Showing posts with label Fortran. Show all posts
Showing posts with label Fortran. Show all posts

Saturday, April 19, 2025

Bill Gates’s Source Code

Source Code is the title of Bill Gates’s autobiography. It also the eponym for the work that he, Paul Allen, and Ric Weiland did for Ed Roberts’s Altair 8800. Written on a teletype connected to a Digital Equipment PDP-10, their first task was to create a simulator of the Altair 8800 on the PDP-10. Then they wrote the source code for Altair BASIC. The BASIC interpreter was the product that Gates and Allen promised Roberts. In legendary hacker style, they did the work in under a week in bursts of long overnight sessions. 


For myself, reading through it, I enjoyed contemplating the roots of modern computer programming but really understanding it at that level would have required more effort than they put into it. So, I left it like a trip to an art museum: spend time understanding the work, but I will never create anything like it.

 


Note that the nested line numbers along the wide left side show that the publication is an archive:. a file saved later as a new file.

 

https://images.gatesnotes.com/
12514eb8-7b51-008e-41a9-512542cf683b/34d561c8-cf5c-
4e69-af47-3782ea11482e/
Original-Microsoft-Source-Code.pdf
 

The source code is commented at the right. 

https://images.gatesnotes.com/
12514eb8-7b51-008e-41a9-512542cf683b/34d561c8-cf5c-
4e69-af47-3782ea11482e/
Original-Microsoft-Source-Code.pdf

Also, in the story from Bill Gates, they had some discussion about whether to create an interpreter or a compiler. BASIC was intended as an interpreter so that each line could be debugged while written and run instead of writing, compiling the whole program, and then debugging the inevitable errors, as with Fortran or Cobol. 

 

The power in the interpreter for learners is that feedback is immediate. It is also true that at some level of complexity and volume, having the entire program in a body is convenient and we spent hours reading and debugging long programs on accordions of greenbar paper and carrying around decks of punched cards. 


While it was possible to Save a program under a filename, the fact is that such resources were not often available for those high school and college learners of 1969 to 1989 because disk drive space was expensive. Today, I am going to the Apple store to pick up a new iMac with a terabyte of onboard memory. When I took Fortran in 1976 at Lansing Community College, the whole town - Michigan State University, General Motors, and the State of Michigan - did not have a billion billion bytes of storage. 

 

PREVIOUSLY ON NECESSARY FACTS

Fortune Cookie in Hex Code 

John Kemeny Knew: We Shall Have Computed 

BASIC: Turing’s Truth 

Claude M. Watson 

 

Wednesday, June 26, 2013

BASIC: Turing's Truth

Alan Turing showed that any finite-state machine can model any other.  That is how the team at Bletchley Park built the Bombe to imitate the German Enigma machine.  Today, we have “virtual machines” that let us put Unix and Windows on a Macintosh or Linux and Windows on a PC and so on.  The C language is actually an extension of itself, a realization by Kerninghan and Ritchie that inherent extensibility would allow programmers to create a language that would never become archaic.  And today we have C+, C++, and C#.  In fact, Ruby is just a set of macros written in C.  Once you have that, you can create your own Ruby objects, classes, and methods.  
 
Book cover shows silouette of man behind computer's punched card

The “Venture Rocket” blog presented a cute history of computer languages.  While one graphic did acknowledge Visual Basic as the seventh most popular development language, their history below that ignored Basic entirely. (They did cite Fortran and Cobol.) 

Earlier this month, I answered a challenge from the Praetorian computer security company to decipher this block of text.

Mpyza johsslunl ZWXY, Zluhabz Wvwbsbzxbl Yvthubz (Aol Zluhal huk Wlvwsl vm Yvtl), aolzl hyl aol budhclypun hsslnphujlz vm Aol Wyhlavyphu Nbhyk, luaybzalk if Jhlzhy av wyvcpkl aolpy lspal zljbypaf zlycpjlz huk luzbyl aol zhmlaf vm aol nsvihs Yvthu Ltwpyl. Hz aol zhfpun nvlz, "Hss Yvhkz Slhk av Yvtl", ovdlcly aol whao vm h Wyhlavyphu pz ulpaoly zayhpnoa uvy klalytpuhal. Aolyl hyl zlclyhs whaoz av qvpupun aol Wyhlavyphu Nbhyk, iba aol whao dlss-mvbuklk pu tlypa pz aol tvza ovuvyhisl. Pa pz mvy aopz ylhzvu aoha Jhlzhy ohz klcpzlk aopz zlyplz vm johsslunlz av qbknl aol tlypa vm wvaluaphs Wyhlavyphu yljybpaz. Fvb ohcl wyvclu fvbyzlsm ylzvbyjlmbs, iba kvu'a sla fvby nbhyk kvdu hz mhy tvyl kpmmpjbsa johsslunlz spl holhk. Av hjjlwa fvby ulea johsslunl, fvb dpss ullk av zluk tl h tlzzhnl vu Zrfwl. Av hkk tl hz h jvuahja, zluk h jvuahja ylxblza jvuahpupun aol alea "Zluhabz Wvwbsbzxbl Yvthubz" av "wyhlmljabz.jhzayvybt", aolu zluk tl h joha tlzzhnl av sla tl ruvd fvb'yl aolyl. Zll fvb vu aol ihaaslmplsk.

To do that, I wrote this program in BASIC.

10 REM Mike Marotta. June 21, 2013. Praetorian challenge.
11 REM: Claudic.bas compares cipher with known transposed key
12 REM: prints deciphered text
15 ON ERROR GOTO 199
20 P1$ = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
22 C1$ = "TUVWXYZABCDEFGHIJKLMNOPQRStuvwxyzabcdefghijklmnopqrs"
40 OPEN "i",1,"praeto.txt"
42 OPEN "o",2,"plain.txt"
50 LINE INPUT #1, X$
53 E = LEN(X$)
60 FOR I = 1 TO E
62 Q$ = MID$(X$,I,1)
63 REM Accept punctuation as is
64 IF ASC(Q$)<65 THEN PRINT#2,Q$;:
70 FOR J = 1 TO 52:
73 IF Q$=MID$(P1$,J,1) THEN PRINT#2, MID$(C1$,J,1);
80 NEXT J
85 NEXT I
90 GOTO 50
199 CLOSE 1: CLOSE 2
200 END

The program returned this decipherment.

First challenge SPQR, Senatus Populusque Romanus (The Senate and People of Rome), these are the unwavering allegiances of The Praetorian Guard, entrusted by Caesar to provide their elite security services and ensure the safety of the global Roman Empire. As the saying goes, "All Roads Lead to Rome", however the path of a Praetorian is neither straight nor determinate. There are several paths to joining the Praetorian Guard, but the path well-founded in merit is the most honorable. It is for this reason that Caesar has devised this series of challenges to judge the merit of potential Praetorian recruits. You have proven yourself resourceful, but don't let your guard down as far more difficult challenges lie ahead. To accept your next challenge, you will need to send me a message on Skype. To add me as a contact, send a contact request containing the text "Senatus Populusque Romanus" to "praefectus.castrorum", then send me a chat message to let me know you're there. See you on the battlefield.

Of course, this is merely a transliteration.  I already broke the cipher.  I found the common three-letter words, and guessed “the.”  I also guessed that the longest word would be “Praetorian” which then validated two of my letters in “the.”  All I wanted to do next was avoid the grunt work of writing out the answer. Computers are good for that.

Previously on Necessary Facts