Lecture 5Assigning Values, Calculations, Conversions, Control Statements, Debugging

BCO5647 Applications Programming Techniques (ABAP)

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Readings & Objectives

Readings

Keller & Kruger Chapter 4 Section 4.3Chapter 2 Section 2.3.8

Objectives

This lecture will

Introduce the Input Parameter

Explore changing variables by copying and initialisation

Examine how calculations can be made in ABAP

Examine Control Statements and Logical Expressions in ABAP

Explore Debugging techniques in ABAP via the Debug Function

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Input Parameters

A Parameter is a special type of variable. It requires the value of the variableto be input from a selection screen.

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Input Parameters

report lec401.

tables: spfli.

parameters: carr like spfli-carrid

default ‘LH’.

select * from spfli

where carrid = carr.

write: / spfli-carrid, spfli-connid,

spfli-cityfrom, spfli-cityto.

endselect.

if sy-subrc <> 0.

write / 'no records found'.

endif.

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Input Parameters

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Changing variables: copy & initialisation

You can set a start value for an elementary field yourself using the VALUE addition.

You can copy the field contents of a data object to another data object with the MOVE statement. Ifthe two data objects have different types, the type is automatically converted if there is aconversion rule.

The CLEAR statement resets the field contents of a variable to the initial value for the particular type.

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Changing variables: Initialisation

The CLEAR statement sets the value of a variable or a structure tozeros. If the data type is c, the value is instead set to blanks.

data: a1(2) type c value ‘AB’,a2 type i value 123,

a3 type p value 12345,a4(3) type n value ‘789’,a5 type d value ‘19990112’,a6 type t value ‘1330’,begin of g1, a1(3) type c value ‘ASD’, a2 type i value 123,

end of g1.

clear: a1, a2, a3, a4, a5, a6,g1-a1 with ‘X’,g1-a2.

write: a1, a2, a3, a4, a5, a6, g1-a1, g1-a2.

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Calculations

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Calculations

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Conversion Rules: Elementary Types

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Calculations with dates

NNN

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Control Statements

ABAP has 2 conditional logic statements:

If/Endif and Case/Endcase

2 loops: Do/Enddo While/Endwhile

and others such as Continue, Check & Exit.

ABAP does not have a GOTO statement.

Control commands can be nested and/or joined with logical operators.

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Logical Expressions

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Conditions: If / ElseIf

Syntax: if logical expression #1.

command lines.[elseif logical expression #2.

command lines.][else.

command lines.]endif.

Examples.

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Logical Expressions & Operators

IF statements may be joined using the AND, OR or NOT operators. Logical expressions may use the following comparative operators :

eq = ne <> ><gt > ge >=lt < le <=betweenco, ca, cs, cp (string comparisons)

Examples.

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Evaluating Field Contents: Case/EndCase Vs If/Endif

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Loops : Do/EndDo

An unconditional loop.

Syntax : do [N times].Commands.

enddo.

The [N times] parameter is optional. How do you end the loop ?

A system field, sy-index, automatically stores the number of the current looppass.

Examples.

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Loops : While/EndWhile

Loop with terminating condition.

Syntax : while logical expressioncommands

endwhile

While the logical expression is true, the sequence of commands isexecuted.

Examples.

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Other control commands

The CONTINUE statement inside a loop bypasses all subsequent statementswithin the loop and forces the next loop to begin.

The CHECK statement has the same effect as CONTINUE if the specifiedlogical expression is not true.

The EXIT statement within a loop structure stops the processing of the loopand the program will continue after ENDDO/ENDWHILE.

Examples.

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Debugging a program

To investigate runtime errors, ABAP has a simple and efficientdebugging facility which allows you to :

set breakpoints and stop the program during runtime.continue statement by statement.skip over subroutines.view and change the contents of variables.

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Debugging Mode

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Breakpoints in Debugging Mode