Recent content by Christophe Lenclud

  1. C

    Deciphering GW-BASIC / BASICA protected programs

    Purpose We describe the deciphering algorithm needed to unprotect source programs stored by GW-BASIC / BASICA.COM. History Microsoft BASIC interpreters were a common way of programming early IBM PC and compatible computers (1981 onwards). Several versions of Microsoft BASIC were used: first IBM...
    • Christophe Lenclud
    • Thread
    • basic basica decipher gw-basic microsoft ms-dos protected files source code obfuscation tokenized basic xor
    • Replies: 0
    • Forum: Papers
  2. C

    Detecting a signedness bug in vintage compiled Pascal programs

    The bug We previously reported that MASM.EXE version 1.00, a program published in 1981 by Microsoft and IBM for MS-DOS, hangs or exits when run with some precise free memory amounts. We showed that this is due to a signedness error in the stack setup code emitted by the compiler. All other...
    • Christophe Lenclud
    • Thread
    • assembly language debugging masm ms-dos pascal pc history signedness error
    • Replies: 0
    • Forum: Papers
  3. C

    Debugging IBM MACRO Assembler Version 1.00

    Debugging study by Dr Christophe LENCLUD, April 2017 "The IBM Personal Computer MACRO Assembler", also known as MASM, published by Microsoft and IBM since 1981, was one the firsts Assembler programs to run under MS-DOS / PC DOS on IBM PC or compatible computers. Lot's of code was written for...
    • Christophe Lenclud
    • Thread
    • assembly language debugging ibm masm integer overflow ms-dos pascal signedness error
    • Replies: 0
    • Forum: Papers
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