TurboC Usage

Porting Borland Turbo C source code to GNU gcc

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"Sister Talk" by Lynn Rothan


Using TurboC
Running a ported program
Running a ported program remotely
Supported Turbo C entities
Handling of integer datatypes
Special-function keys
Text screen resizing
Graphical display characters in text mode
Graphics mode
Alternative graphics-mode functions
Endian conversions


No explanation of the exact functionality of the various TurboC library elements is offered here, except for noting differences between Borland's version and my version.  As Pablo Vidal points out on his UConio web page, if you don't know how to use these functions already, then you won't need the TurboC library, since you shouldn't be using it for new program development anyway.  Consult Borland's Turbo C Reference Guide as needed.

But if you are porting or supporting a Turbo C program that somebody else has created, and don't have access to Borland's printed materials yourself, I'd offer the following advice:  Download the free Turbo C development environment that Borland has kindly provided on their "museum" website.    (Requires you to register, but registering is free.)  The IDE has context-sensitive help, and you can find out what most functions do by typing the name of the thing (such as clrscr)  into the source-code editor and then hitting ctrl-F1.  Of course, this requires you to have some means of running an MS-DOS program.

Alternately, the online help for Borland's C++Builder program actually provides much fuller documentation of Turbo C library functions (even though it doesn't support a lot of them), and while C++Builder itself is not free, Borland allows you to download the Win32-based helpfile for free from their website .   After you download it, the particular helpfile you want is the one which Borland calls the DOS Reference.  Sadly, there's no guarantee that this documentation corresponds exactly to the functionality provided in Turbo C.

Using TurboC

Compile the Turbo C source you're trying to port, using GNU gcc. Add command-line switches to link to TurboC, to ncurses, to Xlib , and to pthreads:
gcc [-O0] ... your switches ... -lTurboC -lm -lncurses -L/usr/X11R6/lib -lX11 -lpthread
gcc -DDoNotFixIntegers ... your switches ... -lTurboCu -lm -lncurses -L/usr/X11R6/lib -lX11 -lpthread
In FreeBSD, you'll have to say "-lc_r" rather than "-lpthread".  Note that the actual directories containing header files and libraries of the X-window system may vary, so you may need to alter the "-L" switch or add a "-I" switch to access the appropriate X files.

The command-line switch "-DDoNotFixIntegers" is optionally used to turn off TurboC's integer datatype conversion macros and (as you may notice) uses a slightly different version of the library.  In the past, some GNU "functions" actually implemented as macros have failed to compile with optimization level higher than -O0, when integer datatype conversion is turned on.  That's why one of the examples includes -O0 and the other does not.  However, this precaution is probably no longer necessary, and you needn't use -O0 unless experiencing problems.

You can see samples of both types of compilation in the provided Makefile.  If there are complaints from the compiler, refer to the trouble-shooting section below.

The switch "-lm" is required by only a couple of functions, but there's no harm in using it for everything.  The switch "-lncurses" is needed only if you are using the Turbo C functions prototyped in conio.h, while the switches "-L/usr/X11R6/lib -lX11 -lpthread" are needed only if using the functions prototyped in graphics.h.  You'll want to remove these switches if they're not used, to enhance your ability to compile the ported program on more platforms.  For example, neither ncurses nor Xlib are typically present in a Mac OS X system (though they can be installed with some effort), and compilation of your ported program will therefore typically fail if these compiler switches are included.

Although I'm not entirely sure why you'd want to do it, and though I haven't tried it myself, I think you can probably disable the graphics.h functions in the TurboC library, and replace them with those in the GRX 2D graphics library.  In the TurboC library Makefile, remove the compiler switch "-DWITH_X" before compiling the TurboC library.  Then install GRX and follow the instructions in GRX's readme.bgi file.  I'd be happy to hear from anyone with feedback (pro/con/howto) on this topic, and will post those comments if they seem to be of general interest.


Since TurboC is provided under the LGPL , you are free to license your own program however you like.  In other words, your program does not have to be GPL'd.  Of course, it would be nice to do so, and you might want to consider GPL'ing your code.  You'll still want to read the LGPL to make sure that you conform to its (rather minimal) requirements.

If your code is linked to ncurses or X, as described in the previous section, you'll also have to conform to their licenses, namely the MIT license and the X-Consortium license respectively.  These licenses are highly non-restrictive, and require merely that you include their copyright notices.  Both licenses can be viewed at the Free Software Foundation's website.

Running a ported program

The ease with which you can run a program ported to *nix with the TurboC library depends on which Turbo C capabilities have been used.  The important points to consider are whether the "console i/o" capabilities (as represented by the header file conio.h) and/or the "graphics" capabilities (as represented by the header file graphics.h) have been used.

While text-based programs ported with the TurboC library run to some extent in almost any *nix text terminal, it is highly advisable to run the ported program under the X-window system, explicitly using xterm.  I'd recommend invoking your program as follows, either from a command line or as a desktop icon:

xterm +sb -tn linux -e PortedProgram PortedProgramOptions ...
(See "man xterm".)  The "+sb" command-line switch removes scrollbars from the xterm console.  The "-tn linux" command-line switch insures that the xterm color settings, function-key interpretation, etc., match what's used in Linux (where I've been developing the TurboC library).  This is useful, for example, if the ported program is being run in FreeBSD, where xterm's default settings aren't necessarily the same as in Linux.

The deficiencies which you may encounter if xterm is not used are numerous, but other kinds of text consoles (even a real text console without the X-window system) may prove to be satisfactory for your purposes.  You'll simply have to try it and see, if you're so inclined.

Graphical capabilities, on the other hand, are supported only under the X-window system, and require availability of an X server.  In general, this means that the ported program can be run on any *nix box except bare-bone ones (like firewalls) or quirky ones (like Mac OS X) that don't provide X.

Running a ported program remotely

Because text-handling capabilities of the TurboC libary are based on standard i/o streams (stdin/stdout) and on ncurses, the text-based programs work just fine when run remotely but hosted on another computer:
xterm +sb -tn linux
telnet/rlogin/ssh/etc. (to connect to host)
PortedProgram PortedProgramOptions ...
Actually, there is some difficulty correctly sizing the screen when ssh is used for the remote login, though telnet and rlogin seem to work properly in the cases I've tried.  What happens with ssh is that if the xterm window is manually resized, it doesn't automatically resize itself until a key is pressed.  I imagine that the desire to remotely run a ported Turbo C program is rare, so this is unlikely to pose a problem for many people.

To a certain extent, graphically-based programs can also be run remotely, because the TurboC library's graphical capabilites are based on the X-window system.  However, exploiting this capability is hardly a user-friendly process.  The following steps are necessary:

  1. You must set up the X-server at the user's location to accept input from the remote computer hosting the ported TurboC program.  This is done with the command-line program xhost, and you need to know the ip address of the remote computer:
  2. The DISPLAY environment variable must be properly initialized on the remote computer to indicate the user's computer.  Typically this is done automatically when you log in (with telnet/rlogin/ssh ), but not necessarily.  So after logging in, but before running the ported program, you might need to set up DISPLAY.  In the bash shell, this would look something like this:
    1. export DISPLAY=UserIpAddress:0.0
Putting it all together, the complete sequence of steps for running the program remotely might become something like this:
xterm +sb -tn linux
xhost RemoteIpAddress
telnet RemoteIpAddress
export DISPLAY=UserIpAddress:0.0
PortedProgram PortedProgramOptions ...
Unfortunately, firewalls and/or network-address-translation may wreak havoc with this scheme, and you may find that the graphics capabilities of the ported Turbo C programs simply don't work remotely.  Text-only ported programs are fortunately less affected (i.e., not affected)  by these problems.

Supported Turbo C entities

Of course, there are a lot of functions in Turbo C that are not only supported in GNU gcc, but that are even supported identically, such as fopen , fclose, fread, printf, time, etc.  On the other hand, a generic function like putchar may operate similarly only over a certain range.  For example, putchar(0xA5) is unlikely to display characters that appear to be identical in Borland Turbo C on an IBM PC and in GNU gcc in Linux.  I'm sorry about that, in a theoretical way, but life is too short for me to expend a lot of energy fixing it.

Anyway, the table below isn't a complete list of all the Turbo C entities you can use, but simply those that the TurboC library treats specially. Also, I'm sure there are Turbo C functions that need special treatment which I've simply not encountered yet in my porting activities, and so aren't included here.

Turbo C Entity Entity Type Supported Notes
__libTurboC__ constant n/a Provided by the TurboC library, but not normally present in actual Turbo C.  Can be used with conditionaly compilation to insure that any changes you make to your code in porting to libTurboC are discarded if the program is recompiled later in actual Turbo C.  :-)
alloc.h header file Yes This is supported in the sense that a file of this name is provided.  However, not all of the functions are necessarily supported.
arc function Yes
bar function Yes
bar3d function Yes
bios.h header file Yes This is supported in the sense that a file of this name is provided.  However, not all of the functions are necessarily supported.
biosprint function Yes Thanks to Igor Bujna!  At the moment, this one relies on Linux specifically (not FreeBSD or other Unices). 
BypassResizeXterm variable n/a This is not present in real Turbo C.  Normally, the TurboC library will attempt to physically resize the text console when you call textmode .  However, this does not work unless you are running xterm.  If you set BypassResizeXterm to a non-zero value before calling textmode-- say, on the basis of some environment variable setting -- then the attempt to resize the window is bypassed.  However, the window must still be resized by some other mechanism or else the program may segfault.
cgets function Yes
circle function Yes
cleardevice function Yes
clearviewport function Yes
clock function Yes This is already a standard *nix function, but the existing *nix function is not suitable for Turbo C.  Instead the existing function is rename clockUnix and a new clock (clockTurbo) function is created. The CLK_TCK constant may also pre-exist in *nix, but it may (or may not) be assigned a different value than needed for clock .  If TurboC.h or any other header files from the TurboC library are included, CLK_TCK will automatically be reassigned (within that source file) to an appropriate value.  However, it may not be the same value for CLK_TCK used in true Turbo C (variously, 18 or 1000).  For example, in my experiments it is equal to 100, but there's no guarantee that it won't be 1000000 on some system.  This means that the output of clock must always be assigned to a variable of type clock_t , because it may overflow an int or unsigned clock and CLK_TCK are supposed to be prototyped in time.h -- and are -- but won't have the behavior expected in TurboC unless a TurboC library header file is included also.  In other words, if time.h is included but no TurboC header file is included, clock will behave incorrectly but there will be no errors or warnings.  Finally, clock is supposed to measure the time since program startup, but in TurboC it actually measures the time since clock itself was first called by the program.
closegraph function Yes
clreol function Yes
clrscr function Yes
COLS variable n/a This is not present in true Turbo C.  It is an ncurses variable that tells the current number of text columns in the display console.
conio.h header file Yes Most conio.h functions are supported.  Currently, only cscanf is omitted.  Support is through ncurses.
ConioResizeCallback function n/a This is not present in true Turbo C.  It is a function which the TurboC library calls when it has detected that the user has resized the console.  By default, it does nothing, but you can override this behavior by providing your own version of this function (which will be preferentially chosen at linktime over the version already within the TurboC library).  You can do anything you like with this function, but one possible use is to refresh all of the text data on the screen.  Use the LINES and COLS variables to determine the current screen height and width.
cprintf function Yes
cputs function Yes
cscanf function No It may seem naively that this function is a simple combination of cgets with sscanf.  However, on closer inspection it really isn't.  I don't presently see how to implement it without messing with the guts of the scanf function family (which I have no desire to do). 

Workaround:  For the present time, I'd suggest writing cscanf out of your code in favor of cgets and sscanf .  Actually, I've seen Borland docs that recommend this also.

struct date data type Yes Thanks to Igor Bujna.
delay function Yes (Igor Bujna provided this function but I haven't used it, because his version relies on ncurses.  Thanks but sorry, Igor!) The function parameter has arbitrarily been changed from 16-bit to 32-bit.
delline function Yes
detectgraph function Yes
dir.h header file Yes This is supported in the sense that a file of this name is provided.  However, not all of the functions are necessarily supported.
variable Yes I provide variables of this name, which you can manipulated as desired, but they don't affect any conio functionality.  (It seems to me that variables of both names have been provided in different versions of Turbo C, but they behave the same.)
dos.h header file Yes This is supported in the sense that a file of this name is provided.  However, not all of the functions are necessarily supported.
dostounix function Yes Contributed by Igor Bujna.
drawpoly function Yes
ellipse function Yes
far type modifier Yes Requires TurboC.h.  There's no need for "far pointers" with a 32-bit compiler, so this is simply an empty macro.
farcalloc function Yes This is the same as calloc.
farcoreleft function Yes This is supposed to determine how much space remains on the heap. There's no way to do this, since the heap size is not limited in any practical sense.  Hence, it is a macro that simply always has the value 512K.
farfree function Yes This is the same as free.
farmalloc function Yes This is the same as malloc.
fcloseall function Linux: Yes
FreeBSD: No
Other: TBD
Requires TurboC.h.  This is not a function for which I provide any code.  It's simply a standard library function.
struct ffblk data type Yes
fillellipse function Yes
fillpoly function Yes
findfirst function Yes While substantially a functional replacement for the Turbo C function of the same name, it is also subtly different in a number of ways:
  • Most importantly, please read about the findlast function.
  • Long filenames (not just 8.3) are supported. 
  • Regular expressions are used for the filename patterns.  This means that expressions like "*.c" and "foobar.?" will work mostly -- but not entirely -- as expected.  For example, the pattern "*" in Linux corresponds more closely to the pattern "*.*" in DOS than does "*.*" in Linux.  (In Linux, "*.*" implies that the filename really contains a dot, and so it wouldn't match a filename like "foobar".)
  • Since *nix filenames are case-sensitive, patterns like "*.c" and "*.C" are not interchangeable.
  • Among the flags, only FA_DIREC corresponds directly to the DOS FA_DIREC  flag. FA_ARCH and FA_LABEL flags are not supported at all.  I've arbitrarily defined FA_RDONLY to correspond to files for which the user-write-permission bit is not set, and FA_SYSTEM to correspond to files for which the user-read-permission bit is not set. FA_HIDDEN is defined to correspond to files whith names beginning in '.'.  However, this does not work on all systems.  (It works in Linux, but not presently in BSD.)
findlast function n/a This is not a function provided by true Turbo C, but is provided to correct a problem in the libTurboC emulation.  The "normal" use of findfirst/findnext, as defined by me, is that the entire file list is read, and then terminates when findnext cannot locate any more files.  If the functions are not used in this way -- in other words, if findnext never locates the last file -- then libTurboC has no way to know that it should free the memory which has been allocated.  With each "abnormal" use of findfirst/findnext this memory will accumulate.  The symptom is that eventuallyfindfirst/findnext will not be able to locate files even though they exist.  This problem can be fixed by explicitly adding a call to findlast after the last use of findnext, but before deallocating its struct ffblk .   The prototype is:
void findlast (struct ffblk *);
findnext function Yes See the notes for findfirst.
floodfill function TBD I may prove to be too darned lazy for this.  However, there's a GRX function that does this.  If anyone wants to adapt it ...
fnkeys.h header file n/a This is a file I've provided, but there is not any equivalent Turbo C header file.  This header simply provides symbolic names for all of the special-function keys recognized by MS-DOS.  Unfortunately, these are not all supported by ncurses.  See the discussion below.
getarccoords function Yes Requires the "-lm" compiler switch.
getaspectratio function Yes There is a function of this name, but at this point it acts as though the pixels are always square.
getbkcolor function Yes
getch function Yes There is an ncurses function of the same name, but somewhat different functionality.  In any source file using conio.h, the conio version of getch applies below the #include "conio.h", while the ncurses version of getch applies above it.  The ncurses functionality continues to be available, however, as a new function getchNcurses .

Please note that getch will work in textmode or in graphics mode, but will not presently work otherwise.  Conversely, getchar will work only when not in textmode .  (getchar will work in graphics mode if textmode has not been previously called, but will not echo to graphics screen).

getche function Yes
getcolor function Yes
getdate function Yes Contributed by Igor Bujna.  In some newer system libraries, there actually is a function called getdate, which works differently and conflicts with this function.  That function, if it exists, will be accessible in TurboC programs as getdateSystem.
getdefaultpalette function Yes The true Turbo C function returns a pointer to a struct palettetype , whereas the TurboC library function returns a pointer to const struct palettetype.
getdrivername function Yes This functions returns a const char *, whereas the true Turbo C function returns char *.
getfillpattern function Yes
getfillsettings function Yes
getftime function Yes I initially believed that this function did not work, because the linker could not find the fstat function on which it is based.  Later, this problem mysteriously disappeared.   I mention this just FYI.
getgraphmode function Yes
getimage function Yes Borland's documentation does not specify the format of the buffer into which the image is placed, beyond fact that the first two words contain the width and height, in pixels.  If you use this function with those restrictions in mind, you'll be okay.

On the other hand ... I think it's very likely that programs containing  this function might exploit knowledge of the graphics controller in the PC, and thus may (improperly if cleverly) directly manipulate date within the output graphics buffer.  Realize that no effort has been made to duplicate these  undocumented buffer formats. If your program depends on the size or format of the graphical area of the output buffer, I guarantee that it will not work!

As a corollary, be sure to allocate image buffers dynamically using imagesize, per Borland's docs, with malloc or calloc.  I suspect that many existing programs statically allocate the buffers, on the incorrect notion that the buffer format is known.

Finally, you should not expect to be able to save the image buffer as a file and to reload it later.

getlinesettings function Yes
getmaxcolor function Yes
getmaxmode function Yes See the comments for getmoderange.
getmaxx function Yes
getmaxy function Yes
getmodename function Yes Since the TurboC library does not limit the graphics modes to those of a particular "graphics driver" as Borland Turbo C does, and since there are many more graphics modes, it is not practical to make the name strings identical to those reported in an actual Turbo C program.
getmoderange function Yes Since the TurboC library rejects the concept of a "graphics driver", every graphics mode is allowed for every driver.  Furthermore, while various graphics modes are available under the same symbolic constant names as in true Turbo C (such as VGAHI, VGALO, etc.), the symbolic constants don't have the same numeric values as in true Turbo C, and many more modes are available than are assigned symbolic constants.  (To understand this, refer to the graph.h file.)  The upshot of all this is that getmoderange returns a huge range of allowable modes, in comparison to true Turbo C.  At this writing, the range is from 0 to approximately 1439, whereas true Turbo C topped out at about 5; this maximum mode presently provides a 1280x1024 screen with 256 colors and 4 pages.  Whether this presents a problem remains to be seen.
getpass function Yes
getpixel function Yes In true Turbo C, we are guaranteed that the on-screen color corresponds to an actual color in our palette.  In the TurboC library, this isn't true.  The closest-match paletted color is returned.  If there is more than one match, the first one encountered is returned.
getpalette function Yes
getpalettesize function Yes
gettext function Yes The format of the text buffer created is the same as in true Turbo C.  The same bytes are produced, and they are stored in the same order.

11/02/03 and later:  There is a function called gettext in the internationalization library (libintl).  To avoid a conflict, the internationalization library's function will be accessible instead by the name gettextIntl.
gettextinfo function Yes
gettextsettings function Yes
gettime function Yes There are two versions of this, one by me, and one by Igor Bujna (called gettime_d).   I'm not aware of the pros and cons of the two.
getviewsettings function Yes
getx function Yes
gety function Yes
gotoxy function Yes
graphics.h header file Yes At present, most graphics.h functionality is supported in one form or another except text output, which is next on the to-do list.

Use of graphics requires the X-window system.

graphdefaults function Yes
grapherrormsg function Yes
_graphfreemem function Yes This function is not used in any way by the TurboC library -- or hopefully, by the user code -- but has nevertheless been provided.
_graphgetmem function Yes See the comments for _graphfreemem.
graphresult function Yes
highvideo function Yes
huge type modifier Yes Requires TurboC.h.  There's no need for "huge pointers" with a 32-bit compiler, so this is simply an empty macro.
imagesize function Yes Important:  see the warnings for the getimage function above.
initgraph function Yes Causes a separate graphics window to open.  (The parent text-based window remains visible.)  The location of this graphics window (i.e., locally or remotely) is dependent on the value of the DISPLAY environment variable.  Typically (but not always) this variable is set automatically for you by the system, and so you usually don't have to worry about it.  The graphdriver and pathtodriver input-parameters of initgraph are (almost) completely ignored, though the constants used as names for the various drivers are available for your use (DETECT, CGA, MCGA, EGA, etc.).  As far as the graphmode input-parameter is concerned, every mode applicable to any graphics driver is accepted.  All graphics modes through Borland C++ 5.0 are supported:  CGAC0, CGAC1, CGAC2, CGAC3, CGAHI, MCGAC0, MCGAC1, MCGAC2, MCGAC3, MCGAMED, MCGAHI, EGALO, EGAHI, EGA64LO, EGA64HI, EGAMONOHI, HERCMONOHI, ATT400C0, ATT400C1, ATT400C2, ATT400C3, ATT400MED, ATT400HI, VGALO, VGAMED, VGAHI, PC3270HI, IBM8514HI, IBM8514LO.
insline function Yes
installuserdriver function Yes (sort of) Graphics drivers as such are not used by the TurboC library (which allows every defined graphics mode to be used by every "driver" anyway).  This function, therefore, does nothing.  It always returns a value of IBM8514.
installuserfont function TBD
io.h header file Yes This is supported in the sense that a file of this name is provided.  However, not all of the functions are necessarily supported.
kbhit function Yes
line function Yes
linerel function Yes
LINES variable n/a This is not present in true Turbo C.  It is an ncurses variable that tells the current number of text rows in the display console.
lineto function Yes
lowvideo function Yes
mkdir function Yes A function of the same name is provided by GNU gcc, but behaves somewhat differently in the Linux environment.  The version provided by TurboC corrects that behavior.
moverel function Yes
movetext function Yes
moveto function Yes
normvideo function Yes
outtext function Yes See the comments for outtextxy.
outtextxy function Yes See the comments for settextstyle

Borland seems to perform clipping on text by not displaying any characters that aren't wholly within the viewport.  The TurboC library performs clipping on text by not displaying any pixels of the characters that are outside of the viewport.  In other words, the TurboC library may display partial characters in some cases, whereas true Turbo C will not do so.

pieslice function Yes
putch function Yes
putimage function Yes Important:  see the warnings for the getimage function above.
putpixel function Yes
puttext function Yes See the notes for gettext
random function Yes Requires TurboC.h.
randomize function Yes Requires TurboC.h.
rectangle function Yes
registerbgidriver function Yes (sort of) This function serves no purpose in the TurboC library, since there is no need to load separate graphics "drivers".  Hence, this function actually does nothing.  It always returns a value of IBM8514, which probably doesn't correspond to what you might have wanted.  Therefore, it is probably best to write this function out of your code.
registerbgifont function TBD
restorecrtmode function Yes Note that Borland's documentation does not specify whether the resulting text-mode screen is cleared or not.  With the TurboC library, it will not be cleared.
sector function Yes Requires the "-lm" compiler switch.
setactivepage function Yes
setallpalette function Yes
setaspectratio function Yes There's a function of this name, but it does nothing, on the assumption that the pixels are always square.
setbkcolor function Yes See the comment for setpalette below.
setcolor function Yes
_setcursortype function Yes This function was not present in Turbo C 2.0, but appeared in some later versions.  The cursor type, as in Turbo C, is one of the following: _NOCURSOR, _NORMALCURSOR, _SOLIDCURSOR.  However, ncurses does not provide these choices as such; it provides only "invisible", "visible", and "very visible", with the differences between these being dependent on the target platform.  For example, on my iMac Linux box, both _NORMALCURSOR and _SOLIDCURSOR appear as indistinguishable block cursors.  In other words, your mileage may vary.
setfillpattern function Yes
setfillstyle function Yes
setftime function No The closest *nix function corresponding to this that I can find is utimes, which unfortunately requires knowing the filename.  On the other hand, setftime requires the handle of an open file.  There's no clean way I know to determine a filename given a file handle.  I don't see any clean way to implement this without intercepting all open and fopen calls.

Workaround:  Rewrite your code to use utimes rather than setftime.

Note:  Actually, there is a way of writing such a function without trapping fopen, but it's so unclean that I'd hesitate to do it.  I'd be happy to receive someone else's code for it, though.  Given the file handle, the fstat function can reveal the file's "inode".  There's no way to do a reverse lookup and determine a filename given an inode, but a search of the entire file-system (using the find function from the command line, with the appropriate switches) can give a list of the filenames of all files with a given inode.  The search can be made relatively efficient by first searching just the current directory, and then searching the home directory only on failure, and then searching the entire file-system only on failure.  (Unfortunately, the inode numbers are not necessarily unique.  They are only unique within a given file-system, and if multiple file-systems are mounted, they could each have files with the same inode.)  Finally, after find has determined the filename, the utimes functions could be used.  Ick!

setgraphbufsize function Yes ... and no Yes there is a function of this name.  No, it doesn't do anything, though it does return the correct values.  I don't allow you to alter the size of any memory buffers used internally by the TurboC library.
setgraphmode function Yes
setlinestyle function Yes
setpalette function Yes In true Turbo C, changes to the palette may instantly be seen on the graphics display, because true hardware modes within the graphics controller are affected.  With the TurboC library, only future drawing operations are affected, but pixels which have already been drawn are unaffected.
setrgbpalette function Yes See the comment for setpalette above.
settextjustify function Yes Borland Turbo C 2.x seemingly has a bug in which if the text style is HORIZ_DIR, then LEFT_TEXT is treated as RIGHT_TEXT .  This bug has not been duplicated in the TurboC library.
settextstyle function Yes ... and no So far (20020608), only the bitmapped font (DEFAULT_FONT) has been implemented. 

Eventually, all stroked fonts defined in Borland C++ 5.0 will be supported, supposing that I can find appropriate open-source fonts with which to implement them:    TRIPLEX_FONT, SMALL_FONT , SANS_SERIF_FONT, GOTHIC_FONT, SCRIPT_FONT, SIMPLEX_FONT, TRIPLEX_SCR_FONT, COMPLEX_FONT, EUROPEAN_FONT, BOLD_FONT

setusercharsize function TBD
setviewport function Yes
setvisualpage function Yes
setwritemode function Yes Supports not only the modes COPY_PUT and XOR_PUT specified by Borland, but also the modes OR_PUT, AND_PUT, and NOT_PUT (which in true Turbo C were used only for the putimage function).
sopen function Yes This function (implemented as a macro) was contributed by Igor Bujna.  Never having used it myself, I don't know how closely it matches the Turbo C function.  However, O_TEXT is defined identically to O_BINARY, so it clearly doesn't distinguish between text and binary modes.
_stklen global variable Yes Requires TurboC.h.  In Turbo C, this was used to define the size of the stack.  This is pointless in gcc, so a variable of this name is provided, but assigning it a value does nothing.
strcmpi function Yes Requires TurboC.h.  This is simply a macro that renames the function as strcasecmp.
stricmp function Yes Requires TurboC.h.  This is simply a macro that renames the function as strcasecmp.
strlwr function Yes Requires TurboC.h.
strncmpi function Yes Requires TurboC.h.   This is simply a macro that renames the function as strncasecmp.
strupr function Yes Requires TurboC.h.
const int TcUnicodeMappings[256] global variable n/a This is a resource not available in true Turbo C, but is helpful if you choose to use Xlib functions rather than graphics.h functions to display text on a graphics-mode screen.  Except for the usual ASCII printable characters (0x20-0x7E), the character set in normal *nix fonts is not the same as the normal character set in MS-DOS.  However, you can fake up this character set if a Unicode font (one with font descriptions ending in 10646-1) is used.   The array simply provides a decent Unicode equivalent for MS-DOS characters.  Every character is represented,  but not every character is necessarily present in every Unicode font.  The so-called GNU Unifont supports every character we reference.  Note that lots of characters were missing from the original Borland-supplied stroked fonts anyhow.
textattr function Yes (See notes for textcolor.)
textbackground function Yes (See notes for textcolor.)
textcolor function Yes For color control, Borland's color constants are used, and are assigned the same numerical values as in Turbo C:  BLACK, BLUE, GREEN, CYAN, RED, MAGENTA, BROWN, LIGHTGRAY, DARKGRAY, LIGHTBLUE, LIGHTGREEN, LIGHTCYAN, LIGHTRED, LIGHTMAGENTA, YELLOW, WHITE, BLINK.  Whether or not you actually get blinking when using BLINK seems to depend on the console being used.  For me, it seems to blink with KDE's konsole but not with xterm.  Anyhow, your mileage may vary.
textheight function Yes
struct text_info data type Yes
textmode function Yes All of the Turbo C 2.0 text modes are supported, and I've included many added later, up to those defined in Borland C++ 5.5.  The same constants, with the same numerical values are used as in Turbo C.  (BW40, C40, BW80, C80, MONO, C4350, ....) 

If you don't explicitly call textmode before beginning to use the various console-i/o operations, there is an implicit call textmode(C80). Unfortunately, even though the initial call to textmode is optional, there is a non-optional call to textmode at the end of the program, not needed by the original Turbo C program but needed by the TurboC library.  A mode called EXITMODE not found in Turbo C is provided to allow ncurses to gracefully shutdown.  You must call textmode(EXITMODE) prior to exiting your program, or else you risk losing control of the console from within which you're running the program.

TurboC does not actually distinguish between B&W and Color modes; all modes are color modes. 

The rationale for sizing of the text console differs somewhat between Turbo C and ncurses, in a way that makes it difficult to reconcile them with perfect accuracy.  You'll want to read the section titled "Screen resizing" for an explanation.

textwidth function Yes
struct time data type Yes
TurboC.h header file n/a There is no Turbo C header file of this name, but this is sort of a catch-all header I've created to cover everything not directly covered in conio.h and the other actual Turbo C header files.  For example, it contains the integer datatype conversion macros and the prototypes for the strupr and strlwr functions (which are handled in Turbo C by the string.h header file, but can't be handled in gcc that way because string.h already exists). This file is automatically included if any of the other header files (conio.h, io.h, dir.h, etc.) are included.
ungetch function Yes There is an ncurses function of the same name, but somewhat different functionality.  In any source file using conio.h, the conio version of ungetch applies below the #include "conio.h", while the ncurses version of ungetch applies above it.  The ncurses functionality continues to be available, however, as a new function ungetchNcurses .
unixtodos functions Yes Contributed by Igor Bujna.
wherex function Yes
wherey function Yes
window function Yes
_wscroll variable Yes This global variable variable was not present in Turbo C 2.0, but is present in some later versions.

Handling of integer datatypes

Since the MS-DOS based Turbo C compiler is 16-bit and GNU gcc is inherently 32-bit, there are some unfortunate discrepancies in the sizes of integer datatypes between them.  This usually doesn't matter, but sometimes does matter -- for example, in disk i/o or where the programmer has counted on certain types of rollover.

The TurboC library allows you to handle this problem in two separate ways, at your option.  The first way, of course, is simply to ignore the problem and to assume that an int is an int is an int.  :-)   In other words, datatypes can be left unchanged, and it's up to you to figure it out later, if your program doesn't work.  By default, though, TurboC redefines the words short, int , unsigned, and long using macros so that they are replaced by GNU datatypes specifically corresponding to the Turbo C datatypes, namely:

#define short int16_t
#define int int16_t
#define unsigned uint16_t
#define long int32_t
(You may wonder why there's a macro for long, since it's a 32-bit datatype on both Turbo C and gcc.  If so, you've fallen into the Turbo-thinking trap!  The long datatype is 64-bit for some CPU types supported by gcc.)

This scheme has the advantage of transparently fixing almost all data declarations in your program.  Those declarations which are not fixed properly, such as unsigned long or the use of unsigned to define bitfields in a struct, are broken.  This is actually good news, because the compiler gives you an error message and you're allowed to fix the problem, rather than just allowing you to assume everything is swell.  The resources you have to fix the problems with are the various explicit datatypes provided by GNU gcc (int8_t,uint8_t, int16_t, uint16_t, int32_t, and uint32_t) and some new datatypes defined by the TurboC library corresponding to the original (non-macro-replaced) GNU datatypes: gchar, gschar , guchar, gshort, gushort, gint, guint, glong, and gulong.

For example, after automatic macro conversion, things like the following will be correct

int i, j, k;
unsigned u;
char c;
short is;
long n;
but things like this will be wrong:
unsigned int i, j, k; // Change to unsigned or to uint16_t.
unsigned char c; // Change to uint8_t.
struct MyStruct
  int i; // Okay.
  unsigned x:1; // change to guint.
  unsigned y:2; // change to guint.
int main (int argc, char *argv[]) // Change to gint.
The automatic conversions are enabled by default, but can be disabled with the "-DDoNotFixIntegers" compiler switch.  You have to decide for yourself which is more appropriate.  Enabling the automatic conversions means that your program is more likely to work correctly once ported.  But it also means that it may be more difficult to maintain afterward because it will be filled with things that look like int but aren't really.

Note that if you want to use "-DDoNotFixIntegers" to compile the code you're porting, a different version of the library is used -- libTurboCu.a rather than libTurboC.a.  Both library versions are automatically built, for versions 20020319 or later.  (For earlier versions, I'm afraid you'll have to build libTurboCu.a yourself by manually changing the Makefile to have the gcc switch -DDoNotFixIntegers).

Here is a tabular summary of how the integer datatype declarations are handled if converted automatically by the TurboC library:

Turbo C type Size Equivalent
GNU gcc type
Handling by TurboC
char 8 char Correct
signed char 8 signed char Correct
unsigned char 8 uint8_t Causes compile-time error.  Replace manually with uint8_t .
short 16 int16_t Correct
unsigned short 16 uint16_t Causes compile-time error.  Replace manually with uint16_t .
short int 16 int16_t Causes compile-time error.  Replace manually with short .
unsigned short int 16 uint16_t Causes compile-time error.  Replace manually with uint16_t .
int 16 int16_t Correct
int bitfields in structs varies int Causes a compile-time error.  Replace manually with gint .
unsigned int 16 uint16_t Causes compile-time error.  Replace manually with unsigned .
unsigned 16 uint16_t Correct
unsigned bitfields in structs varies unsigned Causes a compile-time error.  Replace manually with guint .
long 32 int32_t Correct
unsigned long 32 uint32_t Causes compile-time error.  Replace manually with uint32_t .
long int 32 int32_t Causes compile-time error.  Replace manually with long .
unsigned long int 32 uint32_t Causes compile-time error.  Replace manually with uint32_t .

Special-function keys

In Turbo C, special keyboard character such as F1 or Ctrl-PgUp are indicated by a two-byte sequence with the getch function:   If the first byte returned is 0, then the next byte indicates which special-function key has been pressed.  The values for this second byte have been summarized in the fnkeys.h file, which also provides symbolic names for all of them.

Unfortunately, many function-key sequences available using getch in MS-DOS are not available at all using the ncurses library.  (For example, F1 is available, but Ctrl-PgUp is not.)  Others may or may not be available, depending on various factors.   Consequently, while the TurboC library has mimicked this functionality as best it can -- or rather, as best I can -- you may still be in the position of having to change some of the special-function keys used by your program.

Here's a list of all special keys that I believe are handled by Turbo C's getch function, along with my observations of how they are handled by the TurboC library's getch function.  Your mileage may vary.

Special Key Symbol provided in fnkeys.h Under xterm Under KDE Konsole Under a text-mode login
Digits on numeric keypad n/a (0-9, of course) Ok Ok No!  Treated as arrows, PgUp/PgDn.
Ctrl-A through Ctrl-Z C_A-C_Z Ok Ok Ok, except there is no Ctrl-Z.
Alt-A through Alt-Z A_A-A_Z Ok Ok, except that Alt-O has a slight delay before registering. Ok
F1 through F10 N_F1-N-F10 Ok Ok Ok
Shift-F1 though Shift-F10 S_F1-S_F10 Ok, except Shift-F5 terminates program Ok, except:  Shift-F5 terminates program, and F9-F10 don't work. Ok, except:  Shift-F5 terminates program, and F9-F10 don't work.
Alt-F1 through Alt-F10 A_F1-A_F10 No!  (These are KDE hotkeys.) No!  (These are KDE hotkeys.) No!  (Switches between consoles.)
Ctrl-F1 through Ctrl-F10 C_F1-C_F10 No!  (These are KDE hotkeys.) No!  (These are KDE hotkeys.) No!
Alt-0 through Alt-9 A_0-A9 Ok Ok Ok
Arrows N_UP, N_DOWN, N_LEFT, N_RIGHT Ok Ok on standalone arrow keys, but not on numeric keypad. Ok
PgUp, PgDn N_PGUP, N_PGDN Ok Ok on standalone arrow keys, but not on numeric keypad. Ok
Home, End N_HOME, N_END No! Ok on standalone arrow keys, but not on numeric keypad. No!
Ins, Del N_INS, N_DEL Ok Ok on standalone arrow keys, but not on numeric keypad. Ok
Pad-minus, Pad-plus N_PADPLUS, N_PADMINUS Ok No, treated as regular +/-. No, treated as regular +/-.
Ctrl-right, Ctrl-left C_LEFT, C_RIGHT Ok on standalone arrow keys, but not on numeric keypad. No, treated as regular right/left. No, treated as regular right/left.
Ctrl-PgUp, Ctrl-PgDn C_PGUP, C_PGDN No! No, treated as regular PgUp/PgDn. No, treated as regular PgUp/PgDn.
Ctrl-Home, Ctrl-End C_HOME, C_END Ok on standalone arrow keys, but not on numeric keypad. No, treated as regular home/end. No!
Alt-minus, Alt-equals A_MINUS, A_EQUALS Ok Ok Ok on main keyboard, but not on the numeric keypad.
Esc N_ESC Ok, though there is a short delay before the keystroke registers. Ok, though there is a short delay before the keystroke registers. Ok, though there is a short delay before the keystroke registers.

I'd be happy to hear from anyone with a clear idea on how make this work more consistently, perhaps by using termcap/terminfo, of which I'm completely ignorant.

Text Screen resizing

In true Turbo C, the resolution of the text console is completely under the control of the programmer.  The textmode function sets the resolution, in terms of the number of text rows and columns, and sets the graphics modes appropriately.  If a Turbo C program is run under Microsoft Windows, the same situation applies, in essence, because even though Windows renders the text console by means of graphical operations, the number of text rows and columns is fixed, and cannot be changed by the user.

The situation is different in ncurses -- at least, if using the X-Window system -- because the size of the text console is entirely under the control of the user.  The user can resize the text console at will, and the program has little effective control over the resizing.

This presents a difficulty, because Turbo C programs have naturally been written under the suppositions that the text console size has been set by the program itself, and that the text console is not going to be unexpectedly resized during program execution.  Yet, these suppositions are both rather dodgy with code that has been ported using the TurboC library.

There are several possible approaches to the problem:

  1. For TurboC versions 04/18/02 and later, the screen size is now correct if the ported program is run under xterm.  TurboC physically resizes the xterm console correctly upon starting the program.  While it cannot prevent the user from manually resizing the window later, it will correct any manual resizing by automatically restoring the window to its correct size.  (Sadly, it is possible for a persistent user to corrupt the window by trying hard enough to resize it, but the behavior is usually pretty acceptable.)  Or,
  2. If for some reason it's impractical to use xterm, or if the window manager being used resists TurboC's attempts to resize xterm , then you may need to use some method outside of TurboC (such as instructions to the user) to prevent resizing of the window; or
  3. Set the BypassResizeXterm variable to 1, and recode those portions of your program that depend on knowledge of the screen size (such as those using gotoxy and window functions) so that they are more flexible.   For example, don't use things like gotoxy(1,25) , but use gotoxy(1,LINES) instead.
In implementing approach #3, several tools are at your disposal. Firstly, the variables LINES and COLS are available for your use.  These variables always contain the number of text rows and text columns, respectively, in the text console.  Secondly, the TurboC library can detect (in versions 20020331 and later) if the user has resized the console.   When it detects that such resizing has occurred, it calls a function called ConioResizeCallback.  You can optionally provide this function yourself (though the TurboC library provides a default version of the function which does nothing), and can use this function in a variety of ways to take care of the screen resizing.  Perhaps the most straightforward way to do so is to simply allow ConioResizeCallback to completely redraw the screen.

In the latter case, by the way, if the user manually resizes the text console, then your current window (as determined by the windowor textmode function) will automatically be reduced in size (if necessary) to fit the new console size.  However, it will not be correspondingly increased in size of the user later enlarges the text console.  To override this behavior, you'll need to provide an alternative to the ResizeTurboC function.   You'll need to examine the source code for any further explanation.

Graphical display characters in text mode

When using functions such as printf, putchar, etc., no attempt is made to translate displayed characters so that they appear identical to those on an IBM PC.  In other words, you're just using the native *nix functions, and you get whatever you get.  Typically, you should expect only the characters in the numerical range 0x20-0x7E to display accurately.  However, when using the various conio.h functions, such as cprintf , putch, etc., we attempt to match the output characters as closely as possible to those in true Turbo C on an IBM PC.

When I say that we attempt to map the characters as closely as possible, I mean that given a character with a certain numerical code, we attempt to display a character that looks as much as possible like the IBM PC character with that same numerical code.  On the other hand, we have no way to translate string characters appearing in your source code.  What do I mean by this?  Well, consider the character 'é'.  This happens to correspond to character 0x82 in the IBM PC character set.  Suppose you have source code like this:

putch ('é');     /* bad! */
putch (0x82);    /* good! */

What makes the first of these two lines "bad" is that the numerical code which the compiler creates for 'é' is based on the character sets and languages installed on the computer doing the compiling, and is very likely not 0x82.  So the first form is almost guaranteed not to work properly.  Even so, calling the second form "good" is stretching a point, because (as it happens), the TurboC library isn't presently able to display the character 'é' anyway.  True Turbo C is able to display any of the characters in the IBM PC character set -- i.e. the standard printable 7-bit ASCII characters, plus additional characters in the numerical ranges 0-31 and 128-255.  However, the TurboC library does not fully support this capability in text mode, because the ncurses library does not.  A subset of the IBM PC character set is supported, including linedraw characters.  (However, all linedraw characters representing double-lines or combinations of double/single lines are represented simply in terms of single lines.)

Screenshots of displayable Characters
True Turbo C display characters -- click to enlarge.
True Turbo C
TurboC library display characters -- click to enlarge.
TurboC library

(Click here to see the program that generated this output.)  As you may notice, non-supported characters are rendered as dots.  Actually, this can be changed within the ported program to any other character as follows:

  Add this code prior to the FIRST use of any conio function.
  The default character cannot be changed after initialization.
  The values used are any integer character code recognized by
  ncurses (NOT IBM PC character codes).
extern gint DefaultChar;
DefaultChar = ' ';              /* or whatever */
If this still isn't good enough for you, you can individually control the mapping of every character.  For example:
  Add this code AFTER the first use of textmode.
  It will be overridden if placed BEFORE textmode.
extern gint TranslatedChar[256];
TranslatedChar[0x9d] = 'Y';     /* support YEN as 'Y'. */

Graphics mode

Note:  The material in this section and the next describes both features that exist and features that are planned for the future.  Consult the change log for more info about the support provided in specific code versions.

In true Turbo C, graphics-mode screens (as opposed to text-mode screens) are handled by something called the Borland Graphics Interface, or BGI for short.  The BGI is an API containing 80+ functions.  Note that the graphics functions provided with the TurboC library are somewhat less portable than the remainder of the library, in that the X-window system is required.  If you need graphics functions that can operate without X, I'd suggest reading the next section.

Some of the more important points of departure from true Turbo C are these:

Alternative graphics-mode functions

If the graphics-mode discrepancies described above are too awful for you to live with, it is possible in theory to disable the TurboC-provided graphics functions and instead to use alternate functions.  (I've not actually tried any of this myself, so if you make it work I'd appreciate it if you could send me detailed instructions.)

For example, there is a 2D graphics library called the GRX library ( by Csaba Biegl, Michael Goffioul, and Hartmut Schirmer).  The GRX website does not advertise (or even mention) Turbo C compatibility. However, it contains quite a few functions of the same name (and, apparently, the same functionality) as Turbo C library functions.   To find out more, download the library using the link above.  After unpacking the tarball, you'll find the Borland replacement functions in the src/bgi directory, and information about them in the doc/readme.bgi file.

Disabling the graphics functions present in the TurboC library involves these steps:

  1. Edit the TurboC library's Makefile, remove the compiler switch "-DWITH_X", and rebuild the TurboC library.
  2. Eliminate the TurboC version of graphics.h from the system includes (probably /usr/include).
  3. Install GRX.
Realize that I have not really evaluated the GRX library, and so do not understand its ins and outs.  For example, I don't know how many BGI functions it implements.  I believe that the main advantage of GRX relative to TurboC is that in a system without X it can directly used the graphics controller. I believe that the main disadvantage of GRX relative to TurboC is that it is not integrated with the other non-graphics Turbo C functions like getch.  Since the TurboC library's version of getch (for example) depends on the TurboC library's implementation of graphics functionality, it will not work properly with GRX.

Endian conversions

Since all Turbo C functions have been run only on Intel 'x86 processors, it is not uncommon in Turbo C code to find that the programmer has simply assumed that the CPU is little-endian -- i.e., that the LSB of multi-byte integers precedes the MSB.  In porting such code to GNU gcc, one has to recognize that it may not necessarily be run on a little-endian processor.  For example, I do a lot of work on an iMac, which is based on a big-endian PowerPC processor.  This is not important in most cases, but does affect various operations such as the matching of bytes within union objects and, especially, reading/writing files.

To make it easier to deal with this problem, I've provided a number of functions not originally present in Turbo C that can be used to convert endian types where required.  Unfortunately, it's still up to you to figure out that there's a problem and to add these function calls to the program.

There are two separate groups of functions, those which convert the endian type of an integer value already stored in memory, and those which convert data on-the-fly whilst reading/writing a file.  All of the functions require the TurboC.h header file.

Function prototype Description
void FixLittle16 (uint16_t *); Performs an in-place conversion of a 16-bit integer value stored in memory from little-endian format to the natural CPU endian format, or vice-versa .  Using this function twice in succession gets back whatever you started with.  There's no harm using this function if the CPU happens to be little-endian, since the value is passed through unchanged in that case.
void FixLittle32 (uint32_t *); Same as FixLittle16, but 32-bit instead.
void FixBig16 (uint16_t *); Same as FixLittle16, but big-endian instead.
void FixBig32 (uint32_t *); Same as FixLittle16, but 32-bit big-endian instead.
int ReadLittle16 (FILE *fp, uint16_t *Value); Reads a 16-bit little-endian integer from a file, and delivers it in the natural endian-format of the CPU.  Returns 0 on success, non-zero on failure.
int ReadBig16 (FILE *fp, uint16_t *Value); Same as ReadLittle16, but big-endian instead.
int ReadLittle32 (FILE *fp, uint32_t *Value); Same as ReadLittle16, but 32-bit instead.
int ReadBig32 (FILE *fp, uint32_t *Value); Same as ReadLittle16, but 32-bit big-endian instead.
int WriteLittle16 (FILE *fp, uint16_t Value); Takes a 16-bit integer value in the natural endian format of the CPU, and writes it to a file as a 16-bit little-endian integer.  Returns 0 on success and non-zero on failure.
int WriteBig16 (FILE *fp, uint16_t Value); Same as WriteLittle16, but big-endian instead.
int WriteLittle32 (FILE *fp, uint32_t Value); Same as WriteLittle16, but 32-bit instead.
int WriteBig32 (FILE *fp, uint32_t Value); Same as WriteLittle16, but 32-bit big-endian instead.


Hello, world!  Consider the following Turbo C program:
#include <conio.h>
#include <time.h>

main (void)
  time_t t, newt;
  int i = 0, x, y;
  time (&t);
  clrscr ();
  cprintf ("Hit any key to continue: ");
  x = wherex ();
  y = wherey ();
  // Wait for a keypress, flashing the message
  // "I'm waiting!" on and off once per second.
  // After any key is hit, display "Hello, world!"
  while (!kbhit ())
      time (&newt);
      if (t != newt)
          t = newt;
          if (0 == (i & 1))
            cprintf ("I\'m waiting!");
          clreol ();
          gotoxy (x, y);
  getch ();
  cprintf ("\r\nHello, world!\r\n");

This program almost compiles with GNU gcc (and the TurboC library), and almost works as-is,  except for a couple of points: Having done these things, you'll find that you can compile the program and run it without any errors:
gcc -o Hello Hello.c -lTurboC -lncurses
xterm +sb -e Hello
Compiling without warnings is actually a little unusual, because there are quite a few things that can cause non-fatal warning messages.  See the trouble-shooting section for more detail.


Well, as you've seen, there are many factors that come into play porting from Turbo C to gcc/TurboC.  Some of these are describe above, but there are others that haven't even been hinted at.  For the sake of completeness, here's a somewhat-complete list of the difficulties I've personally encountered:

Summary or illumination of trouble-shooting items covered earlier

Trouble-shooting items not covered earlier

©2002,2004 Ronald S. Burkey.  Last updated 02/14/04 by RSB.  Contact me.