1. Subroutines and Functions
MINS298c
Fall 1998
Chapters 10
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Subroutines

2. Overview Subroutines Forms Functions What they are
Why to include in program
Forms
Implementing and using
Functions
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Subroutines

3. Scope of the Program
Global: Applies to all programs or parts of programs running at the time
Not advised if can be avoided
Prone to errors
Difficult to track
Local: Applies to only the subprogram running at the time
Increases modularity of code (good thing)
Easy to debug and track
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Subroutines

4. Subroutines (Normal Scope)
Line
Program
DATA A, B, C 1 2 3 4 5 6
According to normal
rules of “scope,” which
Write statements are
legal and which are not?
Write A
Write F
Form
DATA X, Y, Z
Write A
Write F
Form
DATA D, E, F
Write A
Write F
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Subroutines

5. Subroutine
Self contained blocks of code that can be reused by different parts of a program
Advantages:
Self contained code = Easy to maintain and debug
Changes in subroutine do not affect rest of program
Reduces complexity -- more modular
Consistent with code quality: Highly Cohesive Loosely Coupled
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Subroutines

6. Mapping ABAP Concepts to Subroutines
Subroutine = Form
Explicit to program by being a block of code within the program
Implicit to program by using INCLUDE
Both are called using PERFORM
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Subroutines

7. Subroutines Defined by FORM and ENDFORM Executed with PERFORM verb
Can call by value or call by reference
by reference is implied
VALUE clause passes by value
ABAP does number and type checking at runtime
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Subroutines

8. PERFORM Syntax PERFORM subroutine_name
[USING p1 p2 p3….]
[CHANGING p1 p2 p3 …]
[TABLES itab1 itab2 itab3 …..]
USING passes p1, p2, … pn single variables by reference
USING VALUE p1 p2 …p3 passes values to subroutine but return values do not replace original p1, p2, pn
Example of use: depreciation or tax calculation changes original value of asset during calculation
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Subroutines

9. PERFORM Syntax cont. CHANGING nearly the same as USING
Values are changed in the subroutine
Passed back to the calling program, but changes are not passed back until the subroutine ends
TABLES passes a whole table(s) by reference
Uses internal table(s)
Can not pass by Value only Reference ??
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Subroutines

10. Example ASSUME: x, y, and z are integer and x = 4; y = 5; z =10
WRITE x, y, z.
PERFORM add_em CHANGING VALUE(x) y CHANGING z.
FORM add_em a1 a2 CHANGING a3.
a1 = a1 + 1.
a2 = a2 + 2.
a3 = a1 + a2.
ENDFORM..
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Subroutines

11. Functions
Functions are global -- available to all programs from the library: Created outside the program
Created with FUNCTION and ENDFUNCTION statement
Called from programs with CALL FUNCTION
ABAP/4 Development Workbench > Function Group Objects > Single Object
Name the function and click on Create
Parameters of a function = Import, Export, Change
See pages
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Subroutines

12. Programming Assignment 2
Write a program to create a list of the top five companies with the highest sales
Use SAP Table TABNA and pick up country, name of company, address, sales, and currency
Call the function CONVERT_TO_LOCAL_CURRENCY properly
Transfer conversion date, foreign currency amount, foreign currency key, and target currency key
Use a subroutine to rank the companies by sales where we can get the top N companies
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Subroutines