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News:
At long last, an update to my cryptography pages!
A description of the Abwehr SG-39, which was
similar to an Enigma, but with a pinwheel assembly controlling the rotor stepping,
has been added to the page on relatives of the Enigma,
and a description of the SG-41 has been
added to the page on Hagelin machines.
The page on computer arithmetic, as it
contained a list of alternate versions of hexadecimal notation used on early computers,
now has had duodecimal characters, and some early character sets with characters for
pence in sterling currency, added; one of those character sets, used on the Elliott 503
computers, is Cluff-Foster-Idelson code, which anticipated ASCII. On both that page,
and the page about punched card codes, I've also added
a reference to the GOST 10859 code from the former Soviet Union.
The former of those two pages now also exhibits the character coding for the STRETCH (IBM 7030)
computer, as that code, like GOST 10859, has many of the special characters originally
used for ALGOL. The IBM 7030 code had the unusual characteristic of putting the upper-case
and lower-case letters of the alphabet in the sequence aAbBcC... in the vain hope of
simplifying collation; and so I've also included in the diagram for it an image of the
ARMSCII code, which placed the letters of the Armenian alphabet in AaBbCc... style order.
As well, I've made
some changes to the diagrams on this page, about modifying
ASCII, and a diagram of FIELDATA has finally been added
to this page.
An attempt has been made to unravel the mystery of
the tone generator used for the chorus feature of the model BC, D, and E
Hammond organs on
this page. RECENTLY UPDATED, thanks to my having been
able to see a photo of part of a chorus tone generator.
The page about building blocks
and the Pythagorean triangle has been
updated showing two ways in which additional directions of walls could be added with
alternate block types.
Several updates have recently been made to the section on Chess, among them:
A page
describes a number of the systems for recording the moves of a Chess game,
including several quite obscure ones.
The description of Korean Chess
has been corrected and extended.
Most recently, yet another variant
form of Chess has been added, placing the King and Queen off center to better preserve
Castling on an enlarged board, and proposing an interesting use for a second King.
A new page has been
added discussing memory interleaving techniques.
The apparently contradictory conditions for the
efficient use of data elements the lengths of which are not in a
simple power-of-two relationship have now been reconciled. On
this page I explain how, after dividing a
256-bit memory word into five or seven parts (for 51-bit intermediate-precision
and 36-bit single-precision floating-point numbers), I can then, at the cost
of a small amount of additional wastage of storage space, calculate physical
addresses efficiently without resorting to division by five or seven.
As well, several portions of the section on
A Computer Architecture have been
modified, both to incorporate this added feature, and to incorporate the feature
of selectively saving or updating condition codes to allow speculative execution
to be avoided.
Also, a 12-bit oriented example architecture,
fleshed out in more detail than the previous 12-bit example in that section,
has been added to the section on dealing with nonstandard lengths of data.
The section on basic HTML has been extended with
a page about the use of Cascading Style Sheets
for formatting.
Two early computers from the People's Republic of China are now mentioned on this
site: a description of the instruction format of the 757 vector computer has been
added to the section on 32-bit computers, and a description of the
instruction format of the DJS-21 computer has been added to the next
page.
The section describing the Fast Long Single and Fast Intermediate modes
of operation has been moved to its own page, and has been
revised and extended.
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