Learn VB Script Part 3

Data Types

What Are VBScript Data Types?

VBScript has only one data type called a Variant. A Variant is a special kind of data type that can contain different kinds of information, depending on how it's used. Because Variant is the only data type in VBScript, it's also the data type returned by all functions in VBScript.

At its simplest, a Variant can contain either numeric or string information.

       A Variant behaves as a number when you use it in a numeric context and as a string when you use it in a string context. That is, if you are working with data that looks like numbers, VBScript assumes that it is numbers and does what is most appropriate for numbers. Similarly, if you're working with data that can only be string data, VBScript treats it as string data. You can always make numbers behave as strings by enclosing them in quotation marks (" ").

Variant Subtypes

Beyond the simple numeric or string classifications, a Variant can make further distinctions about the specific nature of numeric information. For example, you can have numeric information that represents a date or a time. When used with other date or time data, the result is always expressed as a date or a time.

You can also have a rich variety of numeric information ranging in size from Boolean values to huge floating-point numbers. These different categories of information that can be contained in a Variant are called subtypes. Most of the time, you can just put the kind of data you want in a Variant, and the Variant behaves in a way that is most appropriate for the data it contains.

The following table shows subtypes of data that a Variant can contain. 

Subtype	Description
Boolean	Logical value: true (numeric value is "nonzero", mostly -1) or false (numeric value is 0) See the notes below.
Byte	Integer value (1 byte) in the range: 0 to 255.
Integer	Integer value (2 bytes) in the range: -32,768 to 32,767.
Long	Integer value (4 bytes) in the range: -2,147,483,648 to 2,147,483,647.
Single	Real value (4 bytes) with the precision 7 digits in the range: -3.402823E38 to -1.401298E-45 for negative values. 1.401298E-45 to 3.402823E38 for positive values. Binary implementation format is according to standard IEEE-754 (32-bit)
Double	Real value (8 bytes) with the precision 15 digits in the range: -1.79769313486232E308 to -4.94065645841247E-324 for negative values. 4.94065645841247E-324 to 1.79769313486232E308 for positive values. Binary implementation format is according to standard IEEE-754 (64-bit)
Date	Value containing Date and time. See the notes below.
String	variable-length string that can be up to approximately 2 billion characters in length in the Unicode character set.
Object	"pointer" (reference) to any object.
Array	Array of values. See How to use array of values in the PROMOTIC system.
Empty	Flag that value is uninitialized.
Null	Flag that value intentionally contains no valid data.

Numeric data types Byte, Integer and Long:

Entering the values with hexadecimal constant:

It is possible to enter a number into the variable in decimal figure, for example:
nVal = 36524

or in hexadecimal figure, where the &h prefix is used, for example:
nVal = &h8EAC


(8EAC hexadecimly is 36524 decimaly). But the VBScript evaluates the hexadecimal constants the following way: if the constant is two byte (like we have here), then it creates Integer data type. Because the value 8EAC has the highest bit set, then the constant will be considered as negative numberequal to -29012!

Boolean data type:

Value of the Boolean type can logicaly have just two states (true / false), but it is actually stored asInteger data type and it is supposed that false is zero and true is non-zero.

And this way of understanding the true value can cause trouble, because by default the value is -1, but also any other non-zero value is also true !! That is why we do not recommend comparing the truevalues.

Example:

If value = true Then ...

Date data type:

If the value of the date/time is stored as Date data type, then the values of year/month/day/hour/minute/second can be obtained, for example, by the VBScript methods Year/Month/Day/Hour/Minute/Second. See also VBScript date and time functions and Pm date and time methods.

Date creating from String data type:

The required date (time, date and time) must be written into quotation marks in the format specified in Windows settings "Control Panel / Date/Time / Date and time page". For example, if the date is set in the format d.M.yyyy in the local setting, then the time can be entered as String in the following way:

Dim MyTime, MyDate, MyDateTime

MyTime = CDate("18:59:33")

MyDate = CDate("31.12.2015")

MyDateTime = CDate("31.12.2015 18:59:33")

Date creating by the VBScript constant:

If the date (time, date and time) is entered by this way, it doesn't depend on setting the computer and the date (time, date and time) will always be in the correct format. The date (time, date and time) is entered by the # char in the format #dd/mm/yy# (or #hh:mm:ss# or #dd/mm/yy hh:mm:ss#):

Dim MyTime, MyDate, MyDateTime

MyTime = #18:59:33#

MyDate = #23/10/05#

MyDateTime = #23/10/13 18:59:33#

Date creating from real number:

The date (year, month, day) is represented by the whole part of the real number.

It is a number of days since 30.12.1899. Value 1.0 refers to the date 31.12.1899, value –1.0 refers to the date 29.12.1899.

The time (hours, minutes, seconds) is represented by the decimal part of the real number. The value x.5 means the exact midday (12:00:00) in the day x.

The value from 0.0 to 1.0 is a special case. The value is not considered to be a date but only as time or time range. The value 0.5 represents 12 hours, 1/24/60 represents 1 minute.

The following script assigns the value of the date and the time greater by one day and by one minute into the variable MyDateTime on each execution of the script.

MyDateTime = CDate(MyDateTime + 1 + 1/24/60)

If the variable MyDateTime is initialized by value 1, then after the first execution of the script, the value of the variable equals to "1.1.1900 0:01:00", after the second execution, it equals to "2.1.1900 0:02:00".