Data Types, Operators, and Control Structures in Programming
Data in Programming: Constants and Variables
Data can behave in two different ways in a program:
- Constants: Their value never changes during the execution of the program.
- Variables: Their value varies as often as necessary.
Naming Conventions
When naming a variable or constant, keep in mind:
- You can use any alphanumeric character, but it must always begin with a letter.
- Spaces are not allowed; use the underscore character for compound names (e.g.,
my_variable). - Name length may not exceed 32 characters.
- Do not use dots or other special characters, nor language keywords (e.g.,
text,caption).
Basic Data Types
- String: Textual data.
- Integer: Whole numbers.
- Long Integer: Larger whole numbers.
- Decimal: Single-precision floating-point numbers.
- Double: Double-precision floating-point numbers.
- Date and Time: Represents dates and times.
- Date: Represents dates.
Variable declaration is typically done using a keyword like dim. If you declare a variable without defining the type, the program automatically assigns the type variant.
The print function displays literal texts and the values of variables.
The value of a constant cannot be modified during the execution of the program.
Data Type Characters
- String:
$ - Integer:
% - Long Integer:
& - Decimal:
!
Arithmetic Operators
| Operator | Symbol | Description |
|---|---|---|
| Sum | + | Calculates the sum of two or more variables. |
| Difference | - | Calculates the difference between two values. |
| Multiplication | * | Multiplies the value of the variables. |
| Division | / | Calculates the value of the division of two numerical values. |
| Exponentiation | ^ | Calculates the value of a variable raised to the power of another. |
| Quotient of Division | / | Calculates the quotient of the division of two numerical values. |
| Remainder of Division | mod | Calculates the remainder of the division between two values. |
Scope of Variables
| Scope | Location | Description |
|---|---|---|
| Procedure | At the beginning of the procedure | Variables are available only within the procedure. |
| Form | In the general declarations section of the form | Variables may be used in all procedures within the form. |
| Application | In the general declarations section of the form, using public instead of dim | Variables declared as public may be used in any form of the application, but their location must be specified when used. |
Control Structures
- Sequential Structures: Allow the execution of the program to be conducted in a specific order. Statements are written sequentially, one after another, in the order they should be interpreted.
- Selective Structures: Used to make logical decisions. Also known as alternative or decision structures. A condition is evaluated, and depending on its outcome, one or another action is performed.
- Repetitive Structures: Also called loops, these structures repeat a sequence of statements a specified number of times.
Iteration: Execution of all actions or instructions that form a loop.
If Statement
Evaluates a condition and, if met, executes a series of specific instructions. Otherwise, the program will continue with other alternative instructions.
Logical Operators
| Operator | Symbol | Description |
|---|---|---|
| AND | and | Requires all conditions in the expression to be true for the expression to be true. If any condition is false, the expression is false. |
| OR | or | The expression is true if at least one of the conditions is true. The expression is false only if none of the conditions are met. |
| NOT | not | The expression is true when the condition is false, and false when the condition is true. |