C Programming Topics

These topics contain information about general C programming and a comprehensive library reference for C functions.

General C programming topics include complex declarations, escape sequences, operators, register structures for assembly code interface and variable arguments.

If using Microsoft C compiler, it can be useful to check the MSC compiler fatal errors and MSC CLI options (v6.0) topic.

C Functions Reference

Assembly ∙ MS-DOS ∙ BIOS ∙ Standard I/O ∙ Console I/O ∙ Other I/O ∙ Filesystem ∙ Allocation ∙ Graphics ∙ Standard library ∙ Process/IPC ∙ Time and date ∙ String and memory ∙ Math ∙ Assertions ∙ Type

Assembly Language Interface

• void _chain_intr( void (interrupt far *target)() )
• unsigned int _clear87( void )
• unsigned _control87( unsigned new, unsigned mask )
• void _disable( void )
• void disable( void )
• void _enable( void )
• void enable( void )
• unsigned FP_OFF( void far *fptr )
• unsigned FP_SEG( void far *fptr )
• void _fpreset( void )
• void geninterrupt( int interrupt_num )
• void _harderr( void (far *handler)() )
• void _hardresume( int result )
• void _hardretn( int error )
• void harderr( int (*fptr)())
• void hardresume( int rescode )
• void hardretn( int errcode )
• int inp( unsigned port )
• int inport( int port )
• unsigned char inportb( int port )
• unsigned inpw( unsigned port )
• int int86( int intr_num, union REGS *inregs, union REGS *outregs )
• int int86x( int intr_num, union REGS *inregs, union REGS *outregs, struct SREGS *segregs )
• void intr( int intr_num, struct REGPACK *preg )
• void longjmp( jmp_buf env, int id )
• void far *MK_FP( unsigned segment, unsigned offset )
• int outp( unsigned port, int datab )
• void outport( int port, int word )
• void outportb( int port, unsigned char byte )
• void outpw( unsigned port, unsigned dataw )
• int peek( unsigned seg, unsigned off )
• char peekb( unsigned seg, unsigned off )
• void poke( unsigned seg, unsigned off, int value )
• void pokeb( unsigned seg, unsigned off, char value )
• void segread( struct SREGS *segregs )
• int setjmp( jmp_buf env )
• unsigned int _status87( void )

MS-DOS Dispatcher Handlers and Utilities

• int allocmem( unsigned size, unsigned *seg )
• int bdosptr( int dosfun, void *argument, unsigned dosal )
• struct country *country(int cntrycode,struct country *cntryp)
• void ctrlbrk( int (*fptr )(void) )
• unsigned _dos_allocmem( unsigned size, unsigned *seg )
• unsigned _dos_close( int handle )
• unsigned _dos_creat(char *fname,unsigned attr,int *handle)
• unsigned _dos_creatnew(char *fname,unsigned attr,int *handle)
• unsigned _dos_findfirst( char *path, unsigned attr, struct find_t *fileinfo )
• unsigned _dos_findnext( struct find_t *fileinfo )
• unsigned _dos_freemem( unsigned seg )
• void _dos_getdate( struct dosdate_t *date )
• unsigned _dos_getdiskfree(unsigned drv,struct diskfree_t *spc)
• void _dos_getdrive( unsigned *drive )
• unsigned _dos_getfileattr( char *path, unsigned *attr )
• unsigned _dos_getftime(int h,unsigned *date,unsigned *time)
• void _dos_gettime( struct dostime_t *time )
• void (interrupt far *_dos_getvect( unsigned intnum ))()
• void _dos_keep( unsigned rc, unsigned size )
• unsigned _dos_open( char *fname, unsigned mode, int *handle )
• unsigned _dos_read( int handle, void far *buffer, unsigned count, unsigned *nread )
• unsigned _dos_setblock( unsigned size, unsigned seg, unsigned *maxsize )
• unsigned _dos_setdate( struct dosdate_t *date )
• void _dos_setdrive( unsigned drive, unsigned *count )
• unsigned _dos_setfileattr( char *path, unsigned attr )
• unsigned _dos_setftime(int handle,unsigned date,unsigned time)
• unsigned _dos_settime( struct dostime_t *time )
• void _dos_setvect( unsigned intnum, void (interrupt far *handler)() )
• unsigned _dos_write( int handle, void far *buffer, unsigned count, unsigned *nbytes )
• int dosexterr( struct DOSERR *errinfo )
• int dosexterr( struct DOSERROR *errinfo )
• long dostounix( struct date *dateptr, struct time *timeptr )
• FILE *fdopen( int handle, char *type )
• int findfirst( const char *path, struct ffblk *ffblk, int attr)
• int findnext( struct ffblk *ffblk )
• int freemem( unsigned seg )
• int getcbrk( void )
• void getdate( struct date *dateblk )
• void getdfree( unsigned char drive, struct dfree *dfreep )
• int getdisk( void )
• char far *getdta( void )
• void getfat( unsigned char drive, struct fatinfo *fatblkp )
• void getfatd( struct fatinfo *fatblkp )
• int getftime( int handle, struct ftime *ftimep )
• unsigned getpsp( void )
• void gettime( struct time *timep )
• void interrupt (*getvect( int intr_num ))()
• int getverify( void )
• int intdos(union REGS *inregs, union REGS *outregs )
• int intdosx( union REGS *inregs, union REGS *outregs, struct SREGS *segregs )
• void keep( unsigned char status, int size )
• char *parsfnm( const char *cmdline, struct fcb *fcbptr, int option)
• int randbrd( struct fcb *fcbptr, int reccnt )
• int randbrw( struct fcb *fcbptr, int reccnt )
• int setblock( unsigned seg, unsigned newsize )
• int setcbrk( int value )
• void setdate( struct date *dateblk )
• void setdta( char far *dta )
• int setftime( int handle, struct ftime *ftimep )
• void settime( struct time *timep )
• void setvect( int intr_num, void interrupt(*isr)() )
• int setverify( int value )
• void sleep( unsigned seconds )
• void unixtodos( long utime, struct date *dateptr, struct time *timeptr)
• int unlink( const char *filename )

BIOS Handlers

• int bdos( int dosfun, unsigned dosdx, unsigned dosal )
• int bioscom( int cmd, char byte, int port )
• int biosdisk( int cmd, int drive, int head, int track, int sector, int nsects, void *buffer )
• unsigned _bios_disk(unsigned cmd,struct diskinfo_t *dskinfo)
• int biosequip( void )
• unsigned _bios_equiplist( void )
• int bioskey( int cmd )
• int biosmemory( void )
• int biosprint( int cmd, int byte, int port )
• int biostime( int cmd, long newtime )
• int _bios_keybrd( int cmd )
• unsigned _bios_memsize( void )
• unsigned _bios_printer(unsigned cmd,unsigned port,unsigned data)
• unsigned _bios_serialcom(unsigned cmd,unsigned port,unsigned fmt)
• unsigned _bios_timeofday( unsigned cmd, long *timeval )

Standard Input/Output (stdio.h)

• void clearerr( FILE *stream )
• int fclose( FILE *fp )
• int fcloseall( void )
• int feof( FILE *stream )
• int ferror( FILE *stream )
• int fflush( FILE *fp )
• int fgetc( FILE *fp )
• int fgetchar( void )
• char *fgets( char *s, int size, FILE *fp )
• int fileno( FILE *stream )
• int flushall( void )
• FILE *fopen( const char *filename, const char *type )
• int fprintf( FILE *fp, const char *format [, arg1, arg2, ...] )
• int fputc( int c, FILE *fp )
• int fputs( const char *s, FILE *fp )
• size_t fread( void *buf, size_t size, size_t count, FILE *fp )
• FILE *freopen( const char *fname, const char *type, FILE *fp )
• int fscanf( FILE *fp, const char *format, arg1, arg2, ... )
• int fseek( FILE *fp, long offset, int mode )
• long ftell( FILE *fp )
• size_t fwrite(const void *buf, size_t size, size_t count, FILE *fp)
• int getc( FILE *fp )
• int getchar( void )
• char *gets( char *s )
• int getw( FILE *fp )
• void perror( const char *string )
• int printf( const char *format [, arg1, arg2, ...] )
• int putc( int c, FILE *fp )
• int putchar( char c )
• int puts( const char *string )
• int putw( int n, FILE *fp )
• int remove( char *filename )
• int rename( const char *oldf, const char *newf )
• void rewind( FILE *fp )
• int rmtmp( void )
• int scanf( const char *format, arg1, arg2, ... )
• void setbuf( FILE *stream, char *buf )
• int setvbuf( FILE *stream, char *buf, int type, size_t size )
• int sprintf( char *s, const char *format [, arg1, arg2, ...] )
• int sscanf( const char *s, const char *format, arg1, arg2, ... )
• char *tempnam( char *dir, char *prefix )
• int ungetc( int c, FILE *fp )
• int vfprintf( FILE *stream, const char *format, va_list param )
• int vfscanf( FILE *stream, const char *format, va_list argp )
• int vprintf( const char *format, va_list param )
• int vscanf( const char *format, va_list argp )
• int vsprintf( char *string, const char *format, va_list param )
• int vsscanf( const char *string, const char *format, va_list argp )

Console Input/Output (conio.h)

• char *cgets( char *s )
• int cprintf( char *format [, argument,...] )
• void cputs( char *s )
• int cscanf( const char *format [,argument,...] )
• int getch( void )
• int getche( void )
• char *getpass( const char *prompt )
• int kbhit( void )
• int putch( int ch )
• void ungetch( int c )

Other Input/Output

• int absread( int drive, int count, int start, void *buffer )
• int abswrite( int drive, int sectors, int start, void *buffer )
• int access( const char *filename, int amode )
• int _creat( const char *fname, int attr )
• int creattemp( char *filename, int attr )
• int _chmod( const char *filename, int func [,int attrib] )
• int chmod( const char *filename, int permiss)
• int _close( int fh )
• int close( int fh )
• int creat( const char *filename, int permis )
• int creatnew( const char *fname, int attr )
• unsigned creatnew( const char *fname, unsigned attr, int fh )
• int dup( int handle )
• int dup2( int oldhandle, int newhandle )
• int eof( int handle )
• long filelength( int handle )
• int ioctl( int handle, int cmd [, void *argdx, int argcx] )
• int isatty( int handle )
• int lock( int handle, long offset, long length )
• int locking( int handle, int mode, long nbytes )
• long lseek( int handle, long offset, int mode )
• int _open( const char *path, int access )
• int open( const char *path, int access [, unsigned permis] )
• int _read( int handle, void *buf, int size )
• int read( int handle, char *buf, int size )
• int setmode( int handle, int mode )
• int sopen( const char *path, int access, int shflag, int mode )
• long tell( int handle )
• int umask( int permission )
• int unlock( int handle, long offset, long length )
• int _write( int handle, char *buf, int count )
• int write( int handle, char *buf, int count )

Filesystem operation

• int chdir( const char *path )
• void fnmerge( char *path, const char *drive, const char *dir, const char *name, const char *ext)
• void fnsplit( const char *path, char *drive, char *dir, char *name, char *ext)
• int fstat( int handle, struct stat *buff )
• int getcurdir( int drive, char *direc )
• char *getcwd( char *buf, int n )
• int mkdir( const char *pathname )
• char *mktemp( char *template )
• int rmdir( const char *path )
• char *searchpath( const char *filename )
• int setdisk( int drive )
• int stat( char *pathname, struct stat *buff )

Memory allocation

• void *alloca( size_t size )
• void _based(void) *_bexpand( _segment seg, void _based(void) *block, size_t size )
• void _bfree( _segment seg, void _based(void) *block )
• int _bheapchk( _segment seg )
• int _bheapset( _segment seg, unsigned fill )
• int _bheapwalk( _segment seg, struct _heapinfo *entry )
• void _based(void) *_bmalloc( _segment seg, size_t size )
• size_t _bmsize( _segment seg, void _based( void ) *block )
• int brk( void *endds )
• unsigned coreleft( void )
• unsigned long coreleft( void )
• void *_expand( void *block, size_t size )
• void far *farcalloc( unsigned long nunits, unsigned long units )
• unsigned long farcoreleft( void )
• void farfree( void far *block )
• void far *farrealloc( void far *block, unsigned long newsize )
• void far *_fexpand( void far *block, size_t size )
• int _fheapchk( void )
• int _fheapset( unsigned fill )
• int _fheapwalk( struct _heapinfo *entry )
• void far *_fmalloc( size_t size )
• size_t _fmsize( void far *block )
• void _ffree( void far *block )
• void free( void *pseg )
• unsigned _freect( size_t size )
• void huge *halloc( long num, size_t size )
• int _heapchk( void )
• int _heapset( unsigned fill )
• int _heapwalk( struct _heapinfo *entry )
• void hfree( void huge *block )
• size_t _memavl( void )
• size_t _msize( void *block )
• void near *_nexpand( void near *block, size_t size )
• void _nfree( void near *block )
• int _nheapchk( void )
• int _nheapset( unsigned fill )
• int _nheapwalk( struct _heapinfo *entry )
• void near *_nmalloc( size_t size )
• size_t _nmsize( void far *block )
• void *sbrk( int incr )
• size_t stackavail( void )

Graphics mode functions

• void far _clearscreen( short target )
• short far _displaycursor( short flag )
• short _ellipse( short ctl, short x1, short y1, short x2, short y2 )
• short _ellipse_w( short ctl, double wx1, double wy1, double wx2, double wy2 )
• short far _ellipse_wxy( short ctl, struct _wxycoord far *pwxy1, struct _wxycoord far *pwxy2 )
• short far _floodfill( short x, short y, short bcolor )
• short far _floodfill_w( double wx, double wy, short bcolor )
• short far _getcolor( void )
• flagType GetColor( LINE line, la *colorlist, PFILE pFile )
• struct xycoord far _getcurrentposition( void )
• struct _wxycoord far _getcurrentposition_w( void )
• unsigned char far *_getfillmask( unsigned char far *mask )
• void far _getimage( short x1, short y1, short x2, short y2, char huge *image )
• void far _getimage_w( double wx1, double wy1, double wx2, double wy2, char huge *image )
• void far _getimage_wxy( struct _wxycoord far *pwxy1, struct _wxycoord far *pwxy2,char huge *image )
• void far getimage( int left, int top, int right, int bottom, void far *bitmap )
• unsigned short far_getlinestyle( void )
• struct xycoord far _getlogcoord( short x, short y )
• struct xycoord far _getphyscoord( short x, short y )
• short far _getpixel( short x, short y )
• short far _getpixel_w( double wx, double wy )
• short far _gettextcolor( void )
• struct rccoord far _gettextposition( void )
• struct videoconfig far *_getvideoconfig( struct videoconfig far *config )
• unsigned far imagesize( int left, int top, int right, int bottom )
• short far _lineto( short x, short y )
• short far _lineto_w( double wx, double wy )
• struct xycoord far _moveto( short x, short y )
• struct _wxycoord far _moveto_w( double wx, double wy )
• void far_outtext( unsigned char far *text )
• short _pie( short control, short x1, short y1, short x2, short y2, short x3, short y3, short x4, short y4 )
• short far _pie_wxy( short ctl, struct _wxycoord far *pwxy1, struct _wxycoord far *pwxy2, struct _wxycoord far *pwxy3, struct _wxycoord far *pwxy4 )
• void PutColor( LINE line, la *colorlist, PFILE pFile )
• void _putimage( short x, short y, char huge *image, short action )
• void far _putimage_w( double wx, double wy, char huge *image, short action )
• void far putimage( int left, int top, void far *bitmap, int option )
• short _rectangle( short ctl, short x1, short y1, short x2, short y2 )
• short far _rectangle_w( short control, double wx1, double wy1, double wx2, double wy2 )
• short far _rectangle_wxy( short control, struct _wxycoord far *pwxy1, struct _wxycoord far *pwxy2 )
• short far _remapallpalette( long far *colors )
• long far _remappalette( short pixnum, long color )
• short far _selectpalette( short palette )
• short far _setactivepage( short page )
• long far _setbkcolor( long color )
• void far _setcliprgn( short x1, short y1, short x2, short y2 )
• short far _setcolor( short color )
• void far _setfillmask( unsigned char far *mask )
• short far _setfont( unsigned char far *options )
• void far _setlinestyle( unsigned short mask )
• struct xycoord far _setlogorg( short x, short y )
• short far _setpixel( short x, short y )
• short far _setpixel_w( double wx, double wy )
• short far _settextcolor( short color )
• struct rccoord far _settextposition( short row, short column )
• void far _settextwindow( short r1, short c1, short r2, short c2 )
• short far _setvideomode( short mode )
• void far _setviewport( short x1, short y1, short x2, short y2 )
• short far _setvisualpage( short page )
• short far _wrapon( short wrap )

Standard library (stdlib.h)

• void abort( void )
• int abs( int n )
• int atexit( void func )
• double atof( const char *s )
• int atoi( const char *s )
• long atol( const char *s )
• void *bsearch( void *key, void *base, int nelem, int width, int (*fcmp )())
• void *calloc( unsigned count, unsigned sizeeach )
• struct _div_t div( int numer, int denom )
• struct _ldiv_t ldiv( long int numer, long int denom )
• char *ecvt( double value, int ndigit, int *decpt, int *sign )
• void exit( int completioncode )
• char *fcvt( double value, int ndigit, int *decpt, int *sign )
• char *gcvt( double value, int ndigit, char *buf )
• char *getenv( const char *envvar )
• char *itoa( int value, char *string, int radix )
• long labs( long n )
• void *malloc( unsigned size )
• void _makepath( char *path, char *drive, char *dir, char *fname, char *ext )
• void *lfind(void *key,void *base,int *nelem,int width,int (*fcmp)())
• unsigned long _lrotl( unsigned long value, int n )
• unsigned long _lrotr( unsigned long value, int n )
• void *lsearch(void *key,void *base,int *nelem,int width,int (*fcmp)())
• char *ltoa( long value, char *string, int radix )
• onexit_t onexit( onexit_t func )
• int putenv( const char *envvar )
• void qsort( void *array, size_t n_elem, size_t elem_size, int (*fcmp)(const void *, const void *) )
• int rand( void )
• void *realloc( void *pseg, unsigned size )
• unsigned _rotl( unsigned value, int shift )
• unsigned _rotr( unsigned value, int shift )
• void _searchenv( char *fname, char *var, char *path )
• void _splitpath( char *path, char *drive, char *dir, char *fname, char *ext )
• void srand( unsigned seed )
• char *ultoa( unsigned long value, char *string, int radix )

Process management and IPC

• int execl( char *pathname, char *arg0, char *arg1, ..., NULL )
• int execle( char *pathname, char *arg0, char *arg1, ..., NULL, char *envp[] )
• int execlp( char *pathname, char *arg0, char *arg1, ..., NULL )
• int execlpe( char *pathname, char *arg0, char *arg1, ..., NULL, char *envp[] )
• int execv( char *pathname, *arg, NULL )
• int execve( char *pathname, *arg, NULL, char *envp[] )
• int execvp( char *pathname, *arg, NULL )
• int execvpe( char *pathname, *arg, NULL, char *envp[] )
• void _exit( int completioncode )
• int gsignal( int sig )
• int getpid( void )
• int spawnl( int mode, char *path, char *arg0, char *arg1, ..., NULL )
• int spawnle( int mode, char *path, char *arg0, char *arg1, ..., NULL, char *envp[] )
• int spawnlp( int mode, char *path, char *arg0, char *arg1, ..., NULL )
• int spawnlpe( int mode, char *path, char *arg0, char *arg1, ..., NULL, char *envp[] )
• int spawnv( int mode, char *path, char *argv )
• int spawnve( int mode, char *path, char *argv, char *envp[] )
• int spawnvp( int mode, char *path, char *argv )
• int spawnvpe( int mode, char *path, char *argv, char *envp[] )
• int (*ssignal( int sig, int (*action))) (void)
• void swab( char *src, char *dest, int nbytes )
• int system( const char *command )
• int raise( int sig )

Time and date functions

• char *asctime( const struct tm *tm )
• clock_t clock( void )
• char *ctime( const long *clock )
• double difftime( time_t time2, time_t time1 )
• struct tm *gmtime( const time_t *clock )
• struct tm *localtime( const time_t *clock )
• int stime( time_t *tp )
• char *_strdate( char *date )
• char *_strtime( char *time )
• time_t time( time_t *tloc )
• void tzset( void )
• int utime( char *path, struct utimbuf *times )

String and memory functions

You may also check the topic providing a summary of the memory manipulation functions and string manipulation functions.

• void *memccpy(void *dest, const void *src, int ch, size_t n)
• void *memchr( const void *s, int ch, size_t n )
• int memcmp( const void *s1, const void *s2, size_t n )
• void *memcpy( void *dest, const void *src, size_t n )
• int memicmp( const void *s1, const void *s2, size_t n )
• void *memmove( void *dest, const void *src, size_t n )
• void *memset( void *s, int ch, size_t n )
• void movedata( unsigned segsrc, unsigned offsrc, unsigned segdest, unsigned offdest, size_t n )
• void movmem( void *src, void *dest, unsigned len )
• void setmem( void *addr, int len, char value )
• char *stpcpy( char *dest, const char *src )
• char *strcat( char *dest, const char *src )
• char *strchr( const char *str, int c )
• int strcmp( const char *str1, const char *str2 )
• char *strcpy( char *dest, const char *src )
• size_t strcspn( const char *str1, const char *str2 )
• char *strdup( const char *str )
• char *_strerror( char *string )
• char *strerror( char *str )
• int stricmp( const char *str1, const char *str2 )
• size_t strlen( const char *str )
• char *strlwr( char *str )
• char *strncat( char *dest, const char *src, size_t maxlen )
• int strncmp( const char *str1, const char *str2, size_t maxlen )
• char *strncpy( char *dest, const char *src, size_t maxlen )
• int strnicmp( const char *str1, const char *str2, size_t maxlen )
• char *strnset( char *str, int ch, size_t n )
• char *strpbrk( const char *str1, const char *str2 )
• char *strrchr( const char *str, int c )
• char *strrev( char *str )
• char *strset( char *str, int ch )
• size_t strspn( const char *str1, const char *str2 )
• char *strstr( const char *anchor, const char *testpattern )
• double strtod( const char *str, char **endptr )
• char *strtok( char *str1, const char *str2 )
• long strtol( const char *str, char **endptr, int base )
• unsigned long strtoul( const char *s, char **endptr, int radix )
• char *strupr( char *str )

Math functions (math.h)

• double acos( double x )
• double asin( double x )
• double atan( double x )
• double tan( double y, double x )
• double cabs( struct complex z )
• double ceil( double x )
• double cos( double x )
• double cosh( double x )
• int dieeetomsbin( double *srcdbl, double *dstdbl )
• int dmsbintoieee( double *srcdbl, double *dstdbl )
• double exp( double x )
• double fabs( double x )
• int fieeetomsbin( float *srcflt, float *dstflt )
• double floor( double x )
• int fmsbintoieee( float *srcflt, float *dstflt )
• double fmod( double x, double y )
• double frexp( double value, int eptr )
• double hypot( double x, double y )
• double ldexp( double value, int exp )
• double log( double x )
• double log10( double x )
• double _matherr( _mexcep why, char *fun, double *arg1p, double *arg2p, double retv )
• int matherr( struct exception *e )
• double modf( double value, double *iptr )
• double poly( double x, int n, double coeff[] )
• double pow( double x, double y )
• double pow10( double x )
• double sin( double x )
• double sinh( double x )
• double sqrt( double x )
• double tan( double x )
• double tanh( double x )

Assertion library (assert.h)

• void assert( int test )

Type utilities (ctype.h)

• int isalnum( int c )
• int isalpha( int c )
• int isascii( int c )
• int iscntrl( int c )
• int isdigit( int c )
• int isgraph( int c )
• int islower( int c )
• int isprint( int c )
• int ispunct( int c )
• int isspace( int c )
• int isupper( int c )
• int isxdigit( int c )
• int toascii( int c )
• int _tolower( int c )
• int tolower( int c )
• int _toupper( int c )
• int toupper( int c )