VISUAL BASIC

VISUAL BASIC

1. The forms are treated as controls with their properties, events and methods. Although we say that it is a special control that uses to control the most common controls with which we will build our applications: text box, label, command button.

   • Forms

2. The Toolbox window shows the controls that you can add to vb projects. To open the Toolbox, choose Toolbox from the View menu.

   • ToolBox

3. The controls are:

4. Properties of objects

5. Control structures

   • Control the flow of the program in a function
     • are
       • IF, WHILE: Condition
       • THEN, ELSE: judgment
       • NEXT, FOR: Variable or counter
       • SELECT: evaluate a condition CASE: They contain values

6. Type of data

   • Boolean: The Boolean has only two states, True and False. These variables are generally used as flags or conditional.
   • Integer: Integer or integer is a 16-bit number that can range between -32768 and 32767. Integers should be used when working with values that can not contain fractional numbers
   • Byte: The Byte corresponds to an 8-bit variable that can store values from 0 to 255. It is very useful for the storage of binary data.
   • Double: The Double is a 64-bit floating-point number that is used when you need high precision. These variables can vary from1.79769313486232E308 to -4.94065645841247E-324 for negative values and 4,94065645841247E-324 to 1.79769313486232E308 for positive values.
   • Long: The Long is a 32-bit number that can vary between -2,147,483,648 and 2,147,483,647. The Long variables can only contain integer values
   • Decimal: The Decimal is a subtype of Variant data, it can store values in a range that goes from -79.228.162.514.264.337.593.543.950.335 to 79.228.162.514.264.337.593.543.950.335 if the value does not contain decimal digits. It has an accuracy of up to 28 decimals with values from - 7.92281625142643375935439503816235 to 7.922514264337593543950335.
   • Single: The Single is a 32-bit number that goes from -3.402823E38 to -1.401298 E-45 for negative values and from 1.401298E-45 to 3.402823E38 for positive values. When fractional numbers are needed within this range, this is the type of appropriate for its use.
   • String: The String is generally used as a type of length for a text string. A variable length string can contain a maximum of approximately 2 billion characters. Each character has a value ranging from 0 to 255 based on the ASCII character set.
   • Currency: The currency data type is actually an integer type. In use, it is scaled by a factor of 10,000 to add four digits to the right of the decimal point. Allow up to 15 digits to the left of the decimal point, resulting in a range of approximately -922,337,000,000,000 to +922,337,000,000,000.
   • Date: The Date stores a numeric value with a special format that represents both the date and the time. The Date accepts the date or time, or both. Possible values range from January 1 of year 100 to December 31 of year 9999.
   • Object: The Object can point to any type of data, including any object instance that the application recognizes. Object is used when at compile time it is not known what type of data the variable can point to. Regardless of the type of data you refer to, an Object variable does not contain the value itself, but a pointer to the value. Because of the code that the pointer uses to search for data, the Object variables are access a bit slower than variables that have an explicit type.
   • Variant: Variants store numeric and non-numeric values. They are the most flexible of all the available types, since they store very large values of almost any type (coincides with the double numeric data type). It is used only when you are not sure of the type or when you are accommodating external data and you are not sure of the specifications of the data type

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