Forces all variables used to be defined and properly typed. VB is not strongly typed so it's kinda of easy to get "spaghetti" code going. This helps to cut down on it. Also helps the user instantly find typos in variable names.
Option Base [0|1]
Option Compare [Binary | Text]
Option Private Module
Form 1: Set the default base index for array declarations. Affects Dim, Static, Private, Public and ReDim. Does not affect Array, ParamArray or arrays declare in a Type. Option Base 0 is the default.
Form 4: Public symbols defined by the module are only accessible from the same project.
Option Base 1 Option Explicit Sub Main Dim A Dim C(2) ' same as Dim C(1 To 2) Dim D(0 To 2) A = 1 B = 2 ' B has not been declared End Sub