BLISS

<h2 id="language-description">Language description</h2>
[excessive quote]

<blockquote>BLISS has many of the features of other modern high-level languages. It has block structure, an automatic stack, and mechanisms for defining and calling recursive routines ... provides a variety of predefined data structures and ... facilities for testing and iteration ...
On the other hand, BLISS omits certain features of other high-level languages. It does not have built-in facilities for input/output, because a system-software project usually develops its own input/output or builds on basic monitor I/O or screen management services ... it permits access to machine-specific features, because system software often requires this. BLISS has characteristics that are unusual among high-level languages. A name ... is uniformly interpreted as the address of that segment rather than the value of the segment ... Also, BLISS is an "expression language" rather than a "statement language".

This means that every construct of the language that is not a declaration is an expression. Expressions produce a value as well as possibly causing an action such as modification of storage, transfer of control, or execution of a program loop. For example, the counterpart of an assignment "statement" in BLISS is, strictly speaking, an expression that itself has a value. The value of an expression can be either used or discarded in BLISS ... Finally, BLISS includes a macro facility that provides a level of capability usually found only in macro-assemblers.— Bliss Language Manual, <a href="/facts/Digital_Equipment_Corporation/ztxs6keA">Digital Equipment Corporation</a> (1987)<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a></blockquote>
The BLISS language has the following characteristics:

<ul><li>All constants are full word for the machine being used, e.g. on a 16-bit machine such as the <a href="/facts/PDP-11/9HkGUzFn">PDP-11</a>, a constant is 16 bits; on a <a href="/facts/VAX/N3r13IHH">VAX</a> computer, constants are 32 bits, and on a <a href="/facts/PDP-10/zlfam4wk">PDP-10</a>, a constant is 36 bits.</li>
<li>A reference to a variable is always to the address of that variable. For example, the instruction Z+8 refers to adding 8 to the address of Z, not to its value. If one needs to add 8 to the value of Z, one must prefix the variable with a period; so one would type .Z+8 to perform this function, which adds 8 to the contents of Z.</li>
<li>Assignment is done with the standard = symbol, e.g. Z=8 – which says to create a full-word constant containing 8, and store it in the location whose address corresponds to that of Z. So Z+12=14 (or, alternatively 12+Z=14 though this form is considered bad practice per the BLISS documentation in Digital) places the constant 14 into the location which is 12 words after the address of Z.</li>
<li>Block statements are similar to those of <a href="/facts/ALGOL/wlFJGNEx">ALGOL</a>: a block is started with a BEGIN statement and terminated with END. As with ALGOL, statements are separated with the semicolon (";"). When a value is computed, it is saved until the next statement terminator – which means that a value can be computed, assigned to a variable, and carried forward to the next statement, if desired. Alternatively, an open parenthesis may be used to begin a block, with the close parenthesis used to close the block. When parentheses are included in an expression, the standard <a href="/facts/Order_of_operations/sWsoTzbH">precedence</a> rules are used, in which parenthesized expressions are computed first,</li>
<li>Conditional execution uses the IF expression, which tests a true-false condition, performs alternative actions, and returns a result.</li>
<li>Comparison uses keywords such as EQL for equality (as opposed to <a href="/facts/Operator_overloading/hRyHs4Qf">overloading</a> the = symbol for the same purpose), GTR for Greater Than, and NEQ for not equal. For example, the following code will assign the absolute value of Z to the address indicated by Q:</li></ul>
Q = (IF .Z GTR 0 THEN .Z ELSE -.Z);
<ul><li>Identifiers (variables and constants) must be declared before use, typically using the OWN keyword. Declaring a variable normally causes the compiler to allocate space for it; when necessary, a variable may be assigned a fixed machine address via the BIND declaration. This feature is primarily used for accessing either machine registers or certain special addresses.</li>
<li><a href="/facts/Subroutine/9vFJrg0A">Subroutines</a> in the language are called routines, and are declared with the keyword ROUTINE.</li>
<li>Macros, which allow for text substitution, are declared with the keyword MACRO.</li>
<li>The language supports <a href="/facts/Array_data_structure/BKGvF8AM">arrays</a>, which are referred to as structures, and declared with the keyword VECTOR.</li>
<li>The language supports some <a href="/facts/High-level_programming_language/smjECUhx">high-level programming language</a> constructs such as:
<ul><li>Alternative execution paths via the CASE expression</li>
<li>Looping through use of the INCR expression, which is similar to ALGOL's FOR statement</li>
<li>Built-in <a href="/facts/String_(computer_science)/4ChJu5WS">string</a> functions</li>
<li>Certain automatic data conversions (number to string, etc.)</li></ul></li></ul>
<h2 id="source-example">Source example</h2>
The following example is taken verbatim from the Bliss Language Manual:<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a>

MODULE E1 (MAIN = CTRL) =
BEGIN
FORWARD ROUTINE
 CTRL,
 STEP;
ROUTINE CTRL =
!+
! This routine inputs a value, operates on it, and
! then outputs the result.
!-
 BEGIN
 EXTERNAL ROUTINE
 GETNUM,  ! Input a number from terminal
 PUTNUM;  ! Output a number to terminal
 LOCAL
 X,  ! Storage for input value
 Y;  ! Storage for output value
 GETNUM(X);
 Y = STEP(.X);
 PUTNUM(.Y)
 END;
ROUTINE STEP(A) =
!+
! This routine adds 1 to the given value.
!-
 (.A+1);
END
ELUDOM

<h2 id="versions">Versions</h2>
<ul><li>BLISS-10</li>
<li>BLISS-11 - a <a href="/facts/Cross_compiler/8hXgCWB9">cross compiler</a> for the PDP-11</li>
<li>BLISS-16</li>
<li>BLISS-16C - DEC version of BLISS-11</li>
<li>BLISS-32</li>
<li>BLISS-36</li>
<li>BLISS-64</li>
<li>Common BLISS - portable subset</li></ul>
<h2 id="notes">Notes</h2>

<ul><li><a href="/facts/William_Wulf/25eh9Btm">Wulf, W. A.</a>; Russell, D. B.; <a href="/facts/Nico_Habermann/2h7DpL6S">Habermann, A. N.</a> (December 1971). <a href="http://www.cs.arizona.edu/classes/cs520/spring06/bliss.pdf">"BLISS: A Language for Systems Programming"</a> (PDF). <a href="/facts/Communications_of_the_ACM/Ix1DvEAk">Communications of the ACM</a>. 14 (12): 780–790. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1145%2F362919.362936">10.1145/362919.362936</a>. <a href="/facts/S2CID_(identifier)/ldJsHa2Y">S2CID</a> <a href="https://api.semanticscholar.org/CorpusID:9564255">9564255</a>. Also: <a href="http://vms.process.com/scripts/fileserv/fileserv.com?BLISS-ARTICLE">"BLISS: A Language for Systems Programming"</a>. (PostScript)</li>
<li>Wulf, W. A.; Johnson, R. K.; Weinstock, C. B.; Hobbs, S. O.; Geschke, C. M. (1975). <a href="/facts/The_Design_of_an_Optimizing_Compiler/YxI8YyWH">The Design of an Optimizing Compiler</a>. New York: Elsevier, <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 0-444-00158-1.</li>
<li>Brender, Ronald F. (2002). <a href="https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf">"The BLISS programming language: a history"</a> (PDF). Software: Practice and Experience. 32 (10): 955–981. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1002%2Fspe.470">10.1002/spe.470</a>. <a href="/facts/S2CID_(identifier)/ldJsHa2Y">S2CID</a> <a href="https://api.semanticscholar.org/CorpusID:45466625">45466625</a>.</li></ul>
<h2 id="external-links">External links</h2>
<ul><li><a href="https://web.archive.org/web/20061207101653/http://decus.decus.de:8080/htbin/webbook/PUBLIC$ROOT%3a%5bUTIL.BLISS%5d4358pro.p7.#1">BLISS Manual at DECUS</a></li>
<li>Lehotsky, Alan; <a href="http://compilers.iecc.com/comparch/article/87-07-029">a post about BLISS at DEC</a></li>
<li>Madison, Matthew D.; <a href="http://vms.process.com/scripts/fileserv/fileserv.com?BLISS-INTRO">Session notes for "Introduction to BLISS"</a> (PostScript)</li></ul>
<h3>Downloads</h3>
<ul><li><a href="http://pdp-10.trailing-edge.com/bb-m836d-bm/">BLISS-10</a></li>
<li><a href="ftp://ftp.iecc.com/pub/file/bliss.tar.gz">BLISS-11</a></li>
<li><a href="http://pdp-10.trailing-edge.com/bls36v42/">BLISS-36</a></li>
<li><a href="https://www.digiater.nl/openvms/freeware/v70/bliss/">BLISS-11, BLISS-32 and BLISS-64</a></li>
<li><a href="ftp://freevms.nvg.org/pub/vms/freevms/">FreeVMS Portable BLISS for GCC</a></li></ul>

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

<ol>
<li id="fn:1">Wulf, William A. (June 23, 2015). "An Interview with WILLIAM A. WULF OH 477" (PDF) (Interview). Interviewed by Jeffrey R. Yost. Charlottesville, Virginia. <a href="/wiki/William_Wulf" target="_blank">/wiki/William_Wulf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Brender, Ronald F. (2002). "The BLISS programming language: a history" (PDF). Software: Practice and Experience. 32 (10): 955–981. doi:10.1002/spe.470. S2CID 45466625. <a href="https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf" target="_blank">https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Brender, Ronald F. (2002). "The BLISS programming language: a history" (PDF). Software: Practice and Experience. 32 (10): 955–981. doi:10.1002/spe.470. S2CID 45466625. <a href="https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf" target="_blank">https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Brender, Ronald F. (2002). "The BLISS programming language: a history" (PDF). Software: Practice and Experience. 32 (10): 955–981. doi:10.1002/spe.470. S2CID 45466625. <a href="https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf" target="_blank">https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">MacLaren, Don (August 27, 1987). "DECWest Compiler Project, Description, and Plan" (PDF). Bitsavers.org. <a href="http://bitsavers.org/pdf/dec/prism/mica/870827_DECwest_Compiler_Project.pdf" target="_blank">http://bitsavers.org/pdf/dec/prism/mica/870827_DECwest_Compiler_Project.pdf</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Brender, Ronald F. (2002). "The BLISS programming language: a history" (PDF). Software: Practice and Experience. 32 (10): 955–981. doi:10.1002/spe.470. S2CID 45466625. <a href="https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf" target="_blank">https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Brender, Ronald F. (2002). "The BLISS programming language: a history" (PDF). Software: Practice and Experience. 32 (10): 955–981. doi:10.1002/spe.470. S2CID 45466625. <a href="https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf" target="_blank">https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Brender, Ronald F. (2002). "The BLISS programming language: a history" (PDF). Software: Practice and Experience. 32 (10): 955–981. doi:10.1002/spe.470. S2CID 45466625. <a href="https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf" target="_blank">https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">da Cruz, Frank (16 September 1987). "News about Kermit Programs for VAX/VMS". Info-Kermit Digest (Mailing list). Kermit Project, Columbia University. Retrieved 5 May 2019. Kermit-32 is written in the Bliss language, DEC's "corporate implementation language" (originally developed at CMU). Bliss never gained popularity among DEC's customers; few sites have Bliss compilers. <a href="http://www.columbia.edu/kermit/ftp/e/mail.87a" target="_blank">http://www.columbia.edu/kermit/ftp/e/mail.87a</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Brender, Ronald F. (2002). "The BLISS programming language: a history" (PDF). Software: Practice and Experience. 32 (10): 955–981. doi:10.1002/spe.470. S2CID 45466625. <a href="https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf" target="_blank">https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">"2017 LLVM Developers' Meeting: J. Reagan "Porting OpenVMS using LLVM"". YouTube. 31 October 2017. Archived from the original on 2021-12-21. <a href="https://www.youtube.com/watch?v=xTaBkCBYskA" target="_blank">https://www.youtube.com/watch?v=xTaBkCBYskA</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Bliss Language Manual, Digital Equipment Corporation (1987) <a href="http://www.digiater.nl/openvms/freeware/v80/bliss/documentation/blslref.pdf" target="_blank">http://www.digiater.nl/openvms/freeware/v80/bliss/documentation/blslref.pdf</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Bliss Language Manual, Digital Equipment Corporation (1987) <a href="http://www.digiater.nl/openvms/freeware/v80/bliss/documentation/blslref.pdf" target="_blank">http://www.digiater.nl/openvms/freeware/v80/bliss/documentation/blslref.pdf</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
</ol>

BLISS open-in-new

BLISS