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List of Names
- Language type:
CLU is a compiled imperative language
with extensive features for defining and
employing abstract data types. It was
intended for general application development,
and also as a research vehicle in computer
As was a descendant of Algol, CLU
offered syntax that was similar to Algol60
in many respects, but it added
data type abstraction, exception handling,
and other advanced features.
The name "CLU" is short for "CLUster",
this was chosen because a CLU program
consists of procedures, clusters, and
CLU supported a number of advanced
features for structured languages for its day,
including garbage collection, a form of
strong typing, generics, and exception
The research operating system SWIFT
was written in CLU, as were other tools
A free CLU compiler named 'PCLU' is
available from MIT. There is also a
CLU->C translator named clu2c available
from Tokyo Tech. Some information about
CLU is available on the web, but not much.
B. Liskov et al, 1974-77.
- See Also:
CLU was mostly a research vehicle for
experimenting with data abstraction
and other language design issues.
Some of its ideas, especially in the
area of exception handling,
have been adopted in
newer languages like Ada and Java.
The ideas for CLU were derived from a
programming methodology, also defined by
Barbara Liskov and her colleagues, that
emphasized abstract data types and
While CLU is syntactically similar to Algol,
its data storage semantics are more like
those of mainstream Lisp (and, much later,
Java). All objects in a CLU program live
in the heap, and memory management is
automatic. This sort of a approach does
eliminate much of the semantic complexity
associated with multiple forms of
programmer-managed object storage observed
- Sample code:
% Driver and function to compute factorials
% from the PCLU distribution.
start_up = proc ()
pi: stream := stream$primary_input()
po: stream := stream$primary_output()
while true do
stream$puts(po, "Enter an integer (or RETURN to exit): ")
s: string := stream$getl(pi)
if string$empty(s) then break end
n: int := int$parse(s)
except when bad_format:
stream$putl(po, "Illegal integer")
stream$putl(po, int$unparse(n) || "! = " || int$unparse(factorial(n)))
except when negative:
stream$putl(po, "Integer must be positive")
factorial = proc (n: int) returns (int) signals (negative, overflow)
if n < 0 then signal negative end
if n = 0 then return(1) end
Descriptions in this dictionary are ©1997-99 Neal Ziring. Some
examples copyright of their respective authors. Some
technologies and languages are trademarked. Permission to
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Dictionary and script maintained by Neal Ziring, last major modifications 3/18/98. Most recent
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