C#: Convert from decimal to binary

The following program will convert a decimal number (base 10) into it's binary representation (base 2).
To achieve it we need to create:
2 textboxes called txt_dec and txt_bin
1 button called btn_calculate  



En el botón btn_calcular digitar el siguiente codigo:

           
                int dec, bin;
                string out = "";
                dec = Convert.ToInt16(txt_dec.Text);
 

                while (dec > 0)
                {

                    bin = dec % 2;
                    dec = dec / 2;
                    Convert.ToString(bin);
                    out = bin + out;
                    txt_dec.Text = Convert.ToString(out);

                }

                txt_dec.Focus();

Code explanation:

int dec, bin: We declate the variable dec and bin Integer type.

string out = "": We declare the variable out type string which we'll assign the value 'nothing'.

dec = Convert.ToInt16(txt_dec.Text): Here we assign to the dec variable the textbox txt_dec value, at the same time we convert the textbx to Integer type.

while (dec > 0): While the variable dec be greater than 0 then ...

bin = dec % 2: The variable bin will get the value of the operation: the variable dec value % 2. (% means Mod in C#). The Mod is used to obtain a division residue. The division will be between the number we indicate next to the symbol %, this case the number 2, because 2 is the binary numbers base.

dec = dec / 2: After to obtain the first residue the variable dec will get it's own value between 2.

Convert.ToString(bin): We convert the variable bin into String type to achieve the concatenation.

out = bin + out: The variable "out" is going to get the bin's value  (which contain the division residue) concatenated with the same variable "out" to keep accumulating the values of the others residues that generates while the "WHILE" runs.

txt_bin.Text = Convert.ToString(out):Finally we assign to the textbox txt_bin, the value of the variable "out".

JavaScript form validation

This is an example of a form validation using JavaScript. First we create a form in HTML, with the fields Name, Last name and Telephone y two buttons Validate and Clear. We'll assign to each of these HTML elements an id to identify them in the JavaScript code with their respective names.


Ex:
<form>
<label>Name:</label>
<input type="text" id="name" name="name" size="20" autofocus="autofocus" /><br/>
<label>LastName:</label>
<input type="text" id="lastname" name="lastname" /><br/>
<label>Telephone:</label>
<input type="text" id="telephone" name="telephono" /><br/>
<input type="button" value="Validate" id="boton_validate" />
<input type="reset" value="Clear" />
</form>

Then bellow the form we write the JS code:


<script type="text/javascript">

function validate() {
    var name= document.getElementById("name");
    var lastname= document.getElementById("lastname");
    var telephone= document.getElementById("telephone");

    if (name.value.trim() == "") {
        name.focus();
        return alert("There is an empty element");
    } else {
        if (lastname.value.trim() == "") {
            lastname.focus();
            return alert("There is an empty element");
        } else {
            if (telephone.value.trim() == "") {
                telephone.focus();
                return alert("There is an empty element");
            }
        }
    }

}

document.getElementById("validate_button").onclick = validate;

</script>

Code explanation: 

First we create the "validate" function, on it the code that this will return.
We assign to JS variables the HTML inputs. Ex: var name = document.document.getElementById("name");

We ask if the JS variables values are empty then we send the focus to the corresponding input (name.focus();) and we send to screen the message (return alert("There is an empty element");)

Finally we decide that the validate button's name (this case "validate_button", identified by its id in HTML ), the event "onclick" returns "validate" that is the function's name.

Note: The function trim() is used to eliminate white spaces in the begging and ending of a string.

Definitely the full code will look like this:


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

<html>
<head>
<title>JavaScript Form Validation</title>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
</head>


<body bgcolor="#FFFFFF">

<hr />
<h2> JavaScript form validation </h2>
<hr />
&nbsp;

<form>
<label>Name:</label>
<input type="text" id="name" name="name" size="20" autofocus="autofocus" /><br/>
<label>LastName:</label>
<input type="text" id="lastname" name="lastname" /><br/>
<label>Telephone:</label>
<input type="text" id="telephone" name="telephone" /><br/>
<input type="button" value="Validate" id="validate_button" />
<input type="reset" value="Clear" />
</form>

<script type="text/javascript">

function validate() {
    var name= document.getElementById("name");
    var lastname= document.getElementById("lastname");
    var telephone= document.getElementById("telephone");

    if (name.value.trim() == "") {
        name.focus();
        return alert("There is an empty element");
    } else {
        if (lastname.value.trim() == "") {
            lastname.focus();
            return alert("There is an empty element");
        } else {
            if (telephone.value.trim() == "") {
                telephone.focus();
                return alert("There is an empty element");
            }
        }
    }

}

document.getElementById("validate_button").onclick = validate;


</script>


</body>
</html>




Calculate the Area of a Rectangle in DFD

DFD is a simple flowchart editor and simulator program.

To calculate the area of a rectangle is implement the formula a = b * h. Where a is the area, b is the base and h, the height. To run this program we'll use the program DFD. You can download it from here. Note: The software language is Spanish.

First the variables "b" and "h" will be read, as shown in the right image, in a Read object.

Then we'll assign to the "a" constant the resulting value of the operation "b * h". In an Assign object.

Finally in an Output object the value of "a" will be printed.

Multiplication table in Visual Basic 6.0

This program works by inserting a number to a TextBox and when press the "Multiply" button the table multiplication of that number from 1 to 12 is going to appear in the ListBox. In order to do that we're going to user 1 TextBox, 1 Listbox and 1 CommandButton, as shown bellow.

To make this program works we have to tape the following code in your CommandButton, this case called Command1:

Private Sub Command1_Click()

List1.Clear
Dim n As Integer
n = 0
Do While n < 12
n = n + 1
r = Val(Text1.Text) * n
List1.AddItem (Text1.Text & " x " & n & " = " & r)
Loop
Text1.Text = ""
Text1.SetFocus

End Sub

Now explain the code above:

List1.Clear: This is going to, each time the code runs, clean the Listbox.

Dim  n as Integer: Here we declare the variable "n" which stores Integer values.

n= 0: Here we give to the variable "n" the value 0. This way we initialize this variable which must have a value to use the Do While.

Do While n < 12: Here we say while the variable "n" be less than 12 run the code between the Do While and the Loop.

n= n+1: This code will make you add 1 to the variable "n". This way the variable "n" that had a value of 0 is going to plus 1 while the value of "n" be less than 12.

r = Val(Text.Text) * n: "r" es the constant where the value of the multiplication will be stored, the order represents the operation. 

List1.AddItem (Text1.Text & " x " & n & " = " & r): This part is where literally we say to the program to add to the Listbox the value of the TextBox, the letter "x", the value of the variable "n", the = sign and the value of the variable "r". What we are doing here is concatenating the variables and the multiplication signs. The & sign is used in VB 6.0 to concatenate.

Loop: In case of failure to comply the condition settled in the Do While it retuns back, when the condition is met then the Do While ends. 

Text1.Text = "": This will, each time we press the Multiply button, the TextBox value gets clean. 

Text1.SetFocus: Return the cursor to the Text1. 

If we insert the number 2 to the Textbox then this will be the result.

Visual Basic 6.0: Convert from Decimal to Binary

In order to make this program we're going to use two textboxes txt_input and txt_output. And a Commandbuttton cmd_calculate.

The following is the complete code to make the program works:

Dim dec, bin As Integer
Dim out As String


Private Sub cmd_calculate_Click()

dec = Val(txt_input.Text)
out = ""


While dec > 0

bin = Fix(dec) Mod 2
dec = Fix(dec) / 2
out = bin & out
txt_output.Text = Val(out)

Wend

txt_output.SetFocus

End Sub

  


Code explanation:

Dim dec, bin As Integer: Here we declare the variables dec and bin as type integer.

Dim out As String: Here we declare the variable out as type string, it means just text.

dec = Val(txt_input.Text): We assign to the variable dec the value of the textbox txt_input while the function "Val" converts the textbox in integer type.

out = "": We initialize the variable out with an empty value.

While dec > 0: While the variable dec be greater than 0 then...

bin = Fix(dec) Mod 2: The variable "bin" value is going to be the variable "dec" Mod 2 value... The Mod is used to obtain the residue of a division. The division is going to be between the number we indicate next it, this case the number 2, by being the number 2 the base of the binary numbers.  

dec = Fix(dec) / 2:  After obtaining the first residue the variable "dec" is going to get itself value between 2. 

out = bin & out: The variable "out" value is going to be the variable "bin" value (the one that contains the division residue value) concatenate with the the same variable "out" to accumulate the value of the other residues generated while running the "WHILE".


txt_output.Text = Val(out) :  Finally we assign to the textbox txt_output the value of the variable "out".

Wend: Here is where the "WHILE" ends and returns up while the specified condition is met. 


*Notes: 

Funcion Val: Returns the contained numbers in a string as a number value of appropriate type.

Funcion Fix: Return the integer portion of a number.
& : Is used to concatenate characters.