ShareWare OnLine 2/ShareWare OnLine Volume 2 (CMS Software)(1993).iso/database/magrak18.zip/MAGRAK.DBT

dBase/FoxBase/XBase/FoxPro Database File | 1993-03-06 | 15KB | 171 lines

  Getting the most out of your graphics adapter with
  video memory remapping.
    Graphics resolution and color are attractive features
  of the VGA, but some of their other useful features
  are often overlooked.  The ability to pan the screen
  image both horizontally and vertically can greatly expand
  EGA/VGA's usefulness.  This article explains how to remap
  the video memory to allow this kind of pixel panning.

  Powerful hardware tools for complicated problem solving
  The software-only debuggers that come with assemblers and
  compilers are usually designed for solving problems at the
  applications level.  Although some of these products can
  also help debug terminate-and-stay-resident (TSR)
  programs, it is difficult or impossible to use them when
  debugging problems involving device drivers, hardware
  interrupt service routines, real-time interactions
  between two or more programs, or a hung system.
  Hardware-assisted debuggers use a combination of
  hardware and software to enable you to solve these more
  complex kinds of problems.  Levels of hardware assistance
  in these debuggers include a break-out switch, protected
  or hidden memory, real-time breakpoints, and a real-time
  trace buffer.

  Writing Portable code to access SCSI devices using the
  Common Access Method.
    The ANSI-standard, high-speed I/O bus known as the
  SCSI (Small Computer System Interface) is supported by
  an unprecedented variety of computers and peripherals.
  If you own a Mac, a Sun, a NeXT, or an Amiga with a hard
  disk, you're probably already using SCSI, whether you
  know it or not.  The smae is true if you have a PC clone
  with a Bernoulli box, a CD-ROM, a magnetopoptical disk,
  or a WORM drive.

   When you need more speed and greater capacity.
      As one of the programmers at a developer of CAD
   software for printed circuit-board design, I was
   assigned the job of porting our CAD programs from
   Microsoft C 4.0 to an 80386 protected-mode compiler.
   After making a quick study of the three Microway, High-C
   386 from MetaWare, and Watcom 7.0/386 from Watcom-- we
   chose the Watcom compiler.  This article describes the
   problems and solutions we encountered in the process of
   porting 75,000 lines of C.
  Detect memory allocation errors automatically.
    Originally the program was small, less than 20,000
  lines, and command-line driven.  But after two years,
  four different programmers, and the addition of a lot of
  functionality -- a nifty graphical user interface,
  multiple printer support, foreign language menus, and
  a kitchen   sink -- the program grew to 150,000 lines.
  Then it started CRASHING.
  The unique features of this special-purpose language can
  greatly improve development time.
    The AWK language is one of the gifts that the Unix
  environment has given to us.  Named for the intials of its
  developers (Alfred Aho, Peter Weinberger, and Brian
  Kernighan), AWK was originally designed to be a simple
  utility for "quick and dirty" programming tasks.  Since
  then it gradually evolved into a powerful tool capable
  of performing many time-saving tasks for programmers.

  Drawing objects that contain curves.
    Lisp is an excellent language for developing
  high-level AI programs.  In particular Allergro Common
  Lisp (Allegro CL) has made the McIntosh an excellent
  platform for developing AI software.  All implementations
  of Common Lisp including Allegro CL, are limited by some
  serious drawbacks.  Commnuications to graphics and audio
  devices are not specified and Common Lisp does not even
  define access to physical devices.  (A trap mechanism in
  Allegro CL does permit communication to the MacIntosh
  Toolbox, but this mechanism is very limited.) Additionally,
  complex mathematical computations, such as geometric
  transforms or statistical analysis, are extremely slow
  in any implementation of Lisp.
  Taking advantage of variable argument lists in C.
    While writing my first serious financial program in C
    (I'd previously used the language only for utilities),
    I was distressed by the lack of suitable output
    formatting -- specifically, comma-separated numbers
    with trailing signs.  After working with Cobol
    financial applications several years, I expected such
    niceties from any language.
  When your text-based application can no longer deal with
  the memory-hungry real world, it's time to go virtual.
  Stephen shows you how to select and develop an
  application-supported virtual memory system that can take
  advantage of EMS paging and disk storage.
  John examines string hashing functions for fast table
  lookup and explains why a hash table, unlike your car's
  gas tank, should never be full.  He also creates
  equivalent functions in assembly language for Windows 3.0
  routines that manage handle-based dynamic storage and
  atoms (hashed strings).
  Installment21: In which we carry on with VGA color.
  When last we left our hero, he/she (take your pick) had
  learned how to set the VGA's Digital to Analog Converter
  (DAC) to select 16 or 256 colors from a set of 256k
  colors.  However, there was still a great deal to learn
  about color paging, loading and reading the DAC, and
  color cycling, so that's the direction we're headed
  next.  Before we begin, though, let me clear up a
  potential problem with C code from earlier installments.
  In the old days, a reasonable C preprocessor read an
  input file, discarded comments and excess white space
  (spaces, tabs, and new lines), built tokens (character
  sequences), substituted definitions, and expanded macro
  definitions.  It didn't care when expansions and
  substitutions were done.  Probably the most challenging
  aspect of the preprocessor was handling macro expansions
  and argument substitutions in a constrained memory space.
   The PC presented two problems: segmented memory
   architecture due to the Intel microprocessor's 64k-byte
   maximum segment size and DOS's 640K maximum memory size.
  My own perspective is that one learns more from 'details'
  that from generalities.  Lots of articles and books cover
  material at the general level, so this article will focus
  on the details--how b-tree indexing is implemented in
  several dbase-compatible products.  My interest is not
  solely acedemic, but stems also from several years of
  real-world database programming conducted for the the
  State of Oregon.
  A few years ago language vendors predicted their
  compilers would soon generate code  that would be nearly
  as efficient as assembly language code.  They were wrong.
   C is a great programming language.  It's complicated
   enough to scare away beginners, fun to program, and
   efficient.  Of course, assembly language is more is more
   complicated, more fun, and more efficient.  With due
   respect to Watcom, Micrsoft C is about as good a 80x86 C
   compilers get.  Bill Gates spends more dough on his C
   compiler than anyone else, yet it doesn't touch assembly
   language.
  One of the more appealing features of the VGA is the
  ability to display 256 simultaneous colors.
  Unfortunately, one of the less appealing features of the
  VGA is the limited resolution (320 X 200) of the
  256-color mode the BIOS supports.  More color can often
  compensate for less resolution, but the resolution
  difference between the 640 x 480 16 color mode and the
  320 x 200 256 color mode is so great that many programmers
  must regretfully decide that they simply can't afford to
  use the 256-color mode.
  Writing a terminal emulator in Windows offers many
  chalenges not normally encountered in the character-based
  DOS world.  But if you can overcome the sometimes
  surprising difficulties, you can reap many benefits: a
  rich user interface of dialog boxes and menus,
  multitasking and data exchange with other applications,
  the ability to implement special-purpose fonts, and a
  communications device driver with a complete set of
  function calls.
  Now matter what the language, we all strive to create
  programs that execute in the least amount of time while
  using the fewest number of bytes.  Unfortunately, many
  programmers who use a high-level language have no way to
  determine which statements are the most efficient.
    The purpose of this article is twofold.  We will
  discuss various BASIC statements to see which ones are
  faster and smaller.  Then we will examine the actual
  machine instructions generated by QuickBasic 4 and compare
  them with the original BASIC source code.
  The ability to overlay large applications is taken for
  granted by most modern software developers.  Thus, the
  usrs of Borland International's Turbo Pascal were quite
  shocked to discover that a built-in overlay capability
  present in Release 3 was missing from Relaease 4.