RTL/2

<h2 id="language-overview">Language overview</h2>
<p>The <a href="/facts/Data_type/fcx5hgVL">data types</a> in RTL/2 were <a href="/facts/Strong_and_weak_typing/WYexudnr">strongly typed</a>, with separate <a href="/facts/Compiler/WNfCDFJe">compiling</a>. The <a href="/facts/Translation_unit_(programming)/7GbSbEYL">compilation units</a> contained one or more items named <i>bricks</i>, i.e.:
</p>
<ul><li>Procedure bricks</li>
<li>Data bricks</li>
<li>Stack bricks</li></ul>
<p>A procedure brick was a <a href="/facts/Subroutine/9vFJrg0A">procedure</a>, which may or may not return a (scalar) value, have (scalar) parameters, or have local (scalar) <a href="/facts/Variable_(computer_science)/VoCKtwml">variables</a>. The entry mechanism and implementation of <a href="/facts/Local_variable/q8sIjyhx">local variables</a> was <a href="/facts/Reentrancy_(computing)/VMYdeEvw">reentrant</a>. Non-scalar data could only be accessed via reference (so-called REF variables were considered scalar).
</p><p>A data brick was a named static collection of scalars, arrays and records. There was no heap or <a href="/facts/Garbage_collection_(computer_science)/j2vlIu7g">garbage collection</a>, so programmers had to implement <a href="/facts/Memory_management/vthLkUpz">memory management</a> manually.
</p><p>A <a href="/facts/Stack_(abstract_data_type)/bj7l94v1">stack</a> brick was an area of storage reserved for running all the procedures of a single process and contained the call stack, local variables and other housekeeping items. The extent to which stack bricks were used varied depending on the host environment in which RTL/2 programs ran.
</p><p>Access to the host environment of an RTL/2 program was provided via special procedure and data bricks called <i>SVC procedures</i> and <i>SVC data</i>. These were accessible in RTL/2 but implemented in some other language in the host environment.
</p>
<h2 id="hello-world">Hello World</h2>
TITLE Hello World;

LET NL=10;

EXT PROC(REF ARRAY BYTE) TWRT;

ENT PROC RRJOB() INT;
TWRT("Hello World#NL#");
RETURN(1);
ENDPROC;

<h2 id="embedded-assembly">Embedded assembly</h2>
<p>RTL/2 compiles to <a href="/facts/Assembly_language/7XuV0cla">assembly language</a> and provides the CODE statement to allow including assembly language in RTL/2 <a href="/facts/Source_code/o9J6Jv23">source code</a>. This is only available when compiled with a <a href="/facts/Systems_programming/urTteIsW">systems programming</a> option (CN:F)
</p><p>The CODE statement takes two operands: the number of bytes used by the code insert and the number of bytes of stack used.
</p><p>Within code statements two trip characters are used to access RTL/2 variables. These vary between different <a href="/facts/Operating_system/8XTuvMh2">operating systems</a>. On a <a href="/facts/Digital_Equipment_Corporation/ztxs6keA">Digital Equipment Corporation</a> (DEC) <a href="/facts/PDP-11/9HkGUzFn">PDP-11</a> running RSX-11M, and a <a href="/facts/VAX/N3r13IHH">VAX</a> running <a href="/facts/OpenVMS/rAnHAgpD">VMS</a>, the trip characters are * and /.
</p><p>While the specifics varied by operating system the following is an example of a code insert on VAX/VMS:
</p>
CODE 6,0;
JMP CODE_ENT ; This code insert can be set to a fixed length as it jumps to a new psect.
; this method is especially useful on systems such as VMS where the length of
; instructions is variable
.SAVE_PSECT ; Save current program section
.PSECT ASMB_CODE,EXE,NOWRT,LONG
CODE_ENT:
MOVL *PARAM1(AP),*COUNTER/MYDATA
JMP CODE_EX
.RESTORE_PSECT
CODE_EX:
*RTL

<p>This code insert moves the value of a variable passed into the RTL/2 procedure into a variable named COUNTER in a data brick named MYDATA.
</p>
<h2 id="reserved-words">Reserved words</h2>

<ul><li>ABS</li>
<li>AND</li>
<li>ARRAY</li>
<li>BIN</li>
<li>BLOCK</li>
<li>BY</li>
<li>BYTE</li>
<li>CODE</li>
<li>DATA</li>
<li>DO</li>
<li>ELSE</li>
<li>ELSEIF</li>
<li>END</li>
<li>ENDBLOCK</li>
<li>ENDDATA</li>
<li>ENDPROC</li>
<li>ENT</li>
<li>EXT</li>
<li>FOR</li>
<li>FRAC</li>
<li>GOTO</li>
<li>HEX</li>
<li>IF</li>
<li>INT</li>
<li>LABEL</li>
<li>LAND</li>
<li>LENGTH</li>
<li>LET</li>
<li>LOR</li>
<li>MOD</li>
<li>NEV</li>
<li>NOT</li>
<li>OCT</li>
<li>OF</li>
<li>OPTION</li>
<li>OR</li>
<li>PROC</li>
<li>REAL</li>
<li>REF</li>
<li>REP</li>
<li>RETURN</li>
<li>RTL</li>
<li>SHA</li>
<li>SHL</li>
<li>SLA</li>
<li>SLL</li>
<li>SRA</li>
<li>SRL</li>
<li>STACK</li>
<li>SVC</li>
<li>SWITCH</li>
<li>THEN</li>
<li>TITLE</li>
<li>TO</li>
<li>VAL</li>
<li>WHILE</li></ul>

<h3>SPL documentation</h3>
<p>SPL published a range of documentation for RTL/2. Each such document was assigned a reference number. The following is an incomplete list.
</p>
RTL/2 Ref 1  – RTL/2 Language Specification
RTL/2 Ref 2  – Introduction to RTL/2
RTL/2 Ref 3  – RTL/2 Training Manual
RTL/2 Ref 4  – System Standards
RTL/2 Ref 5  – Stream I/O
RTL/2 Ref 18 – Hints on writing RTL/2 Programs
RTL/2 Ref 26 – Language Reference Card
RTL/2 Ref 39 – Run time environment on the PDP-11
RTL/2 Ref 63 – User Manual for the PDP-11 under RSX-11M
RTL/2 Ref 107 – VAX/VMS RTL/2 User Manual
RTL/2 REF 130 – The RTL/2 32-bit run time environment on the VAX

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Barnes, J.G.P. (September 1980). "The Standardisation of RTL/2". Software: Practice and Experience. 10 (9). Wyley: 707–719. doi:10.1002/spe.4380100904. S2CID 5050804. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>RTL/2 Language Specification <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>"The Encyclopedia of Computer Languages". Archived from the original on 10 March 2011. <a href="https://web.archive.org/web/20110310112048/http://hopl.murdoch.edu.au/showlanguage2.prx?exp=596" target="_blank">https://web.archive.org/web/20110310112048/http://hopl.murdoch.edu.au/showlanguage2.prx?exp=596</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Barnes, J.G.P. (1 January 1976). RTL/2 design and philosophy. Heyden. ISBN 978-0855012243. <a href="978-0855012243" target="_blank">978-0855012243</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>BS 5904:1980: Specification for computer programming language RTL/2. 30 September 1980. ISBN 978-0580114410. {{cite book}}: |website= ignored (help) <a href="978-0580114410" target="_blank">978-0580114410</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
</ol>

RTL/2 open-in-new

RTL/2