BLISS is a
system programming language
A system programming language is a programming language used for system programming; such languages are designed for writing system software, which usually requires different development approaches when compared with application software. Edsger W ...
developed at
Carnegie Mellon University (CMU) by
W. A. Wulf, D. B. Russell, and
A. N. Habermann around 1970. It was perhaps the best known system language until
C debuted a few years later. Since then, C became popular and common, and BLISS faded into obscurity. When C was in its infancy, a few projects within
Bell Labs
Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984),
then AT&T Bell Laboratories (1984–1996)
and Bell Labs Innovations (1996–2007),
is an American industrial Research and development, research and scientific developm ...
debated the merits of BLISS vs. C.
BLISS is a
typeless block
Block or blocked may refer to:
Arts, entertainment and media Broadcasting
* Block programming, the result of a programming strategy in broadcasting
* W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 ...
-
structured programming language based on expressions rather than statements, and includes constructs for
exception handling
In computing and computer programming, exception handling is the process of responding to the occurrence of ''exceptions'' – anomalous or exceptional conditions requiring special processing – during the execution of a program. In general, an ...
,
coroutine
Coroutines are computer program components that generalize subroutines for non-preemptive multitasking, by allowing execution to be suspended and resumed. Coroutines are well-suited for implementing familiar program components such as cooperative ...
s, and
macros. It does not include a
goto statement.
The name is variously said to be short for ''Basic Language for Implementation of System Software'' or ''System Software Implementation Language, Backwards''. It was sometimes called "Bill's Language for Implementing System Software", after Bill Wulf.
The original Carnegie Mellon
compiler
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs tha ...
was notable for its extensive use of
optimizations, and formed the basis of the classic book ''
The Design of an Optimizing Compiler
''The Design of an Optimizing Compiler'' (Elsevier Science Ltd, 1980, ), by William Wulf, Richard K. Johnson, Charles B. Weinstock, Steven O. Hobbs, and Charles M. Geschke, was published in 1975 by Elsevier. It describes the BLISS optimizing comp ...
''.
Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president un ...
(DEC) developed and maintained BLISS compilers for the
PDP-10
Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, espec ...
,
PDP-11,
VAX
VAX (an acronym for Virtual Address eXtension) is a series of computers featuring a 32-bit instruction set architecture (ISA) and virtual memory that was developed and sold by Digital Equipment Corporation (DEC) in the late 20th century. The V ...
,
DEC PRISM
PRISM (Parallel Reduced Instruction Set Machine) was a 32-bit RISC instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). It was the outcome of a number of DEC research projects from the 1982–1985 time-frame, and t ...
,
MIPS,
DEC Alpha
Alpha (original name Alpha AXP) is a 64-bit reduced instruction set computer (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). Alpha was designed to replace 32-bit VAX complex instruction set compute ...
,
and Intel
IA-32
IA-32 (short for "Intel Architecture, 32-bit", commonly called i386) is the 32-bit version of the x86 instruction set architecture, designed by Intel and first implemented in the 80386 microprocessor in 1985. IA-32 is the first incarnation o ...
,
The language did not become popular among customers and few had the compiler,
but DEC used it heavily in-house into the 1980s; most of the utility programs for the
OpenVMS operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
were written in BLISS-32. The DEC BLISS compiler has been ported to the
IA-64
IA-64 (Intel Itanium architecture) is the instruction set architecture (ISA) of the Itanium family of 64-bit Intel microprocessors. The basic ISA specification originated at Hewlett-Packard (HP), and was subsequently implemented by Intel in col ...
and
x86-64
x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging ...
architectures as part of the ports of OpenVMS to these platforms.
The x86-64 BLISS compiler uses
LLVM
LLVM is a set of compiler and toolchain technologies that can be used to develop a front end for any programming language and a back end for any instruction set architecture. LLVM is designed around a language-independent intermediate repre ...
as its backend
code generator In computing, Code generation denotes software techniques or systems that generate program code which may then be used independently of the generator system in a runtime environment.
Specific articles:
* Code generation (compiler), a mechanism to pr ...
, replacing the proprietary GEM backend used for Alpha and IA-64.
Language description
The BLISS language has the following characteristics:
* All ''constants'' are full word for the machine being used, e.g. on a 16-bit machine such as the
PDP-11, a constant is 16 bits; on a
VAX
VAX (an acronym for Virtual Address eXtension) is a series of computers featuring a 32-bit instruction set architecture (ISA) and virtual memory that was developed and sold by Digital Equipment Corporation (DEC) in the late 20th century. The V ...
computer, constants are 32 bits, and on a
PDP-10
Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, espec ...
, a constant is 36 bits.
* 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.
* ''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
) places the constant 14 into the location which is 12 words after the address of Z. (This is considered bad practice.)
* ''Block statements'' are similar to those of
ALGOL
ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the ...
: a block is started with a
BEGIN
statement and terminated with
END
. As with ALGOL, statements are terminated 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
precedence rules are used, in which parenthesized expressions are computed first,
* ''Conditional execution'' uses the
IF
expression, which tests a true-false condition, performs alternative actions, and returns a result.
* ''Comparison'' uses keywords such as
EQL
for equality (as opposed to
overloading 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:
::
Q = (IF .Z GTR 0 THEN .Z ELSE -.Z);
* ''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.
* ''
Subroutines'' in the language are called ''routines'', and are declared with the keyword
ROUTINE
.
* ''Macros'', which allow for text substitution, are declared with the keyword
MACRO
.
* The language supports ''
arrays
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
{{TOC right
Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
'', which are referred to as ''structures'', and declared with the keyword
VECTOR
.
* The language supports some ''
high-level programming language
In computer science, a high-level programming language is a programming language with strong abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language ''elements'', be easier to us ...
constructs'' such as:
**''Alternative execution paths'' via the
CASE
expression
**''Looping'' through use of the
INCR
expression, which is similar to ALGOL's FOR statement
**Built-in ''
string functions''
**Certain automatic ''data conversions'' (number to string, etc.)
Source example
The following example is taken verbatim from the ''Bliss Language Manual'':
[
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
]
Versions
* BLISS-10
* BLISS-11 - a cross compiler
A cross compiler is a compiler capable of creating executable code for a platform other than the one on which the compiler is running. For example, a compiler that runs on a PC but generates code that runs on an Android smartphone is a cross c ...
for the PDP-11
* BLISS-16
* BLISS-16C - DEC version of BLISS-11
* BLISS-32
* BLISS-36
* BLISS-64
* Common BLISS - portable subset
Notes
References
* Also
"BLISS: A Language for Systems Programming"
(PostScript)
* Wulf, W. A.; Johnson, R. K.; Weinstock, C. B.; Hobbs, S. O.; Geschke, C. M. (1975). ''The Design of an Optimizing Compiler
''The Design of an Optimizing Compiler'' (Elsevier Science Ltd, 1980, ), by William Wulf, Richard K. Johnson, Charles B. Weinstock, Steven O. Hobbs, and Charles M. Geschke, was published in 1975 by Elsevier. It describes the BLISS optimizing comp ...
''. New York: Elsevier, .
*
External links
BLISS Manual at DECUS
* Lehotsky, Alan
a post about BLISS at DEC
* Madison, Matthew D.
Session notes for "Introduction to BLISS"
(PostScript)
Downloads
BLISS-10
* tp://ftp.iecc.com/pub/file/bliss.tar.gz BLISS-11
BLISS-36
BLISS-11, BLISS-32 and BLISS-64
* tp://freevms.nvg.org/pub/vms/freevms/ FreeVMS Portable BLISS for GCC
{{Carnegie Mellon
Systems programming languages
OpenVMS software
Carnegie Mellon University software
Programming languages
Programming languages created in 1970