budd@arizona.UUCP (tim budd) (01/23/85)
An interpreter for a Smalltalk-like language is now
available from the University of Arizona. The system, known
as ``Little Smalltalk'', is written entirely in C, and does
not require any special hardware beyond conventional ascii
terminals. Unlike Smalltalk-80, Little Smalltalk is not a
complete programming environment, but sits on top of Unix
and uses the Unix file system and Unix editors. It is
intended to provide an introduction to some of the concepts
of Smalltalk (such as object oriented programming and inher-
itance) for individuals (particularly students) who do not
have access to the more modern hardware required for
Smalltalk-80.
The language recognized by the Little Smalltalk system
is similar, although not identical, to the Smalltalk-80
language described in the book by Goldberg and Robson. The
elimination of the bit-mapped display and the mouse permit-
ted the removal of much of the graphics kernel. Other
changes were made in the interest of reducing size or sim-
plifying the implementation. Among the most notable differ-
ences are:
* No mice - no browser, none of the nice environment
described in the orange book
* Fewer classes, many of the classes in the blue book
have been eliminated for space or implementation rea-
sons.
* No class methods - all classes respond to the same set
of messages
* Instance variables have scope restricted to the class
in which they are defined.
* No indexed instance variables.
* No pool variables (instead, there is a single global
dictionary the user can access).
* Cascades have been redefined to make them easier to
understand and more like expressions.
* Internal representation is totally different from that
of the blue book.
All these differences, and much more, are explained in
detail in the documentation distributed along with the dis-
tribution tape.
Currently, the system has been ported to the following
systems:
* VAX 780 / Berkeley 4.2
* PDP 11/70 and 11/44 (using separate I/D)
* Ridge / ROS 3.0
* DecPro 350 (using code mapping feature)
As evidenced by the implementations on the 11/70 and
the DecPro, size requirements for the system are not large,
although it would probably not fit on a pure 64K address
space.
The system is totally independent of the Xerox virtual
image, and in fact has been produced using only the descrip-
tion provided by the blue book.
The little Smalltalk system can be obtained by sending
a check for $15 (US) payable to ``The University of
Arizona'', to the following address:
Timothy A. Budd
Smalltalk Distribution
Department of Computer Science
The University of Arizona
Tucson, Arizona
85721
Please specify along with your request your name,
address, electronic mail address, the type of computer you
will be using and its operating system. Source is distri-
buted in 9-track tar format, preferably 1600 bpi.