• Human-centered language (simple syntax)
  • easy syntax and therefore quick to learn
• Powerful object-model
  • All important concepts of the object-oriented paradigm available
• Scripting language
  • Automation ("remote controlling") of applications and operating systems like Linux (D-Bus) or Windows (Windows Scripting Engine)
• BSF4ooRexx (Java-Bridge)
  • All of Java immediately available camouflaged as ooRexx
• Easy entry into other programming languages (e.g.: Java, Python)

• Course materials
  • Slides: http://wi.wu.ac.at/rgf/wu/lehre/autowin/material/foils
• Related seminar, diploma, bachelor and master theses
  • https://wi.wu.ac.at/rgf/diplomarbeiten/
• Book
  • Flatscher R.G.: "Introduction to Rexx and ooRexx – From Rexx to Open Object Rexx (ooRexx)", facultas Management Book Service
• Browser based ooRexx workbench with numerous examples and debugging abilities by Josep Maria Blasco
  • ooRexx Playground: https://rexx.epbcn.com/oorexx-wasm/
• More goodies from Josep Maria Blasco
  • Josep Maria's GitHub: https://github.com/JosepMariaBlasco

• Rexx Language Association (non-profit SIG): https://www.RexxLA.org
• Latest ooRexx (beta versions are usually stable, fully productive)
  • Installation packages (needs administration rights)
    • https://sourceforge.net/projects/oorexx/files/oorexx/
  • Considerations:
    • Operating System: Linux, MacOS or Windows
    • Bitness: 32bit (Linux, Windows) or 64bit (Linux, MacOS, Windows)
    • Architecture: x86, ARM, Apple M1, ...
• Resources at WU:
  • Virtual PC labs: https://labconnect.wu.ac.at/
  • FAQ: https://learn.wu.ac.at/open/distanzlehre/de/virtuellpc

• 1979 – Mike F. Cowlishaw (IBM-Fellow)
  • REXX: Acronym for "REstructured eXtended eXecutor"
  • Human-centric successor of “EXEC” language on IBM mainframes
  • Interactive (interpreter)
  • Keywords are English, resulting code looks like pseudo-code!
  • No reserved keywords unlike many other programming languages!
• 1987 – IBM’s System Application Architecture (SAA)
  • Procedural script language for all IBM platforms
  • Commercial and open source versions available for all operating systems
• 1996 – ANSI/INCITS "Programming Language – REXX" (INCITS 274:1996[S2008])

• Since 1990s – Development of an object-oriented REXX
  • Fully compatible with classic ("procedural") REXX but still with a simple syntax
  • Internally fully object-oriented (classic REXX statements are transformed)
  • Powerful object model (e.g. meta-classes, multiple inheritance)
• 1996 – Mike F. Cowlishaw development of NetREXX
  • NetRexx-programs are translated into Java byte code
  • Simpler programming of the Java VM (~30% less Code)
  • IBM handed over source code to RexxLA (http://www.RexxLA.org/)
    • June, 8th, 2011 opensource released by RexxLA

• May 2004 – Negotiations about open-sourcing Object Rexx
  • IBM: Manfred Schweizer, manager of IBM's REXX development team
  • RexxLA: Pam Taylor (experienced commercial manager, USA), Mark Hessling (maintainer of Regina and author of numerous Rexx libraries, Australia), Rony G. Flatscher (MIS professor, Austria/Europe)
• October 2004 – Object REXX → "Open Object REXX" (ooRexx)
• April 2005 – RexxLA releases the opensource version of ooRexx
• ooRexx 5.2.0 released in May 2026
  • BSF4ooRexx850 a bridge between ooRexx and Java is available
  • ooRexx 5.2.0 released, work on ooRexx 5.3.0 has started
  • Work on bridges from ooRexx to .NET, Python, Lua, and JavaScript started

• The Hello World program is a tradition that dates back to 1974.

  /* a comment */
  SAY "Hello, my beloved world"

  Output:

  Hello, my beloved world

• Upper or lowercase spelling irrelevant
  • All characters of a statement will be translated into uppercase and executed
• Exception: Contents of a string remains unchanged

  • Strings are delimited by apostrophes (') or by quotes (")

    "Richard", 'Richard', "\{[]}\gulp!öäüß!{niX }"

• Multiple blank characters between symbols are reduced to one blank, removed around operators

  • Example:

    saY    "\{[]}\gulp!öäüß!{niX }"   reverse(  Abc )

  • Becomes:

    SAY "\{[]}\gulp!öäüß!{niX }" REVERSE(ABC)

• Characters outside of strings and comments must be from the following character set
  • Blank
  • a thru z
  • A thru Z
  • 0 thru 9
  • Exclamation mark (!), backslash (\), question mark (?), equal sign (=), comma (,), minus (-), plus (+), dot (.), Slash (/), parentheses (()), square brackets ([]), asterisk (*), tilde (~), semicolon (;), colon (:) and underscore (_)

• Variables allow storing, changing, and retrieving strings with the help of a discretionary name called an identifier

  A = "Hello, my beloved world"
  a="Hello, my beloved variable"
  A        =       a        "- changed again."
  say a

  Output:

  Hello, my beloved variable - changed again.

• Identifiers must begin with a letter, an exclamation mark, a question mark or an underline character, followed by one or more of these characters, digits, and dots.

• Constants never get their values changed
• It is possible to use literals which are string constants appearing verbatim in an expression
  • If one wishes to name constants, then there are a few possibilities available, e.g.

    1. The constant value is assigned to a variable, the value of which never gets changed in the entire program (after all, it is a constant!)

       Pi = 3.14159

    2. In ooRexx use the ::constant name value directive

• Comments may be nested and are allowed to span multiple lines.

  say 3    +   /* This /**/ is
        a /* nested
             /* aha */ comment */ which spans
           multiple lines */ 4

  Output:

  7

• Line comments: at the end of a statement, comments follow after two consecutive dashes:

  say 3 + 4 -- this yields "7"

  Output:

  7

• Statements consist of all characters up to and including the semi-colon (;)

• There may an arbitrary number of statements on a line

• If the semi-colon is missing, then the end of a statement is assumed by the end of a line

  /* Some comment */
  SAY "Hello, my dear world";

  Output:

  Hello, my dear world

• Statements may span multiple lines, but you need to indicate this with the continuation character
  • A dash (-) or comma (,) as the very last character on the line

• A block is a statement, which may comprise an arbitrary number of statements
• A block starts with the keyword DO and ends with END

• Two values (constant, variable, results of function calls) can be compared with the following (Infix) operators (Result: 0=false or 1=true)

  =	equal
  <> \=	unequal
  <	smaller
  <=	smaller than
  >	greater
  >=	greater than

• Negation of Boolean (0=false, 1=true) values

  \

  Negator

• Boolean values can be combined

  &	"and" (true: if both arguments are true)
  |	"or" (true: if either argument is true)
  &&	"exclusive or" (true: if one argument is true and the other is false)

• Boolean combinations can be evaluated in a specific order if enclosed in parentheses:

  0 & 1 | 1	Result: 1 (= true)
  (0 & 1) | 1	Result: 1 (= true)
  0 & (1 | 1)	Result: 0 (= false)

• A branch determines which statement (block) should be executed as a result of a comparison (of a Boolean value)

  • IF test_expression=.true THEN statement;

    IF age < 19 THEN SAY "Young."

• A branch can also determine what alternative statement (block) should be executed, in case the Boolean value is false

  • IF test_expression=.true THEN statement; ELSE statement;

    IF age < 19 THEN SAY "Young."
                 ELSE SAY "Old."

    IF age < 1 THEN
    DO
         SAY "Hello,"
         SAY "my beloved world"
    END

• Multiple selections (SELECT)

  SELECT
     WHEN test_expression THEN statement;
     WHEN test_expression THEN statement;
        /* ... additional WHEN-statements */
     OTHERWISE statement;
  END

  Example:

  SELECT
     WHEN age = 1   THEN SAY "Baby." ;
     WHEN age = 6   THEN SAY "Elementary school kid." ;
     WHEN age >= 10 THEN SAY "Big kid." ;
     OTHERWISE SAY "Unimportant." ;
  END

• A block can be executed repeatedly

  DO 3
       SAY "Aua!"
       SAY "Oh!"
  END

  Output:

  Aua!
  Oh!
  Aua!
  Oh!
  Aua!
  Oh!

• Using a variable to control the number of repetitions

  a = 3
  ...
  DO a
       SAY "Aua!"; SAY "Oh!"
  END

  Output:

  Aua!
  Oh!
  Aua!
  Oh!
  Aua!
  Oh!

• Repetition using a loop variable ("i" in this example)

  DO i = 1 TO 3
       SAY "Aua!"; SAY "Oh!" i
  END

  Output:

  Aua!
  Oh! 1
  Aua!
  Oh! 2
  Aua!
  Oh! 3

• Repetition using a loop variable ("i" in this example)

  DO i = 1 TO 3 BY 2
       SAY "Aua!"; SAY "Oh!" i
  END

  Output:

  Aua!
  Oh! 1
  Aua!
  Oh! 3

• Repetition using a control variable ("i" in this example)

  DO i = 3.1 TO 5.7 BY 2.1
       SAY "Aua!"; SAY "Oh!" i
  END

  Output:

  Aua!
  Oh! 3.1
  Aua!
  Oh! 5.2

• Conditional repetition (evaluated at the beginning of the block)

  i = 2
  DO WHILE i < 3
       SAY "Aua!";SAY "Oh!" i
       i = i + 1
  END

  Output:

  Aua!
  Oh! 2

• Conditional repetition (evaluated at the beginning of the block)

  i = 3
  DO WHILE i < 3
       SAY "Aua!";SAY "Oh!" i
       i = i + 1
  END

  Output:

→ No output, because block is not executed!

• Exit condition (evaluated at the end of the block)

  i = 3
  DO UNTIL i > 1
       SAY "Aua!";SAY "Oh!" i
       i = i + 1
  END

  Output:

  Aua!
  Oh! 3