Variable types introduction

Posted On 2009-12-30 by FortyPoundHead
Tags: Tutorial VB6 Miscellaneous General 
Views: 2061

Variables provide temporary storage for information that will be needed during the lifespan of the computer program (or application). This article is short reference table of the types of variables used in programming.

Variables are also used in programming to transfer information from one part of the program to another - for example to provide a place to lay out a document before printing it - as well as being a place to store status information that might be needed by all parts of that program.

While some of the concepts might seem language-specific, they apply to all programming languages to varying degrees, and the terminology is programming language-neutral.

A programmer can imagine a variable as being a box into which information can be placed, and the shape of the box (the variables type) determines what kind of information it can store.

Numeric Data Types
Type Size Range of Values Prefix Example Variable Name
Byte 1 byte 0 to 255 byt bytFirstChar
Integer 2 bytes -32,768 to 32,767 int intCount
Long 4 bytes -2,147,483,648 to 2,147,483,648 lng lngHwnd
Single 4 bytes Negative values: -3.402823E+38 to -1.401298E-45
Positive values: 1.401298E-45 to 3.402823E+38
sng sngPi
Double 8 bytes Negative values: -1.79769313486232e+308 to -4.94065645841247E-324
Positive values: 4.94065645841247E-324 to 1.79769313486232e+308
dbl dblAngle
Currency 8 bytes -922,337,203,685,477.5808 to 922,337,203,685,477.5807 cur curTotalCost

Non-numeric Data Types
Type Size Range of Values Prefix Example Variable Name
String Length of string 1 to 65,400 characters (fixed length) str strName
String Length + 10 bytes 0 to 2 billion characters (variable length) str strHTML
Date 8 bytes January 1, 100 to December 31, 9999 dtm dtmBirth
Boolean 2 bytes True or False bln blnToggle
Object 4 bytes Any embedded object obj objCurrent
Variant 16 bytes Any value as large as Double (numeric) vnt vntNumber
Variant Length+22 bytes Same as variable-length string (text) vnt vntName

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