Order of ABAP Events

Although there are subroutine that makes our code easier to maintain by modularize the program into modular units or logical blocks. There are some default blocks that help in controlling the flow of the program. These blocks are known as there are some ABAP events and they run in sequence.



LOAD-OF-PROGRAM
The first triggered event is load-of-program that runs before any other ABAP code. The purpose is to load the program into system memory so that the program can be executed. However, this event only available for program with the type of 1, M, F, or S.

INITIALIZATION.
Initialization will be the next event after Load-Of-Program. But, it will be the first triggered event if the program does not have load-of-program event. This event allow us to initialize values of variables or input fields of the selection screen.

AT SELECTION-SCREEN.
Before the selection screen is displayed, this event is usually called to validate done on selection screen. Moreover, it can be used to manipulate the actual screen in order to make a dynamic selection screen that can hide/disable some parameter by the use of loop at screen funcion.

START-OF-SELECTION.
This event is the first event that is triggered right after the user executes the program by pressing execute button (F8). It is before any GET events or any other event processing blocks. This will be started automatically when there is no other event keywords coded.

END-OF-SELECTION.
This event is triggered after all logical database records have been read or once the START-OF-SELECTION is finished. The purpose of this is generally only for the summary/results of reports.

TOP-OF-PAGE.
This event is used on basic list only in order to create a header.

END-OF-PAGE.
On the contrary, this event is used to create a footer.

AT LINE-SELECTION.
After the screen list has been displayed, the user can select on a list line by double click it or F2 to display a secondary list.

AT PFn (n is number between 01-24)
This is the event which is triggered by function key to perform interactive action.

AT USER-COMMAND.
This event triggered when toolbar button is pushed.



Source:
http://saptechsrs.blogspot.co.id/2011/10/abap-events-in-report-programming.html
http://loveabap.blogspot.co.id/2012/04/abap-flow-of-events-1.html
http://www.sapdev.co.uk/abap/abap-events.htm

ABAP Editor Keyboard Shortcuts

Icon	Shortcut Key	Use
	Enter key	Enter/Continue
	Ctrl S	Save
	F3	Back
	Shift F3	Exit System Task
	F12	Cancel
	Ctrl P	Print
	Ctrl F	Find
	Alt F12(PC only)	Customize local layout
	Ctrl G	Continue Search
	F1	Help
	Ctrl Page Up	Scroll to top of document
	Page up	Scroll up one page

Variable Naming Convention in ABAP

Here are some rules that I used for my convenience in coding ABAP. You can also have your own style in naming the variables in ABAP. These naming convention might help you remember and differentiate variables that you used, but keep in mind that you might need to follow a different naming convention in every project.

Variable Type	Usage
Global Varibles	gv_<variablename>
	d_<variablename>
Local Variable	lv_<variablename>
	ld_<variablename>
Global Internal Table	it_<internaltablename>
	gt_<internaltablename>
Local Internal Table	lt_<internaltablename>
Global Work Area	gw_<workareaname>
Local Work Area	lw_<workareaname>
	wa_<workareaname>
Constant	c_<constantname>
Parameter	p_<parametername>
Select_option	s_<selectoptionname>
Ranges	r_<rangename>
Type Structure	ty_<structurename>
Subroutines	F_<subroutinename>
	FORM_<subroutinename>

Source: 

https://archive.sap.com/discussions/thread/531835 

SAP Basic Operators, Keywords, Functions

Arithmetic Operators

Operator	Using Operator	Using Keyword
Less than	a < b	a LT B
Greater than	a > b	a GT b
Less than or equal	a <= b	a LE b
Greater than or equal	a >= b	a GE b
Equal	a = b	a EQ b
Not equal	a <> b	a NE b

Comparison Operators

Operator	Using Operator	Using Keyword
Addition	p = n + m.	ADD n TO m.
Subtraction	P = m – n.	SUBTRACT n FROM m.
Multiplication	P = m * n.	MULTIPLY m BY n.
Division	P = m / n.	DIVIDE m BY n.
Integer division	P = m DIV n.	---
Remainder of division	P = m MOD n.	---
Powers	P = m ** n.	---

Logical Expressions

Expression	Usage
AND	(a<b) and (a<c)
OR	(a<b) or (a<c)
NOT	a NOT b
BETWEEN	a BETWEEN b AND c
IS	a IS (NULL/ASSIGNED/BOUND/INITIAL)

Numeric Data Types Functions

DATA

DATA n TYPE p DECIMALS 2.
DATA m TYPE p DECIMALS 2 VALUE '-5.55'.

Function		Usage				Output
ABS		n = abs( m ).  WRITE:  'ABS: ', n.				ABS: 5.55
SIGN		n = sign( m ). WRITE: / 'SIGN: ', n.				SIGN:  1.00-
CEIL		n = ceil( m ). WRITE: / 'CEIL: ', n.				CEIL:  5.00-
FLOOR		n = floor( m ). WRITE: / 'FLOOR:', n.				FLOOR: 6.00-
TRUNC		n = trunc( m ). WRITE: / 'TRUNC:', n.				TRUNC: 5.00-
FRAC		n = frac( m ). WRITE: / 'FRAC: ', n.				FRAC:  0.55-

Floating-Point Functions

Function	Meaning
acos, asin, atan; cos, sin, tan	Trigonometric functions.
cosh, sinh, tanh	Hyperbolic functions.
exp	Exponential function with base e (e=2.7182818285).
log	Natural logarithm with base e.
log10	Logarithm with base 10.
sqrt	Square root.

String Logical Expression

CO	str1 only contains characters from <str2>;
CN	str1 contains characters not only from str2 (corresponds to NOT str1 CO str2);
CA	str1 contains at least one character from str2;
NA	str1 does not contain any characters from str2;
CS	str1 contains the string str2;
NS	str1 does not contain the string str2;
CP	str1 contains the pattern str2;
NP	str1 does not contain the pattern str2;

String Functions

DATA: title(15) TYPE c VALUE 'Mr',

surname(40) TYPE c VALUE 'Smith',
Forename(40) TYPE c VALUE 'Joe',
sep,  "an empty character by default"
Destination(200) TYPE c,
spaced_name TYPE STRING VALUE 'Joe Smith',
len TYPE i.

Function	Usage	Output
CONCATENATE	DATA: title(15) TYPE c VALUE 'Mr',
	surname(40) TYPE c VALUE 'Smith',
	forename(40) TYPE c VALUE 'Joe',
	sep,  "an empty character by default"
	destination(200) TYPE c.
	CONCATENATE title surname forename INTO destination SEPARATED BY sep.	Mr Smith Joe
CONDENSE	DATA spaced_name TYPE string VALUE 'Joe         Smith'.
	CONDENSE spaced_name.	Joe Smith
CONDENSE NO GAPS	CONDENSE spaced_name NO-GAPS.	JoeSmith
STRLEN	DATA len TYPE i.
	len = strlen( surname ).
	WRITE / len.
	strlen( surname ).	5
REPLACE	REPLACE ' ' WITH '-' INTO destination.	Mr-Smith Joe
	REPLACE ' ' WITH '-' INTO destination.	Mr-Smith-Joe
REPLACE ALL OCCURRENCES	REPLACE ALL OCCURRENCES OF '-' IN destination WITH '+'.	Mr+Smith+Joe
SEARCH	destination = 'Mr. Smith Joe'.
	SEARCH destination for 'Joe   '.	sy-fdpos 10
	SEARCH destination for  '*ith'.	sy-fdpos 4
	SEARCH destination for 'John'.	sy-subrc 4
SHIFT	DATA empl_num TYPE STRING VALUE '0000654321'.
	SHIFT empl_num. "become 000654321	000654321
SHIFT DELETE LEADING	empl_num = '0000654321'.
	SHIFT empl_num left deleting leading '0'. "become 654321	654321
SHIFT CURCULAR	empl_num = '0000654321'.
	SHIFT empl_num CIRCULAR.	0006543210
SPLIT	DATA mystring TYPE string VALUE '1234** ACBD **6789'.
	DATA: a(10) TYPE c,
	b(10) TYPE c,
	c(10) TYPE C,	a 1234
	sep2(2) TYPE c VALUE '**'.	b  ABCD
	SPLIT mystring AT sep2 INTO a b c.	c 6789
SUBFIELDS	DATA: int_tel_num(17) TYPE c VALUE '+62-812345678',
	country_code(3) TYPE c,
	tel_num(14) TYPE c.
	country_code = int_tel_num(3).	62
	tel_num = int_tel_num+4(13).	812345678

Formatting String Functions

Function	Description
LEFT-JUSTIFIED	Specifies that the output is left-justified.
CENTERED	Denotes that the output is centered.
RIGHT-JUSTIFIED	Specifies that the output is right-justified.
UNDER <g>	The output starts directly under the field <g>.
NO-GAP	Specifies that the blank after field <f> is rejected.
USING EDIT MASK <m>	Denotes the specification of the format template <m>. Using No EDIT Mask: This specifies that the format template specified in the ABAP Dictionary is deactivated.
NO-ZERO	If a field contains only zeroes, then they are replaced by blanks.

Formatting Numeric Functions

Function	Description
NO-SIGN	Specifies that no leading sign is displayed on the screen.
EXPONENT <e>	Specifies that in type F (the floating point fields), the exponent is defined in <e>.
ROUND <r>	The type P fields (packed numeric data types) are first multiplied by 10**(-r) and then rounded off to an integer value.
CURRENCY <c>	Denotes that the formatting is done according to the currency <c> value that is stored in the TCURX database table.
UNIT <u>	Specifies that the number of decimal places is fixed according to the <u> unit as specified in the T006 database table for type P.
DECIMALS <d>	Specifies that the number of digits <d> must be displayed after the decimal point.

Main Source:
https://www.tutorialspoint.com/sap_abap

Hello World!

Hello World! This is the first post i just published on the day i made this blog on 31th January 2017. I believe most of the readers here have been familiar with my "Hello World!" phrase which is used in your very first program with a particular new language and here I will share my knowledge in ABAP language in this blog for everyone to learn.

If you haven't heard of ABAP, it is stands for Advanced Business Application Programming, originally Allgemeiner Berichts-Aufbereitungs-Prozessor in German, a high-level programming language created by the German software company, SAP SE. Hence, it can only be used in its ERP Software's environment, SAP for customisations of feature implementation in it.

By the way, my name is Evan Christiawan, I am a graduate student from Murdoch University majoring in Computer Science and Cyber Forensics. Currently, I work as ABAP technical consultant at Soltius Indonesia, a subsidiary of Metrodata Group that focuses its business in dealing with SAP Solution to help companies run better.

I think that's all for the introduction and won't introduce more about me unless you want to know me more :). Hopefully i can keep updating posts/notes in this blog and help lots of people who are curious in learning ABAP, a language of SAP.