Cryptography Reference
In-Depth Information
from U.C. Berkeley in 1973, but worked at Xerox PARC from 1970 to 1986.
In 1986, he began writing the ghostscript 10.15 program. From 1986 to 1991 he
was employed at ParcPlace Systems. He has been at Aladdin Enterprises since
1991.
Knight : Knight, Greenblatt, and others created the Incompatible Time
Sharing System (ITS) at the MIT AI Lab in the late 1960s. It was written in
Assembly Language and run on DEC's PDP-10s at MIT until 1990 after which
it was run at the Stracken Computer Club in Sweden until 1995. The ITS was
the first device-independent graphics terminal output; required no password to
log on; any user could crash the system, and a message was sent to tell who that
was; all users could converse with instant messaging on the terminals of others;
and users could watch what was happening on any other user's terminal. These
and numerous other truly revolutionary features were incorporated and later
used in other operating systems. Even some aspects of GNU/Linux were begun
on ITS. Knight was also involved in the development of the Lisp machine at
MIT, which came to be the hacker's favorite machine. Currently, Tom Knight
is a senior research scientist at the MIT AI Lab.
Sussman Gerald J. Sussman co-invented the scheme programming lan-
guage, which is a descendant of Lisp. He is famed for his topic, co-authored
with Hal Abelson, Structure and Interpretation of Computer Programs , which
has become a classic (see [1]). It was used in MIT's introductory computer
class for majors, 6.001, developed by Sussman and Abelson, which was taught
in scheme. The topic [1] has become known as the Wizard topic , with legendary
characters from it and the 6.001 class emerging, such as “Alyssa P. Hacker”,
“Louis Reasoner”, and “Captain Abstraction”.
The Second Wave : The “second wave” of hackers were largely based
on the west coast, but many such as Stallman, had their beginning at MIT. The
west-coast center for this second wave was the Sanford University AI Lab, called
(Programmable Data Processor), series produced in 1960. They were famous both for being
ground-breaking, and for being influential in creating the hacker culture at MIT.
10.15 Ghostscript is a PS (PostScript) and PDF (Portable Document Format) translator. This
means it is a program inputting a PS or PDF file and generating an alternative-format repre-
sentation of it as output. Ghostscript is freeware released in two versions: one for commercial
use as AFPL (Aladdin Free Public License) ghostscript; and GNU GPL (General Public Li-
cense) ghostscript. The GNU GPL is a copyleft free software license , which is a product of
the GNU project from 1988. Copyleft is an application of the copy right law whose purpose
is to force derivative works to be released with a copy left license as well. What this means
is that any number of individuals may make successive improvements, but those who refuse
the terms are not allowed to create derivative works. Derivative work is work based upon
preexisting work. With respect to software this includes a translation of a computer pro-
gram into another language or conversion of an existing program onto a new platform. The
derivative work is separately copyrightable, but applies only to the new work added as well
as any amalgamation of the new and old parts of the work. Stallman created the copyleft
concept after he supplied a public domain version of his Lisp interpreter to Symbolics, who
made improvements to it. When Stallman asked for access to those improvements, Symbolics
refused. In 1984, he created a software license to prohibit such behaviour, whence the copyleft
idea, to thwart what Stallman called “software hoarding”. Think of the purpose of copyleft,
with respect to freeware, being to ensure that derivatives of licensed work remain free.
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