| **Navigation:**  [[introduction.htm|Language Reference]] > 12 - Execution Control > Control Structures >====== CASE (selective execution structure) ====== | [[accept  the event processor .htm|{{btn_prev_n.gif|Previous page}}]][[introduction.htm|{{btn_home_n.gif|Return to chapter overview}}]][[execute  statement execution structure .htm|{{btn_next_n.gif|Next page}}]] |
|  ||

** **

**CASE** //condition//

**OF** //expression// [** TO** //expression //]

//statements//

[** OROF** //expression// [** TO** //expression //] ]

//statements//

[** ELSE **]

//statements//

**END**

{{blk2blue.jpg|blk2blue.jpg}}

| **CASE** | Initiates a selective execution structure. |
| //condition// | A numeric or string variable or expression. |
| **OF** | The //statements// following an **OF** are executed when the //expression// following the OF option is equal to the //condition// of the CASE. There may be many OF options in a CASE structure. |
| //expression// | A numeric or string constant, variable, or expression. |
| **TO** | **TO** allows a range of values in an OF or OROF. The //statements// following the OF (or OROF) are executed if the value of the //condition// falls within the inclusive range specified by the //expressions//. The //expression// following OF (or OROF) must contain the lower limit of the range. The //expression// following TO must contain the upper limit of the range. |
| **OROF** | The //statements// following an **OROF** are executed when either the //expression// following the OROF or the OF option is equal to the //condition// of the CASE. There may be many OROF options associated with one OF option. An OROF may optionally be put on a separate line. An OROF does not terminate preceding //statements// groups, so control "falls into" the OROF //statements//. |
| **ELSE** | The //statements// following **ELSE** are executed when all preceding OF and OROF options have been evaluated as not equivalent. ELSE is not required; however, when used, it must be the last option in the CASE structure. |
| //statements// | Any valid Clarion executable source code. |

A **CASE** structure selectively executes the first set of //statements// encountered for which there is equivalence between the //condition// and //expression// or range of //expressions//. CASE structures may be nested within other executable structures and other executable structures may be nested within CASE structures. The CASE structure must terminate with an END statement (or period).

For those situations where the program's logic could allow using either a CASE structure or a complex IF/ELSIF structure, the CASE structure will generally generate more efficient object code. EXECUTE generates the most efficient object code for those special cases where the condition evaluates to an integer in the range of 1 to n.

Regarding the use of the OF-TO and OROF-TO clauses, //both// expressions are evaluated even if the value of the CASE-expression is less than the lower boundary of the specified range.

For example:

**  CASE A**

**  OF Func1() TO Func2()**

**   ...**

**  END**

In this case, both **Func1()** and **Func2()** are called even if **A <; Func1().**

**Example:**

**CASE**** ACCEPTED()                 !Evaluate field edit routine**

**OF ?Name                        !If field is Name**

** ERASE(?Address,?Zip)           !erase Address through Zip**

** GET(NameFile,NameKey)          !get the record**

** ****CASE**** Action                    !Evaluate Action**

** OF 1                           !adding record - does not exist**

**  IF NOT ERRORCODE()            !should be a file error**

**   ErrMsg = 'ALREADY ON FILE'   !otherwise display error message**

**   DISPLAY(?Address,?Zip)       !display address through zipcode**

**   SELECT(?Name)                !re-enter the name**

**  END        **

** OF 2 OROF 3                    !change or delete - record exists**

**  DISPLAY(?Address,?Zip)        !display address through zipcode**

** ****END****                            !end case action**

** ****CASE**** Name[1]                   !Get first letter of name**

** OF 'A' TO 'M'                  !Process first half of alphabet**

** OROF 'a' TO 'm'**

**  DO FirstHalf**

** OF 'N' TO 'Z' OROF 'n' TO 'z'  !Process second half of alphabet**

**  DO SecondHalf**

** ****END****                            !End case sub(name**

**OF ?Address                     !If field is address**

** DO AddressVal                  !call validation routine**

**END****                             !End case accepted()**

**See Also:**

[[execute  statement execution structure .htm|EXECUTE]]

[[if  conditional execution structure .htm|IF]]