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In everyday life, we have to deal with all kinds of information and data. For example, we need to deal with data like names, money, phone number, addresses, date, stock quotes and more.
Similarly, in Visual Basic 2017, we have to deal with all sorts of data, some of them can be mathematically calculated while some are in the form of text or other non-numeric forms. In Visual Basic 2017, data can be stored as variables, constants or arrays. The values of data stored as variables always change, just like the contents of a mailbox or the storage bin while the value of a constant remains the same throughout.
8.1 Visual Basic 2017 Data Types
Visual Basic 2017 classifies information into two major data types, the numeric data types, and the non-numeric data type
8.1.1 Numeric Data Types
In Visual Basic 2017, numeric data types are types of data comprises numbers that can be calculated using various standard arithmetic operators. Examples of numeric data types are examination marks, height, body weight, the number of students in a class, share values, the price of goods, monthly bills, fees, bus fares and more. In Visual Basic 2017, numeric data are classified into seven types based on the range of values they can store. Numeric data that involve round figures are classified as Integer or Long integer. Data that require high precision calculation are classified as single and double precision data types, they are also called floating point numbers. Numeric data that involve money are classified as currency data types. Lastly, data that require more precision and involve many decimal points are classified as decimal data types. These data types are summarized in Table 8.1
Table 8.1: Numeric Data Types
| Byte | 1 byte | 0 to 255 |
| Integer | 2 bytes | -32,768 to 32,767 |
| Long | 4 bytes | -2,147,483,648 to 2,147,483,648 |
| Single | 4 bytes | -3.402823E+38 to -1.401298E-45 for negative values 1.401298E-45 to 3.402823E+38 for positive values. |
| Double | 8 bytes | -1.79769313486232e+308 to -4.94065645841247E-324 for negative values 4.94065645841247E-324 to 1.79769313486232e+308 for positive values. |
| Currency | 8 bytes | -922,337,203,685,477.5808 to 922,337,203,685,477.5807 |
| Decimal | 12 bytes | +/- 79,228,162,514,264,337,593,543,950,335 if no decimal is use +/- 7.9228162514264337593543950335 (28 decimal places). |
8.1.2 Non-numeric Data Types
In Visual Basic 2017, non-numeric data types are data that cannot be calculated using standard arithmetic operators. The non-numeric data comprises text or string data types, the Date data types, the Boolean data types that store only two values (true or false), Object data type and Variant data type.They are summarized in Table 8.2
Table 8.2: Non-numeric Data Types
| Type | Storage | Range |
|---|---|---|
| String(fixed length) | Length of string | 1 to 65,400 characters |
| String(variable length) | Length + 10 bytes | 0 to 2 billion characters |
| Date | 8 bytes | January 1, 100 to December 31, 9999 |
| Boolean | 2 bytes | True or False |
| Object | 4 bytes | Any embedded object |
| Variant(numeric) | 16 bytes | Any value as large as Double |
| Variant(text) | Length+22 bytes | Same as variable-length string |
8.1.3 Suffixes for Literals
Literals are values that you assign to data. In some cases, we need to add a suffix behind a literal so that Visual Basic 2017 can handle the calculations more accurately. For example, we can use num=1.3089! for a single precision data type, num=1.3089# for a double precision data type, num=130890& to indicate long integer data type and num=1.3089@ to indicate currency data type. The suffixes are summarized in Table 8.3.
Table 8.3
| Suffix | Data Type |
|---|---|
| & | Long |
| ! | Single |
| # | Double |
| @ | Currency |
In addition, we need to enclose string literals within two quotations and date and time literals within two # sign. Strings can contain any characters, including numbers. The following are few examples:
memberName=”Turban, John.”
TelNumber=”1800-900-888-777″
LastDay=#31-Dec-00#
ExpTime=#12:00 am#