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Data Structures using Java,
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Saturday, December 11, 2010|
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What Is an Object?
An object is a software bundle of related state and behavior. Software objects are often used to model the real-world objects that you find in everyday life.
What Is a Class?
A class is a blueprint or prototype from which objects are created.
What Is Inheritance?
Inheritance provides a powerful and natural mechanism for organizing and structuring your software.
Java Naming Conventions
Every programming language has its own set of rules and conventions for the kinds of names that you're allowed to use, and the Java programming language is no different. rules and conventions for naming your variables
Primitive Data Types
A primitive type is predefined by the language and is named by a reserved keyword. Primitive values do not share state with other primitive values. 8 primitive data types supported by the Java programming language
Arrays
An array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created. After creation, its length is fixed. learn more about Array
The Arithmetic Operators
The Java programming language provides operators that perform addition, subtraction, multiplication, and division. There's a good chance you'll recognize them by their counterparts in basic mathematics.Sample of Arithmetic Operators
The Unary Operators
The unary operators require only one operand; they perform various operations such as incrementing/decrementing a value by one, negating an expression, or inverting the value of a boolean. Sample of Unary Operators
The Equality and Relational Operators
The equality and relational operators determine if one operand is greater than, less than, equal to, or not equal to another operand. The majority of these operators will probably look familiar to you as well. Sample of Equality and Relational Operators
The Conditional Operators
The && and || operators perform Conditional-AND and Conditional-OR operations on two boolean expressions. These operators exhibit "short-circuiting" behavior, which means that the second operand is evaluated only if needed. Sample of Conditional Operators
Expressions, Statements, and Blocks
Operators may be used in building expressions, which compute values; expressions are the core components of statements; statements may be grouped into blocks. Learn more about Expressions, Statements, and Blocks
Control Flow Statements
The statements inside your source files are generally executed from top to bottom, in the order that they appear. Control flow statements, however, break up the flow of execution by employing decision making, looping, and branching, enabling your program to conditionally execute particular blocks of code.
This describes the decision-making statements (if-then, if-then-else, switch), the looping statements (for, while, do-while), and the branching statements (break, continue, return) supported by the Java programming language.
Java Naming Conventions
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Every programming language has its own set of rules and conventions for the kinds of names that you're allowed to use, and the Java programming language is no different. The rules and conventions for naming your variables can be summarized as follows:
- Variable names are case-sensitive. A variable's name can be any legal identifier — an unlimited-length sequence of Unicode letters and digits, beginn(Winwith a letter, the dollar sign "$", or the underscore character "_". The convention, however, is to always begin your variable names with a letter, not "$" or "_". Additionally, the dollar sign character, by convention, is never used at all. You may find some situations where auto-generated names will contain the dollar sign, but your variable names should always avoid using it. A similar convention exists for the underscore character; while it's technically legal to begin your variable's name with "_", this practice is discouraged. White space is not permitted.
Primitive Data Types
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A primitive type is predefined by the language and is named by a reserved keyword. Primitive values do not share state with other primitive values. The eight primitive data types supported by the Java programming language are:
- byte: The byte data type is an 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive). The byte data type can be useful for saving memory in large arrays, where the memory savings actually matters. They can also be used in place of int where their limits help to clarify your code; the fact that a variable's range is limited can serve as a form of documentation.
- short: The short data type is a 16-bit signed two's complement integer. It has a minimum value of -32,768 and a maximum value of 32,767 (inclusive). As with byte, the same guidelines apply: you can use a short to save memory in large arrays, in situations where the memory savings actually matters.
- int: The int data type is a 32-bit signed two's complement integer. It has a minimum value of -2,147,483,648 and a maximum value of 2,147,483,647 (inclusive). For integral values, this data type is generally the default choice unless there is a reason (like the above) to choose something else. This data type will most likely be large enough for the numbers your program will use, but if you need a wider range of values, use long instead.
Arrays in Java Programming Language
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Data Structures using Java
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An array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created. After creation, its length is fixed. You've seen an example of arrays already, in the main method of the "Hello World!" application. This section discusses arrays in greater detail.
An array of ten elements |
Each item in an array is called an element, and each element is accessed by its numerical index. As shown in the above illustration, numbering begins with 0. The 9th element, for example, would therefore be accessed at index 8.
Sample code that use Arithmetic Operators in Java
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The Java programming language provides operators that perform addition, subtraction, multiplication, and division. There's a good chance you'll recognize them by their counterparts in basic mathematics. The only symbol that might look new to you is "%", which divides one operand by another and returns the remainder as its result.
+ additive operator (also used for String concatenation)
- subtraction operator
* multiplication operator
/ division operator
% remainder operator
+ additive operator (also used for String concatenation)
- subtraction operator
* multiplication operator
/ division operator
% remainder operator
Sample Code that use Unary Operators in Java
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The unary operators require only one operand; they perform various operations such as incrementing/decrementing a value by one, negating an expression, or inverting the value of a boolean.
+ Unary plus operator; indicates positive value (numbers are positive without this, however)
- Unary minus operator; negates an expression
++ Increment operator; increments a value by 1
-- Decrement operator; decrements a value by 1
! Logical complement operator; inverts the value of a boolean
+ Unary plus operator; indicates positive value (numbers are positive without this, however)
- Unary minus operator; negates an expression
++ Increment operator; increments a value by 1
-- Decrement operator; decrements a value by 1
! Logical complement operator; inverts the value of a boolean
Sample Code that use Equality and Relational Operators in Java
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The equality and relational operators determine if one operand is greater than, less than, equal to, or not equal to another operand. The majority of these operators will probably look familiar to you as well. Keep in mind that you must use "==", not "=", when testing if two primitive values are equal.
== equal to
!= not equal to
> greater than
>= greater than or equal to
< less than <= less than or equal to
== equal to
!= not equal to
> greater than
>= greater than or equal to
< less than <= less than or equal to
Sample Code that use Conditional Operators in Java
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The && and || operators perform Conditional-AND and Conditional-OR operations on two boolean expressions. These operators exhibit "short-circuiting" behavior, which means that the second operand is evaluated only if needed.
&& Conditional-AND
|| Conditional-OR
class ConditionalDemo1 {
public static void main(String[] args){
int value1 = 1;
int value2 = 2;
if((value1 == 1) && (value2 == 2)) System.out.println("value1 is 1 AND value2 is 2");
if((value1 == 1) || (value2 == 1)) System.out.println("value1 is 1 OR value2 is 1");
&& Conditional-AND
|| Conditional-OR
class ConditionalDemo1 {
public static void main(String[] args){
int value1 = 1;
int value2 = 2;
if((value1 == 1) && (value2 == 2)) System.out.println("value1 is 1 AND value2 is 2");
if((value1 == 1) || (value2 == 1)) System.out.println("value1 is 1 OR value2 is 1");
Different Operators Use in Java
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Different Operators Use in Java
The following quick reference summarizes the operators supported by the Java programming language.
Simple Assignment Operator
= Simple assignment operator
Arithmetic Operators
+ Additive operator (also used for String concatenation)
- Subtraction operator
* Multiplication operator
/ Division operator
% Remainder operator
The following quick reference summarizes the operators supported by the Java programming language.
Simple Assignment Operator
= Simple assignment operator
Arithmetic Operators
+ Additive operator (also used for String concatenation)
- Subtraction operator
* Multiplication operator
/ Division operator
% Remainder operator
Expressions, Statements, and Blocks in Java
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Now it's time to learn about expressions, statements, and blocks in Java. Operators may be used in building expressions, which compute values; expressions are the core components of statements; statements may be grouped into blocks.
Expressions
An expression is a construct made up of variables, operators, and method invocations, which are constructed according to the syntax of the language, that evaluates to a single value.
Sample Code of "for Statement" in Java
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for Statement
class ForDemo {
public static void main(String[] args){
for(int i=1; i<11; i++){
System.out.println("Count is: " + i);
}
}
}
The output of this program is:
Count is: 1
Count is: 2
Count is: 3
Count is: 4
Count is: 5
Count is: 6
Count is: 7
Count is: 8
Count is: 9
Count is: 10
Count is: 7
Count is: 8
Count is: 9
Count is: 10
class ForDemo {
public static void main(String[] args){
for(int i=1; i<11; i++){
System.out.println("Count is: " + i);
}
}
}
The output of this program is:
Count is: 1
Count is: 2
Count is: 3
Count is: 4
Count is: 5
Count is: 6
Count is: 7
Count is: 8
Count is: 9
Count is: 10
Count is: 7
Count is: 8
Count is: 9
Count is: 10
Sample Code of while and do-while Statements in Java
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while Statements
class WhileDemo {
public static void main(String[] args){
int count = 1;
while (count < 11) {
System.out.println("Count is: " + count);
count++;
}
}
}
do-while Statements
class DoWhileDemo {
public static void main(String[] args){
int count = 1;
do {
System.out.println("Count is: " + count);
count++;
} while (count <= 11);
}
}
class WhileDemo {
public static void main(String[] args){
int count = 1;
while (count < 11) {
System.out.println("Count is: " + count);
count++;
}
}
}
do-while Statements
class DoWhileDemo {
public static void main(String[] args){
int count = 1;
do {
System.out.println("Count is: " + count);
count++;
} while (count <= 11);
}
}
Sample Code of Switch Statement in Java
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Switch Statement
class SwitchDemo {
public static void main(String[] args) {
int month = 8;
switch (month) {
case 1: System.out.println("January"); break;
case 2: System.out.println("February"); break;
case 3: System.out.println("March"); break;
case 4: System.out.println("April"); break;
case 5: System.out.println("May"); break;
case 6: System.out.println("June"); break;
case 7: System.out.println("July"); break;
case 8: System.out.println("August"); break;
case 9: System.out.println("September"); break;
case 10: System.out.println("October"); break;
case 11: System.out.println("November"); break;
case 12: System.out.println("December"); break;
default: System.out.println("Invalid month.");break;
}
}
}
class SwitchDemo {
public static void main(String[] args) {
int month = 8;
switch (month) {
case 1: System.out.println("January"); break;
case 2: System.out.println("February"); break;
case 3: System.out.println("March"); break;
case 4: System.out.println("April"); break;
case 5: System.out.println("May"); break;
case 6: System.out.println("June"); break;
case 7: System.out.println("July"); break;
case 8: System.out.println("August"); break;
case 9: System.out.println("September"); break;
case 10: System.out.println("October"); break;
case 11: System.out.println("November"); break;
case 12: System.out.println("December"); break;
default: System.out.println("Invalid month.");break;
}
}
}
Sample Code of if-then and if-then-else Statements in Java
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The if-then Statement
void applyBrakes(){
if (isMoving){ // the "if" clause: bicycle must moving
currentSpeed--; // the "then" clause: decrease current speed
}
}
void applyBrakes(){
if (isMoving) currentSpeed--; // same as above, but without braces
}
void applyBrakes(){
if (isMoving){ // the "if" clause: bicycle must moving
currentSpeed--; // the "then" clause: decrease current speed
}
}
void applyBrakes(){
if (isMoving) currentSpeed--; // same as above, but without braces
}
How to program in JAVA?
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How to program in JAVA?
1. Open Notepad.
2. Type your Java program
3. Save your java program in C:\jdk1.4\bin using the format for the filename filename.java
4. Open MS-DOS, click Start > click RUN > type COMMAND then press ENTER Key.
5. Change the prompt to C:\jdk1.4\bin by typing cd\jdk1.4\bin PRESS ENTER
6. Compile the your saved java program by using the JAVAC.exe program. Type javac filename.java.
7. Run your program by using the java command: java filename
Entity Relationship Modelling (ER Model)
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Database Management Systems
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In an effective system, data is divided into discrete categories or entities. An Entity Relationship (ER) Model is an illustration of various entities in a business and the relationships between them. An ER model is derived from business specifications or narratives and built during the analysis phase of the system development life cycle.
ER models separate the information required by a business from the activities performed within a business. Although businesses can change their activities, the type of information tends to remain constant. Therefore, the data structures also tend to be constant.
Database Management Systems (DBMS) Terminologies
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Database Management Systems
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Data- Every organization has some information needs. A library keeps a list of members, books, due dates, and fines. A company needs to save information about employees, departments, and salaries. These pieces of information are called data.
Database- An organized collection of information.
Database Management Systems- A program that stores, retrieves, and modifies data in the database on request. There are four main types of databases: hierarchical, network, relational, and more recently object relational.
Microsoft Access Database- A collection of data and objects, such as tables, queries, or forms, related to a particular topic or purpose.
Basic Computer Hardware
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hardware
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The personal computer (PC) is one complex piece of machinery. Its made up of many individual components that will baffle the uninitiated. To learn about PCs, one has to have a desire to learn and experiment. This is not to say that PC technology is terribly hard to learn. All you need to know is the how a basic PC is set up, and what components are required.
After learning the basics, its a matter of self experimentation and reading - with time, you'll be one of the pros! This article aims to provide you with at least some basic knowledge of PCs so that you can move on to learn more if you wish.
How to Fix a DLL Error?
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Computer Tips and Tricks
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Friday, December 10, 2010|
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If you have received a DLL error on your computer, this is usually a symptom of other issues. Installing a new program or a virus can cause dll errors on your PC. When a DLL file is corrupted or missing other glitches and problems can quickly follow.
If you ever encounter problems for instance slower computer processing, programs opening slowly or not at all, sluggish web surfing, blue screens, other file problems, including a possible full crash on your pc, then this is a sign that you could be having DLL error issues. It is highly advised that you get a FREE scan of your files when you experience missing DLL errors. Do it the soonest possible time.
Trick To Burn Audio Files With Windows Media Player
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Computer Tips and Tricks
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Place a CD-R or CD-RW disc in the drive, open Windows Media Player and click on the Copy button to CD or device, which appears on the left bar. This causes two tables to see the program window, marked on the top and elements to copy and Elements on the device.
In the left box is a drop-down list, called Playlist to copy, where appear the songs and data of each title, duration and file size (well, there is a checkbox to the left of each song).
Usually, the list you see is the last one used, and can modify by clicking the Edit Playlist button.
To create a completely new list, open the drop-down list and click on the Create a new playlist (the table is empty), then click on the Edit Playlist button.
Ways to Change the Battery in a Computer
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Computer Tips and Tricks
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Computer has battery or a special chip which retains computer (CMOS) settings and also runs the computer lock even after the computer itself is turned off. When you have to reset the date and the time on the computer every time you start it, you will need to replace the battery of your computer. This procedure is applied to IBM-compatible computers which have a replaceable battery or the connector for the space battery. At this time, this article is going to deliver several tips to change the battery in a computer.
How to get rid of the Trojan Virus in your Computer
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Computer Tips and Tricks
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When it comes to computer security the Trojan horse is a formidable virus that attaches itself to normal files, breaches security and enters the computer whenever the user downloads anything from the internet. Its presence is completely hidden from the user, as it functions invisibly to infect the files one by one. Moreover, it can also read personal information such as the credit card number and allow other malicious users to view them. Because such a dangerous virus exists, it is imperative for you to know the means to get rid of it.
When it comes to the Trojan virus, and you are thinking about security a little prevention is always better than a mass cure. If you are a cautious user and extremely careful about what you download, getting your files from friends and trusted sources, you will never need to know how to get rid of the Trojan virus. You don't want to have to worry about how to get rid of Trojan Horse virus, because that means you're already in a fair amount of trouble.
Electronic Data Interchange (EDI)
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Management Information System
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Electronic Data Interchange (EDI) is the structured transmission of data between organizations by electronic means. It is used to transfer electronic documents or business data from one computer system to another computer system.
Electronic Data Interchange (EDI) Consists of direct computer-to-computer transmissions among multiple firms of data in a machine-readable, structured format
Electronic Commerce
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Management Information System
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Electronic commerce, commonly known as e-commerce or eCommerce, consists of the buying and selling of products or services over electronic systems such as the Internet and other computer networks. The amount of trade conducted electronically has grown extraordinarily with widespread Internet usage.
The use of commerce is conducted in this way, spurring and drawing on innovations in electronic funds transfer, supply chain management, Internet marketing, online transaction processing, electronic data interchange (EDI), inventory management systems, and automated data collection systems. Modern electronic commerce typically uses the World Wide Web at least at some point in the transaction's lifecycle, although it can encompass a wider range of technologies such as e-mail as well.
Information Services | Computer-Based Information System
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Management Information System
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Saturday, December 4, 2010|
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Information specialists have full-time responsibility for developing and maintaining computer-based systems
End-User Computing (EUC)
End-user computing
Traditional Communication Chain
End-User Computing (EUC)
End-user computing
- Development of all or part of applications
- Information specialists act as consultants
- Increased computer literacy
- IS backlog
- Low-cost hardware (the PC)
- Prewritten software (electronic spreadsheets)
The End-User Computing Communication Chain
System Components | Computer-Based Information System
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Management Information System
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Component parts of a system that can control its own operations
Open versus Closed Systems
- Open system: Connected to its environment by means of resource flows
- Closed system: Not connected to its environment
1. Physical system
- The business firm
- Composed of physical resources
- Represents a physical system
- Uses conceptual resources
- Information
- Data
Business operations are embedded within a larger environmental setting
- Reduces complexity
- Requires good objectives
- Emphasizes working together
- Acknowledges interconnections
- Values feedback
Main Resources in Computer-Based Information System
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Management Information System
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Main Resources in Computer-Based Information System
1. Physical:
- Personnel
- Material
- Machines (including facilities and energy)
2. Conceptual:
- Money
- Information (and data)
How Resources are Managed
- Acquire
- Assemble, or prepare
- Maximize use
- Replace
Factors Stimulating Interest in Information Management
1. Increasing complexity of business activity
- International economy
- Worldwide competition
- Increasing complexity of technology
- Shrinking time frames
- Social constraints
2. Improved computer capabilities
- Size
- Speed
Who are the users of the System?
- Managers
- Nonmanagers
- Persons & organizations in the firm’s environment
Steps to Fix The 1706 Error in Windows
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Computer Tips and Tricks
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Thursday, December 2, 2010|
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The 1706 error is a common problem for millions of Windows PCs, and is caused by your PC being unable to correctly install a piece of software onto your computer. The error is generally caused by your computer's inability to correctly read the installation files required to put the software onto your PC, or from having some other problems with the settings of your system.
Causes of 1706 Error:
- You originally installed Microsoft Office from a network administrative installation.
- The network administrative installation is no longer available to you.
- You are trying to use an Office CD-ROM when you are prompted by the Windows Installer for an Office source location.
- You click Cancel when you are prompted to Insert the CD
- You have registry errors on your PC
How to Find Deleted Files on Your Computer?
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Computer Tips and Tricks
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The last thing that you would want to happen is to lose a file or data on your computer because of hard drive failure. You have to know that no matter what you do, you cannot stop the drive from failing and it can happen to anyone. Once it happen to you, you need to immediately locate cheap data recovery software that can help you get your files back. How to find deleted files is one of the most daunting job that you can face in your life, but there is nothing that you can do but to recover these files.
This kind of problem usually happens to students and employees. It always affects important files that you need for school or work. Sometimes you might think that your computer sabotages your future, but your computer does not know when it will exactly happen.
How to Recover Lost Data?
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Computer Tips and Tricks
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All computer users should have access to data recovery information. Almost everyone uses some type of computer daily, whether it is a laptop, desktop of another kind of device, like a mobile phone, iPhone, iPad or MP3 player. We use computers to manipulate data, but computers are machines and machines break down.
Computers sometimes lose data. Lost data can often be recovered from damaged, corrupted or failed storage media like hard drives (internal or external), CDs, DVDs, RAIDs (a set of hard disks that are used in a cluster or array to store and manage data) or memory sticks. Data is lost through one of two ways. A storage device may be physically damaged, making stored data inaccessible. Physical damage to a disk may result from one of many causes.
How to Speed Up your Computer
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Computer Tips and Tricks
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Are you tired using a slow computer?. Before you try throwing your personal computer into the trash can, try the following to speed up Windows:
Get a Registry Cleaner- There is a lot of software to speed up Windows. Registry Cleaners, for instance takes care of the registry files that your computer frequently generates and preserves. Because of Registry Cleaners you have the alternative of saving only the registry files that are often in use by your PC. While these files are relatively small, they in general eat up bigger space after a while. IMPORTANT: Always make sure you back up your registry files before making any changes.
Steps to Find Free Space and Transfer Speed of Your Hard Drive
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hardware
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Steps to Find Free Space Are Available in Your Hard Drive
- Step 1: Move your mouse to the bottom left-hand corner of the screen and left-click on the round Windows button. This will bring up a menu with two panels.
- Step 2: On the right side of the Menu, click on the option "Computer." This will bring up a file browser that shows all the hard drives and other devices connected to your computer.
- Step 3: Left-click once on any drive and you will see a display showing the total capacity and the amount of free space available.
- Step 4: For further information, right-click on the drive name and select "Properties." The properties window will open. Click on the "General" tab, which will show a graphical representation of the total space and free space available.
Open Source Printer Software
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sofware
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There was a crowd of people that once thought, and still do, that computer software should be a free service. They created something very inspired- put simply, open source software was designed so that others could continue to improve upon the original design of a program, thereby republishing and offering an improved product for the customer.
This software is often available for free, but occasionally has a cost much lower than alternative programs. Plus, it offers flexibility and more frequent updates and technology gurus continue to improve upon the existing model. In fact, you, yourself, could make changes to this type of software to make it do exactly as you please. That is if you are an expert in the field.
There are many uses for open source software. Currently programs can be found for word processing, to measure business productivity, manage clientele, email, instant message, and browse the web. Each has the ability to be adjusted to fit personal needs and wants. And, those are just a few from a long list.
Advantages of using Joomla 1.5 template
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Web Design
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Website nowadays are far beyond the traditional website in early years. One of a key to success to your business websites is the presentation with Joomla 1.5 templates you can achieved a high levels of presentation. Presentable website can attract more client to your site. The advantage of Joomla 1.5 templates is their unique designs and pristine graphics that capture the attention of your online client. Finally Joomla 1.5 templates provide a company with a website that presents an ease of access.
Here are some advantages of using Joomla 1.5 templates:
- Easy Navigation - Joomla 1.5 templates is design in generating a web page that are simple to navigate beacause of its organized layouts. A web page that is easy to navigate can attract more visitors to enter your site.
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