Tag Archives: integer

Java, Video

Data types in Java

A data type classifies various types of data eg. String, integer, float, boolean, the types of accepted values for that data type, operations that can be performed on the data type, the meaning of the data, and the way that data of that type can be stored.

The table below shows the most commonly used data types used in the Java programming language.

Type Description Example
int The integer (int) data type stores positive or negative whole number values. 20
float The float data type stores floating point numbers (numbers with decimal places) eg. 43.65 . Often, you will need to end a float value with an ‘f’ character eg. 43.65f 43.65f
char The char data type stores a single character such as a letter, number, space or special character (eg. a, 1, !).  A char value is always surrounded by single quotes eg. ‘a’. ‘a’
String The String data type stores letters, numbers and other characters in the form of words or sentences. A string value is always surrounded by double quotes eg. “Hello World”. “Hello world”
boolean The boolean data type stores true or false values only eg. true true

The table below shows some of the other data types used in the Java programming language.

Type Description Example
byte The byte data type stores integer numbers ranging from -128 to +127 118
short The short data type is used for integer numbers ranging from -32,768 to +32,767 -28,471
long The long data type is used for integer values exceeding 2.14 billion ‘a’
double The double data type is used for extremely long floating point numbers 1.7976931348623157 × 10^308

Sample code

The sample Java code below shows how some of the different data types can be stored in variables. Later on, we will look at how to actually work with the values of different data types (eg. math calculations with integers and floats, and decision making with booleans).

The code includes comments explaining each data type.

package myjavaproject;

public class DataTypes {
    public static void main (String[] args){
        String message = "Hello"; // variable of String data type
        char letter = 'a'; // variable of char data type
        int number = 20; // variabe of int (integer) data type
        float decimal = 43.65f; // variable of float (floating point) data type
        boolean result = true; // variable of Boolean data type
        
        // now let's output the values of the different variables
        System.out.println("Message is " + message);
        System.out.println("Letter is " + letter);
        System.out.println("Age is " + number);
        System.out.println("Score is " + decimal);
        System.out.println("The answer is " + result);
    }
}
Video, Xamarin & C#

Integers and floats in C#

In the previous tutorial we looked at how to create variables and work with the string data type in C#. In this tutorial we will look at how to work with the integer and float data types in C# and also how to convert strings to integers or floats using the int.Parse() and float.Parse() methods. You will also learn how to manipulate numbers using arithmetic operators.

Watch the video below or scroll down to see the sample code.

Sample C# code

using System;

namespace MyCSharpApp
{
  class MainClass

  {
    public static void Main (string[] args)
    {
      Console.WriteLine ("Enter two numbers...");
      float num1 = float.Parse(Console.ReadLine ());
      float num2 = float.Parse(Console.ReadLine ());
      Console.WriteLine (num1 + num2);
    }
  }
}

Arithmetic operators

Arithmetic operators are used for performing standard math operations on variables and are usually only used number variables (although they can be used for other things too).

Operator Name / description
+ Addition – this operator is used to add two numbers together. It can also be used to concatenate (join) two strings together.
– Subtraction – this operator is used to subtract one number from another.
* Multiplication – this operator is used to multiply two numbers together.
/ Division – this operator is used to divide one number by another.
% Modulus – this operator is used to divide one number by another but instead of returning the result, it returns the remainder of the division. Eg. 5%2 would return a result of 1.

Brackets can also be used for more complex math operations eg. 5 + (10 * (6 / 3) / 2);

The assignment operators follow standard mathematic order of operations. That means that the math works from left to right. Parenthesis are done first, multiplication and division comes second, and then addition and subtraction come third.

Assignment operators

Assignment operators are used to assign a value to a variable. The most frequently used assignment operator is the equals (=) sign. There are other operators as well that are used to combine multiple operations into one. The syntax of a standard variable assignment looks like this:

<variable name> <assignment operator> <value>;

For example: x = 5;

The table below shows the different assignment operators available in C#.

Operator Description
= The equals sign is used to assign the value on the right side of the equals sign to the variable on the left side of the equals sign.
+= , -= , *= and /= These assignment operators are also used to perform arithmetic operations and assign the result to the variable eg. x *= 5 is the same as saying x = x * 5.
++ and — These assignment operators are called increment and decrement operators and are used to increase or decrease the value of a variable by 5. For example, x++ is the same as saying x = x + 1.

Next tutorial: Conditional programming in C#

PHP and MySQL, Video

Data types in PHP

This tutorial explains the range of data types that can be used in PHP including:

  • String (letters, numbers and other characters – stored inside quotation marks)
  • Integer (whole positive or negative numbers)
  • Float (positive or negative real numbers – numbers with decimal place)
  • Boolean (can be only one of two possible values – either true or false)
  • NULL (no value / nothing)

String values are always stored inside quotation marks (can be double or single quotation marks, but they must match) eg. $mySentence = “Hello world”;

Integer, float and boolean values are not contained inside quotation marks eg. myNumber = 5;

It is important to note that when working with numbers, if you intend to treat a value as a number (and it will be used for numeric comparisons and calculations) such as a score in a game, then it should be in the form of an integer or float and not stored inside quotation marks. However, if a number value is not going to be used for calculations eg. a phone number or ZIP code, then it can be stored as a string value inside quotation marks.

Watch the video below and scroll down to see the sample code.

PHP sample code:

<?php
 $name = "Batman"; // strings (letters, numbers and other characters)
 $age = 25; // integers (whole positive or negative numbers - no decimal places)
 $num = 30.256; // floats (positive or negative real numbers - can have decimal place)
 $myboolean = true; // Boolean (only one of two possible values - true or false)
 $myvariable = NULL; // NULL (no value / nothing)
?>

PHP Manual references:

JavaScript, Video

Treating text input from a form as an integer or float

If you have completed the User Input with Forms tutorial, you will now know how to ask the user for text input through a form, and use that input in some way. However, if you trying collecting input from the user in the form of numbers and then try to do some logical operations on those numbers, you may run into problems.

The first problem is that any text input will be treated as a string, not an integer. So if you try to compare two numbers eg. check if the inputted number is equal to 5, JavaScript will be trying to check if a string input is equal to a number and will not be checking if an integer input is equal to a specific integer.

The video and sample code below shows an example of using parseInt() to treat text input from a textbox as an integer value. You can also use parseFloat() to parse a string as a float (real number with decimal places). The video also shows how to grab the value from a textbox by using document.getElementById(‘idname’).value so that a logical operation can happen

The example used in the video and the code below is a simple math question game. The program displays a math problem to the user. The user can enter their answer in a textbox and the page will display a message if the user gets the correct answer. Watch the video below to see how to write the code for this program.

Once you have completed the tutorial, your program should work like this:

MathGame

Here is the code for the program:

<html>
<head>
<title>Simple math game</title>
<script type="text/javascript">
var answer = 15; // this is the answer to the math question
var attempt; // the user's attempt will be stored in this variable
 
function guess(){
 attempt = document.getElementById('attempt').value;
 attempt = parseInt(attempt); // this will now treat the textbox input value as an integer
 var result = document.getElementById('result');
 
 if (attempt == answer){
 result.innerHTML = "Correct!";
 }
 else{
 result.innerHTML = "Try again.";
 }
 
}
 
</script>
</head>
<body>
 <p>What is the answer to 10+5?</p>
 <form>
 Enter your answer:<input type="text" id="attempt"/><br/>
 <input type="button" value="Submit" onclick="guess();"/>
 </form>
 <p id="result">Enter your answer in the textbox above. It must be a number only.</p>
 
 
</form>
</body>
</html>

 Next tutorial: Submitting forms

JavaScript

Data Types

This source code shows how create and use variables of different data types. Strings are text (letters, numbers and characters), integers are regular whole numbers (treated as numbers), and floats are real numbers (with decimal places eg. 4.5). You’ll also see how to use the HTML br tag to add a new line between text that is displayed in the browser.

You can watch the video about variables and data types here.

<!DOCTYPE html>
<html lang="en"
<head>
 <meta charset="utf-8"/>
 <title>JavaScript - Data Types</title>
 <script type="text/javascript">
 //integer
 var age = 20;
 document.write(age);
 
 //float
 var price = 12.95;
 document.write(price);
 
 //string
 var name = "Smith";
 var sentence = "He said \"hello\".";
 
 /*
 Just like in Python, a backslash can be used as an escape character so that
 quotation marks can be used inside a string without any errors
 You can also use single quotes to enclose a string if you want to use double quotes inside a sting
 eg. var sentence = 'He said "hello".';
 */
 
 document.write("</br>", sentence);
 //You can concatenate (join) strings using a comma and you can also use HTML tags inside quotation marks eg. </br>
 //The </br> tag is used to add a new line when the string is displayed in the browser.
 
 </script>
 
</head>
<body>
 
 
</body>
</html>
JavaScript, Video

Working with Strings in JavaScript

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This video tutorial explains how to concatenate (join) strings, convert between integers and strings, change text to uppercase and lowercase, and also introduces indexing and arrays.

You can watch the video below or click here to view it on YouTube.  This is the fourth video from the beginners JavaScript tutorial video series.

The sample code snippet below shows how to join (concatenate) strings, find the length of a string (the number of characters in a string), convert from integer to string, display specific characters in a string, split a string up and place each word in a separate array element, and convert string to uppercase and lowercase.

Don’t try all of this in one go. Have a go at one string operation at a time and only move on to the next one when you feel comfortable to.

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="utf-8"/>
 <title>JavaScript - Strings</title>
 <script type="text/javascript">
 
 var firstName = "Nicolas";
 var lastName = "Cage";
 
 // Concatenation means joining (eg. joining two strings together to form one string
 // Below, is an example of a concatenated string being held in a variable
 var joinednames = firstName + lastName;
 
 // Below, is an example of concatention with spaces added between words.
 document.write(firstName,' ',lastName,' ',"says \"hello\".");
 
 var fullName = firstName + ' ' + lastName; // this combines two variables and a space between the strings into a new variable
 
 document.write(fullName)
 
 var nameLength = fullName.length; // this calculates the length of the string as an integer
 document.write(nameLength);
 
 var age = 20;
 document.write(fullName + age); // this prints the name string and then the variable (no spaces) 
 
 var ageString = age.toString(); // this converts the age integer variable to a string variable
 document.write(ageString);
 
 /* To convert a string to an integer, the variable must firstly contain ony numbers. It can simply be multiplied by 1 to convert to an integer
 eg. newIntVariable = stringVariable * 1
 or you can use parseInt and parseFloat functions eg parseInt('77');
 */
 
 var message = 'Hello world!';
 document.write(message.indexOf('w')) // the indexOf function finds the index number of a character in a string
 document.write(message.charAt(8)) // this gives the character at index number 8
 document.write(message.length) // this will give the length of the string
 
 var messageArray = new Array();
 messageArray = message.split(' '); //this splits the words (where there is a space) into a new array
 document.write(messageArray[0],"</br>"); // this would return "Hello" (and a new line)
 document.write(messageArray[1]); // this would return "world!"
 
 document.write(message.substring(4,8)); //this will show anything between index number 4 and 8
 document.write(message.substr(4,8)); //substr is different to substring. this will show the 8 characters after index number 4.
 
 document.write(message.toUpperCase()); // converts string to uppercase
 document.write(message.toLowerCase()); // converts string to lowercase
 document.write("<b>",message.toUpperCase(),"</b>"); // this prints the uppercase string in bold using the HTML bold element <b>
 document.write("<h1>This is a heading</h1>"); // HTML elements can be put straight into a string
 </script>
 
</head>
<body>
 
 
</body>
</html>

Next tutorial: Events

JavaScript, Video

Variables and Data Types in JavaScript

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In this second video from the beginners JavaScript tutorial series, you will learn how to create variables and work with strings, integers, and float data types in JavaScript.

Variables are used to store information in program such as text, numbers or true/false values. Variables are given a name and are assigned a value. To create a variable in JavaScript we use the var keyword, then specify the variable name, use the = sign to assign a value, and then specify the value to store (you can also create a variable without immediately assigning it a value). For example: var myNumber = 50;

Variable names must be unique and cannot contain spaces. They don’t begin with a number but can contain numbers. They generally begin with a lowercase letter and if the variable name contains multiple words, then they can be indicated by using camelcase (starting each new word with an uppercase letter) eg. myVariable.

Variables can store data of different types. The main types are:

  • string – text including letters, numbers and other special characters eg. “Hello world”
  • integer – whole number values eg. 5
  • float – numbers with a decimal point eg. 5.3
  • boolean – a true or false value

Watch the video below or click here to view it on YouTube.

The code snippet below shows how to declare variables in JavaScript and how to assign values to a variable. Pay attention to the //comments which explain the different ways of setting up variables.

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="utf-8"/>
 <title>JavaScript - Variables</title>
 <script type="text/javascript">
 
 var myVariable = 50;
 
 // Variable names (identifiers) have to begin with lower or uppercase letters or an underscore
 // Variable names cannot begin with a number, however they can contain a number
 // To declare a variable, use the keyword var
 // You can assign a value to a variable when you declare it, in one line (as above)
 // ...or you can declare a variable and then assign a value later, as below...
 
 var myVariable2;
 myVariable2 = "Hello there";
 
 document.write(myVariable);
 // This displays the value of myVariable in the browser window
 
 </script>
 
</head>
<body>
 
 
</body>
</html>

This source code shows how create and use variables of different data types. Strings are text (letters, numbers and characters), integers are regular whole numbers (treated as numbers), and floats are real numbers (with decimal places eg. 4.5). Boolean is another data type which is used for true/false values. You’ll also see how to use the HTML br tag to add a new line between text that is displayed in the browser.

<!DOCTYPE html>
<html lang="en"
<head>
 <meta charset="utf-8"/>
 <title>JavaScript - Data Types</title>
 <script type="text/javascript">
 //integer
 var age = 20;
 document.write(age);
 
 //float
 var price = 12.95;
 document.write(price);
 
 //string
 var name = "Smith";
 var sentence = "He said \"hello\".";
 
 /*
 Just like in Python, a backslash can be used as an escape character so that
 quotation marks can be used inside a string without any errors
 You can also use single quotes to enclose a string if you want to use double quotes inside a sting
 eg. var sentence = 'He said "hello".';
 */
 
 document.write("</br>", sentence);
 //You can concatenate (join) strings using a comma and you can also use HTML tags inside quotation marks eg. </br>
 //The </br> tag is used to add a new line when the string is displayed in the browser.
 
 </script>
 
</head>
<body>
 
 
</body>
</html>

Hint: Have a look at the toFixed() method if you wish to display floats with a specified number of decimal places.

Next tutorial: Operators