VBA Statement - Sub, Private Sub, Public Sub

Sub statement is subroutine also known as Procedures or Macros (When we record macro the default name is Sub Macro1() follow by series of code and close with End Sub. Macro1 is the default name of procedure recorded. Same case when we create on our own.we start with Sub Procedure Name() and Close with End Sub.

Syntax :
Sub Procedure Name (ArgList)
    Statements (Code)
    Exit Sub
    Statements (Code)
End Sub

Actually the syntax consist many optional parts but required only 3 which is Sub, Procedure name and End Sub to explain in detail refer below:

Case Study 1: 

Sub Procedure Name ()
    Statements (Code)
    Call another Procedures
    Exit Sub
    Statements (Code)
    Call another Procedures
End Sub

This is the most typical of Sub Statement, it can be accessible from anywhere in the project and listed in macros and can run directly.

Case Study 2: 

Sub Procedure Name (ByVal and ByRef Variables)
    Statements (Code)
    Call another Procedures
    Exit Sub
    Statements (Code)
    Call another Procedures
End Sub

This Sub Statement only can be access from another Sub Statement in the project because we need to specify variables inside open and close bracket and not listed in macros.

Case Study 3: 

Public Sub Procedure Name ()
    Statements (Code)
    Call another Procedures
    Exit Sub
    Statements (Code)
    Call another Procedures
End Sub

This Sub Statement same as typical Sub Statement above, it can be accessible from anywhere in the project and listed in macros and can run directly.

Case Study 4: 

Private Sub Procedure Name ()
    Statements (Code)
    Call another Procedures
    Exit Sub
    Statements (Code)
    Call another Procedures
End Sub

This Sub Statement only can be access from another Sub Statement within the same module and not listed in macros.

Note:

1. There are another Sub which Friend Sub (only class module) and Static Sub (preserved variables) but seldom use for beginner.
2. The procedure name must be related with the macro task to ease accessible process and there are rules to follow ex. no space, certain characters and etc.

Read more about Sub statement, macro enabled excel, excel macro,
vba coding, vba code at below links.

Microsoft Reference-Sub-statement
Other Reference-Subroutines

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