Selection Sort

It is the sorting technique with O (n2) Complexity. Hence this technique can’t be used for sorting large lists. This sorting technique finds maximum Value from the list and swaps it with first element. This process is repeated for the remaining list until list is not sorted.

Only n swaps are required to swap n number of elements.

Example: Consider the following unordered list   


Bubble Sort

It is the simplest type of sorting technique. In this sorting technique, first two elements are compared and if first element is greater than second, they are swapped. This process is repeated for each pair of adjacent elements to the end of the data set. It again starts with first two elements and repeat the process until no swap occurs.
This sorting technique can only be used for sorting small lists. This technique can also be used for the large lists if only few elements require sorting.

Important: Average and worst case performance of this sorting technique is O (n2).

Addressing Modes

Addressing modes are the way to identify operands in machine language instructions. It defines how to calculate effective address of operand with the information held in registers and/or constants contained by a machine instruction.
Some commonly used addressing modes are as follows:

Implied Mode: In this addressing mode operands are specified implicitly in the definition of instruction. E.g. complement Accumulator. In this instruction operand in the accumulator is implicitly defined in the instruction.
Example: CLA

Tuesday, June 18, 2013

Distributed Data Processing (DDP)

It is a configuration in which many geographically dispensed or distributed independent computers are connected by means of computer networks. In this type of configuration Programs, data and other resources are shared among several users who are geographically far away from one another. This provides the facility of better resource use to the end users.

This approach is different from centralized system because computers are installed at different locations and each of them performs independent data processing. Each computer in DDS is designed for a specific task.

Scanning Technologies

Four types of scanning techniques are used by manufactures to generate soft copy of color images or documents:
1) Multi Pass Technology
2) Single Pass Technology
3) Photo Multiplier Tubes(PMT) Technology
4) Contact I Image sensing Technology.

Enhanced Graphics Adapter (EGA)

It is the Computer Display standard that was introduced by IBM in September 1984.This display standard is between CGA and VGA in terms of color and space resolution. Some main Features of this video standard are as follows:

a) EGA can generate display of 16 simultaneous colors from a palette of 64 at a resolution of up to 640×350 pixels.

b) EGA card has a max. Of 128K video memory and fits into RAM just above 640K limit.

Video Graphics Array(VGA)

This video system was introduced by IBM in 1987.VGA was implemented with VLSI (Very Large Scale Integration) on a single card with 8 bit interface support. VGA is referred to as Array instead of Adapter because it replaced Motorola 6845 and other discrete logic chips that were used in previous video standards. Main Features of this Video Standard are as follows:

a) Analog display output allows display of 16 colors from a palette of 2, 62,144 colors at 640 X 480 resolutions.

b) It was cheap and was backward compatible with MDA, CGA and EGA Cards.

Flash Memory

It is a type of EEPROM that is much faster than traditional EEPROM. It reads or writes data in form of blocks. Block size is usually 512 bytes.

Sometimes flash memory is termed as flash RAM. But there is a much difference between flash RAM and flash memory. Flash RAM requires constant power to maintain its contents whereas flash ROM can store its contents even without any power.


It is the art or science to design ciphers, i.e. a message written in secret code. It is the key enabling technology that is used to protect distributed systems. The Process of breaking these secret codes is called cryptanalysis. Input text that is provided for encryption is called plaintext and the encrypted text so obtained as output is called cipher text.

There are three main techniques that are used to generate strong cipher:

Monday, June 17, 2013

Ext, Ext2, Ext3 and Ext4 Linux File Systems

EXT (Extended File System)

 It was the first file system for Linux kernel developed by Remy Card in April 1992. It was based on metadata structure .It was the first file system that implemented VFS( Virtual File System ). Some features of this file system are as follows:
a) It supports maximum partition size up to 2 Giga Bytes.
b) It support file name size up to 255 characters long.
c) It lacked in timestamps (the current time of an event that is recorded by a computer) for modifications to inodes (a data Structure that stores all the information about a file except its name and its actual data) and to data.
d) It lacked in providing support for separate access for each user and group.
e) Linked list technique was used for file handling.

Sunday, June 16, 2013

Display Problem Solutions

Computer is nothing if it is not generating display because user can’t work on that. This Problem can arise due to any of the following reason:
a) Due to Monitor Problem
b) Due to Motherboard/RAM Problem
c) Due to loose Connections
d) Due to wrong CMOS settings
e) Due to Wrong Display Settings
f) SMPS faulty

Here are some troubleshooting steps that can be used to resolve display problems.

Case1: If Monitor is Faulty
Symptoms: Faded Colors, Red Display, Green Display, Blue Display, distorted display, lines on monitor, display too bright or too fade.
Solution: This problem can be due to any of the following reasons
1) Display connection is loose, Tight them Properly
2) Data Cable is Faulty, Change that.
3) PCB is dry soldiered, Re Soldier the PCB, especially neck card.
4) Neck card IC can be faulty, Change that.
5) FBT Faulty, Change that with same value