Constants Constants
A constant is a data object containing a value which you fix at initialization. Constants cannot be changed during the execution of the program.
You declare constants in your program with the CONSTANTS statement (see
The CONSTANTS Statement). If you try to change the constant elsewhere in the program, either the syntax check or the runtime system outputs an error message.You can also declare constants in
type groups in the ABAP Dictionary. 
Use constants if you need a specific value frequently in your program. In this case, do not use literals. If it becomes necessary to modify this value, you only have to change the declaration.
CONSTANTS PI TYPE P DECIMALS 10 VALUE '3.1415926536'.
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