VB Classic is a loosely typed language. Declaring variables is optional unless you use the Option Explicit statement to force explicit declaration of all variables with Dim, Private, Public, or ReDim. Using Option Explicit is strongly recommended to avoid incorrectly typing an existing variable and to avoid any confusion about variable scope.
Undeclared variables are variants. To specifically declare a variant, use:
Dim x As Variant
Common data types include Byte (0..255), Boolean, Integer (2-byte integers), Long (4-byte integers), Currency, Single (32-bit number), Double (64-bit number), Date, String, and variant.
Variables declared with Dim at the module level are available to all procedures within the module. At the procedure level, variables are available only within the procedure.