---
title: "Program Flow Logic"
slug: "program-flow-logic"
updated: 2024-01-30T14:19:24Z
published: 2024-01-30T14:19:24Z
canonical: "kb.dataparc.com/program-flow-logic"
---

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# Program Flow Logic

Allows conditional execution, based on the evaluation of an expression.

**Syntax 1: If** *condition* **Then** *thenpart* [ **Else** *elsepart*]

**Syntax 1 Remarks:** The single-line form is often useful for short, simple conditional tests. Syntax 1 has these parts:

| **Part** | **Description** |
| --- | --- |
| **If** | Begins the simple **If...Then** control structure. |
| *Condition* | One of two types of expressions: A numeric or string expression that evaluates true (nonzero) or false (0 and **Null**) **.** |
| **Then** | Identifies actions to be taken if *condition* is satisfied. |
| *Thenpart* | Statements or branches performed when *condition* is true |
| **Else** | Identifies actions taken if *condition* is not satisfied. If the **Else** clause is not present, control passes to the next statement in the program. |
| *Elsepart* | Statements or branches performed when *condition* is false |

**Syntax 2**

**If** *condition1* **Then** [ *statementblock-1*] [ **ElseIf** *condition2* **Then** [ *statementblock-2*] ] [ **Else** [ *statementblock-n*] ] **End If**

**Syntax 2 Remarks:** The block form of **If...Then...Else** provides more structure and flexibility than the single-line form and is usually easier to read, maintain, and debug. Syntax 2 has these parts:

| **Part** | **Description** |
| --- | --- |
| **If** | Keyword that begins the block **If...Then** decision control structure. |
| *Condition1* | Same as *condition* used in the single-line form shown above. |
| **Then** | Keyword used to identify the actions to be taken if a condition is satisfied. |
| *Statementblock-1* | One or more Visual Basic statements executed if *condition1* is true |
| **ElseIf** | Keyword indicating that alternative conditions must be evaluated if *condition1* is not satisfied. |
| *Condition2* | Same as *condition* used in the single-line form shown above. |
| *Statementblock-2* | One or more Visual Basic statements executed if *condition2* is true |
| **Else** | Keyword used to identify the actions taken if none of the previous conditions are satisfied. |
| *Statementblock-n* | One or more Visual Basic statements executed if *condition1* and *condition2* are both false. |
| **End If** | Keyword that ends the block form of the **If...Then**. |

In executing a block **If**, Visual Basic tests *condition1*: the first numeric expression. If the expression is true, the statements following **Then** are executed.

If the first expression is, Visual Basic begins evaluating each **ElseIf** condition in turn. When Visual Basic finds a true condition, the statements immediately following the associated **Then** are executed. If none of the **ElseIf** conditions is true, the statements following the **Else** are executed. After executing the statements following **Then** or **Else**, the program continues with the statement following **End If**.

The **Else** and **ElseIf** clauses are both optional. There is no limit to the number of **ElseIf** clauses in a block **If**, but none can appear after an **Else** clause. Any of the statement blocks can contain nested block **If** statements. The block **If** must end with an **End If** statement.

Example: This example calculates the ratio of two input tags, depending on which is larger. If they are equal, the ELSE statement is executed.

If GD(1) > GD(2) Then

Result = GD(2)/GD(1)

ElseIf GD(2) > GD(1) Then

Result = GD(1)/GD(2)

Else

Result = 1

End If