Читать книгу Excel 2019 Power Programming with VBA - Michael Alexander, Dick Kusleika - Страница 143

VBA makes life easy for programmers because it can automatically handle all the details involved in dealing with data. Some programming languages, however, are strictly typed, which means that the programmer must explicitly define the data type for every variable used.

Data type refers to how data is stored in memory—as integers, real numbers, strings, and so on. Although VBA can take care of data typing automatically, it does so at a cost: slower execution and less efficient use of memory. As a result, letting VBA handle data typing may present problems when you're running large or complex applications. Another advantage of explicitly declaring your variables as a particular data type is that VBA can perform some additional error checking at the compile stage. These errors might otherwise be difficult to locate.

Table 3.1 lists VBA's assortment of built-in data types. (Note that you can also define custom data types, which are covered later in this chapter in the section “User-Defined Data Types.”)

TABLE 3.1 VBA Built-in Data Types

Data Type	Bytes Used	Range of Values
Byte	1 byte	0 to 255.
Boolean	2 bytes	True or False.
Integer	2 bytes	–32,768 to 32,767.
Long	4 bytes	–2,147,483,648 to 2,147,483,647.
Single	4 bytes	–3.402823E38 to –1.401298E-45 (for negative values); 1.401298E-45 to 3.402823E38 (for positive values).
Double	8 bytes	–1.79769313486232E308 to –4.94065645841247E-324 (negative values); 4.94065645841247E-324 to 1.79769313486232E308 (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 with no decimal point; +/–7.9228162514264337593543950335 with 28 places to the right of the decimal.
Date	8 bytes	January 1, 0100 to December 31, 9999.
Object	4 bytes	Any object reference.
String (variable length)	10 bytes + string length	0 to approximately 2 billion characters.
String (fixed length)	Length of string	1 to approximately 65,400 characters.
Variant (with numbers)	16 bytes	Any numeric value up to the range of a double data type. It can also hold special values, such as Empty, Error, Nothing, and Null.
Variant (with characters)	22 bytes + string length	0 to approximately 2 billion.
User-defined	Varies	Varies by element.