This C language function ---

This C language function ---

Function Name: abort

Function: terminates a process abnormally.

Usage: void abort (void );

Program example:

#include 
 
   #include 
  
    int main(void) {   printf("Calling abort()\n");   abort();   return 0; /* This is never reached */ }     
  
 

Function Name: abs

Function: Calculate the absolute value of an integer.

Usage: int abs (int I );

Program example:

#include 
 
   #include 
  
    int main(void) {   int number = -1234;   printf("number: %d  absolute value: %d\n", number, abs(number));   return 0; }     
  
 

Function Name: absread, abswirte

Functions: Read and Write Data in absolute disk sectors

Usage: int absread (int drive, int nsects, int sectno, void * buffer );

 int abswrite(int drive, int nsects, in tsectno, void *buffer); 

Program example:

/* absread example */ #include 
 
   #include 
  
    #include 
   
     #include 
    
      int main(void) {   int i, strt, ch_out, sector;   char buf[512];   printf("Insert a diskette into drive A and press any key\n");   getch();   sector = 0;   if (absread(0, 1, sector, &buf) != 0)   {      perror("Disk problem");      exit(1);   }   printf("Read OK\n");   strt = 3;   for (i=0; i<80; i++)   {      ch_out = buf[strt+i];      putchar(ch_out);   }   printf("\n");   return(0); }       
    
   
  
 

Function Name: access

Skill: determine the object access permission

Usage: int access (const char * filename, int amode );

Program example:

#include 
 
   #include 
  
    int file_exists(char *filename); int main(void) {   printf("Does NOTEXIST.FIL exist: %s\n",   file_exists("NOTEXISTS.FIL") ? "YES" : "NO");   return 0; } int file_exists(char *filename) {   return (access(filename, 0) == 0); }   
  
 

Function Name: acos

Function: arccosine Function

Usage: double acos (double x );

Program example:

#include 
 
   #include 
  
    int main(void) {   double result;   double x = 0.5;   result = acos(x);   printf("The arc cosine of %lf is %lf\n", x, result);   return 0; }     
  
 

Function Name: allocmem

Function: allocate DOS storage segments

Usage: int allocmem (unsigned size, unsigned * seg );

Program example:

#include 
 
   #include  #include 
  
    int main(void) {   unsigned int size, segp;   int stat;   size = 64; /* (64 x 16) = 1024 bytes */   stat = allocmem(size, &segp);   if (stat == -1)      printf("Allocated memory at segment: %x\n", segp);   else      printf("Failed: maximum number of paragraphs available is %u\n",             stat);   return 0; }     
  
 

Function Name: arc

Power: draw an arc

Usage: void far arc (int x, int y, int stangle, int endangle, int radius );

Program example:

#include 
 
   #include 
  
    #include 
   
     #include 
    
      int main(void) {     /* request auto detection */    int gdriver = DETECT, gmode, errorcode;    int midx, midy;    int stangle = 45, endangle = 135;    int radius = 100;    /* initialize graphics and local variables */    initgraph(&gdriver, &gmode, "");    /* read result of initialization */    errorcode = graphresult();    /* an error occurred */    if (errorcode != grOk)    {       printf("Graphics error: %s\n", grapherrormsg(errorcode));       printf("Press any key to halt:");       getch();       exit(1);    /* terminate with an error code */    }    midx = getmaxx() / 2;    midy = getmaxy() / 2;    setcolor(getmaxcolor());    /* draw arc */    arc(midx, midy, stangle, endangle, radius);    /* clean up */    getch();    closegraph();    return 0; }     
    
   
  
 

Function Name: asctime

Function: Convert the date and time into ASCII codes.

Usage: char * asctime (const struct tm * tblock );

Program example:

#include 
 
   #include 
  
    #include 
   
     int main(void) {    struct tm t;    char str[80];    /* sample loading of tm structure  */    t.tm_sec    = 1;  /* Seconds */    t.tm_min    = 30; /* Minutes */    t.tm_hour   = 9;  /* Hour */    t.tm_mday   = 22; /* Day of the Month  */    t.tm_mon    = 11; /* Month */    t.tm_year   = 56; /* Year - does not include century */    t.tm_wday   = 4;  /* Day of the week  */    t.tm_yday   = 0;  /* Does not show in asctime  */    t.tm_isdst  = 0;  /* Is Daylight SavTime; does not show in asctime */    /* converts structure to null terminated    string */    strcpy(str, asctime(&t));    printf("%s\n", str);    return 0; }       
   
  
 

Function Name: asin

Power: arcsin Function

Usage: double asin (double x );

Program example:

#include 
 
   #include 
  
    int main(void) {    double result;    double x = 0.5;    result = asin(x);    printf("The arc sin of %lf is %lf\n", x, result);    return(0); }       
  
 

Function Name: assert

Skill: test a condition and possibly terminate the program

Usage: void assert (int test );

Program example:

#include  #include 
 
   #include 
  
    struct ITEM {    int key;    int value; }; /* add item to list, make sure list is not null */ void additem(struct ITEM *itemptr) {    assert(itemptr != NULL);    /* add item to list */ } int main(void) {    additem(NULL);    return 0; }       
  
 

Function Name: atan

Function: returns the arc tangent function.

Usage: double atan (double x );

Program example:

#include 
 
   #include 
  
    int main(void) {    double result;    double x = 0.5;    result = atan(x);    printf("The arc tangent of %lf is %lf\n", x, result);    return(0); }     
  
 

Function Name: atan2

Function: Calculate the arc tangent value of Y/X.

Usage: double atan2 (double y, double x );

Program example:

#include 
 
   #include 
  
    int main(void) {    double result;    double x = 90.0, y = 45.0;    result = atan2(y, x);    printf("The arc tangent ratio of %lf is %lf\n", (y / x), result);    return 0; }     
  
 

Function Name: atexit

Function: register the termination function.

Usage: int atexit (atexit_t func );

Program example:

#include 
 
   #include 
  
    void exit_fn1(void) {    printf("Exit function #1 called\n"); } void exit_fn2(void) {    printf("Exit function #2 called\n"); } int main(void) {    /* post exit function #1 */    atexit(exit_fn1);    /* post exit function #2 */    atexit(exit_fn2);    return 0; }       
  
 

Function Name: atof

Function: converts a string to a floating point number.

Usage: double atof (const char * nptr );

Program example:

#include 
 
   #include 
  
    int main(void) {    float f;    char *str = "12345.67";    f = atof(str);    printf("string = %s float = %f\n", str, f);    return 0; }     
  
 

Function Name: atoi

Function: converts a string to an integer.

Usage: int atoi (const char * nptr );

Program example:

#include 
 
   #include 
  
    int main(void) {    int n;    char *str = "12345.67";    n = atoi(str);    printf("string = %s integer = %d\n", str, n);    return 0; }     
  
 

Function Name: atol

Function: converts a string to an integer.

Usage: long atol (const char * nptr );

Program example:

#include 
 
   #include 
  
    int main(void) {    long l;    char *str = "98765432";    l = atol(lstr);    printf("string = %s integer = %ld\n", str, l);    return(0); }   
  
 

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