数学函数2.txt

一些用到的函数 功能齐全

函数名: ecvt 
功  能: 把一个浮点数转换为字符串 
用  法: char ecvt(double value, int ndigit, int *decpt, int *sign); 
程序例: 
#include <stdlib.h> 
#include <stdio.h> 
#include <conio.h> 

int main(void) 
{ 
   char *string; 
   double value; 
   int dec, sign; 
   int ndig = 10; 

   clrscr(); 
   value = 9.876; 
   string = ecvt(value, ndig, &dec, &sign); 
   printf("string = %s      dec = %d \ 
   sign = %d\n", string, dec, sign); 

   value = -123.45; 
   ndig= 15; 
   string = ecvt(value,ndig,&dec,&sign); 
   printf("string = %s dec = %d sign = %d\n", 
   string, dec, sign); 
  

   value = 0.6789e5; /* scientific 
   notation */ 
   ndig = 5; 
   string = ecvt(value,ndig,&dec,&sign); 
   printf("string = %s           dec = %d\ 
   sign = %d\n", string, dec, sign); 

   return 0; 
} 
  
  

函数名: ellipse 
功  能: 画一椭圆 
用  法: void far ellipse(int x, int y, int stangle, int endangle, 
    int xradius, int yradius); 
程序例: 

#include <graphics.h> 
#include <stdlib.h> 
#include <stdio.h> 
#include <conio.h> 

int main(void) 
{ 
   /* request auto detection */ 
   int gdriver = DETECT, gmode, errorcode; 
   int midx, midy; 
   int stangle = 0, endangle = 360; 
   int xradius = 100, yradius = 50; 

   /* initialize graphics, local variables */ 
   initgraph(&gdriver, &gmode, ""); 

   /* read result of initialization */ 
   errorcode = graphresult(); 
   if (errorcode != grOk) 
   /* an error occurred */ 
   { 
      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 ellipse */ 
   ellipse(midx, midy, stangle, endangle, 
    xradius, yradius); 

   /* clean up */ 
   getch(); 
   closegraph(); 
   return 0; 
} 
  
  

函数名: enable 
功  能: 开放硬件中断 
用  法: void enable(void); 
程序例: 

/* ** NOTE: 
This is an interrupt service routine. You can NOT compile this program 
with Test Stack Overflow turned on and get an executable file which will 
operate correctly. 
*/ 

#include <stdio.h> 
#include <dos.h> 
#include <conio.h> 

/* The clock tick interrupt */ 
#define INTR 0X1C 

void interrupt ( *oldhandler)(void); 

int count=0; 

void interrupt handler(void) 
{ 
/* 
   disable interrupts during the handling of the interrupt 
*/ 
   disable(); 
/* increase the global counter */ 
   count++; 
/* 
   re enable interrupts at the end of the handler 
*/ 
   enable(); 
/* call the old routine */ 
   oldhandler(); 
} 

int main(void) 
{ 
/* save the old interrupt vector */ 
   oldhandler = getvect(INTR); 

/* install the new interrupt handler */ 
   setvect(INTR, handler); 

/* loop until the counter exceeds 20 */ 
   while (count < 20) 
      printf("count is %d\n",count); 

/* reset the old interrupt handler */ 
   setvect(INTR, oldhandler); 

   return 0; 
} 
  
  

函数名: eof 
功  能: 检测文件结束 
用  法: int eof(int *handle); 
程序例: 

#include <sys\stat.h> 
#include <string.h> 
#include <stdio.h> 
#include <fcntl.h> 
#include <io.h> 

int main(void) 
{ 
   int handle; 
   char msg[] = "This is a test"; 
   char ch; 

   /* create a file */ 
   handle = open("DUMMY.FIL", 
   O_CREAT | O_RDWR, 
   S_IREAD | S_IWRITE); 

   /* write some data to the file */ 
   write(handle, msg, strlen(msg)); 

   /* seek to the beginning of the file */ 
   lseek(handle, 0L, SEEK_SET); 

   /* 
      reads chars from the file until hit EOF 
   */ 
   do 
   { 
      read(handle, &ch, 1); 
      printf("%c", ch); 
   } while (!eof(handle)); 

   close(handle); 
   return 0; 
} 
  
  

函数名: exec... 
功  能: 装入并运行其它程序的函数 
用  法: int execl(char *pathname, char *arg0, arg1, ..., argn, NULL); 
 int execle(char *pathname, char *arg0, arg1, ..., argn, NULL, 
     char *envp[]); 
 int execlp(char *pathname, char *arg0, arg1, .., NULL); 
 int execple(char *pathname, char *arg0, arg1, ..., NULL, 
      char *envp[]); 
 int execv(char *pathname, char *argv[]); 
 int execve(char *pathname, char *argv[], char *envp[]); 
 int execvp(char *pathname, char *argv[]); 
 int execvpe(char *pathname, char *argv[], char *envp[]); 
程序例: 

/* execv example */ 
#include <process.h> 
#include <stdio.h> 
#include <errno.h> 

void main(int argc, char *argv[]) 
{ 
   int i; 

   printf("Command line arguments:\n"); 
   for (i=0; i<argc; i++) 
      printf("[%2d] : %s\n", i, argv[i]); 

   printf("About to exec child with arg1 arg2 ...\n"); 
   execv("CHILD.EXE", argv); 

   perror("exec error"); 

   exit(1); 
} 
  
  

函数名: exit 
功  能: 终止程序 
用  法: void exit(int status); 
程序例: 

#include <stdlib.h> 
#include <conio.h> 
#include <stdio.h> 

int main(void) 
{ 
   int status; 

   printf("Enter either 1 or 2\n"); 
   status = getch(); 
   /* Sets DOS errorlevel  */ 
   exit(status - '0'); 

/* Note: this line is never reached */ 
   return 0; 
} 
  
  

函数名: exp 
功  能: 指数函数 
用  法: double exp(double x); 
程序例: 

#include <stdio.h> 
#include <math.h> 

int main(void) 
{ 
   double result; 
   double x = 4.0; 

   result = exp(x); 
   printf("'e' raised to the power \ 
   of %lf (e ^ %lf) = %lf\n", 
   x, x, result); 

   return 0; 
} 
  

                             返回目录 
 




版权所有(C) 潇逸天地
Copyright by 潇 逸 1999 
建议用 IE4.0 800*600真彩色浏览本站以达到最好效果
网站制作：潇 逸(周 炜) 
  
  
函数名: fabs 
功  能: 返回浮点数的绝对值 
用  法: double fabs(double x); 
程序例: 

#include <stdio.h> 
#include <math.h> 

int main(void) 
{ 
   float  number = -1234.0; 

   printf("number: %f  absolute value: %f\n", 
   number, fabs(number)); 
   return 0; 
} 
  
  
  

函数名: farcalloc 
功  能: 从远堆栈中申请空间 
用  法: void far *farcalloc(unsigned long units, unsigned ling unitsz); 
程序例: 
#include <stdio.h> 
#include <alloc.h> 
#include <string.h> 
#include <dos.h> 

int main(void) 
{ 
   char far *fptr; 
   char *str = "Hello"; 

   /* allocate memory for the far pointer */ 
   fptr = farcalloc(10, sizeof(char)); 

   /* copy "Hello" into allocated memory */ 
   /* 
      Note: movedata is used because you 
      might be in a small data model, in 
      which case a normal string copy routine 
      can not be used since it assumes the 
      pointer size is near. 
   */ 
   movedata(FP_SEG(str), FP_OFF(str), 
     FP_SEG(fptr), FP_OFF(fptr), 
            strlen(str)); 

   /* display string (note the F modifier) */ 
   printf("Far string is: %Fs\n", fptr); 

   /* free the memory */ 
   farfree(fptr); 

   return 0; 
} 
  
  
  

函数名: farcoreleft 
功  能: 返回远堆中未作用存储区大小 
用  法: long farcoreleft(void); 
程序例: 

#include <stdio.h> 
#include <alloc.h> 

int main(void) 
{ 
   printf("The difference between the\ 
    highest allocated block in the\ 
           far\n"); 
   printf("heap and the top of the far heap\ 
           is: %lu bytes\n", farcoreleft()); 

   return 0; 
} 
  
  
  

函数名: farfree 
功  能: 从远堆中释放一块 
用  法: void farfree(void); 
程序例: 

#include <stdio.h> 
#include <alloc.h> 
#include <string.h> 
#include <dos.h> 

int main(void) 
{ 
   char far *fptr; 
   char *str = "Hello"; 

   /* allocate memory for the far pointer */ 
   fptr = farcalloc(10, sizeof(char)); 

   /* copy "Hello" into allocated memory */ 
   /* 
      Note: movedata is used because you might be in a small data model, 
      in which case a normal string copy routine can't be used since it 
      assumes the pointer size is near. 
   */ 
   movedata(FP_SEG(str), FP_OFF(str), 
            FP_SEG(fptr), FP_OFF(fptr), 
            strlen(str)); 

   /* display string (note the F modifier) */ 
   printf("Far string is: %Fs\n", fptr); 

   /* free the memory */ 
   farfree(fptr); 

   return 0; 
} 
  
  
  

函数名: farmalloc 
功  能: 从远堆中分配存储块 
用  法: void far *farmalloc(unsigned long size); 
程序例: 

#include <stdio.h> 
#include <alloc.h> 
#include <string.h> 
#include <dos.h> 

int main(void) 
{ 
   char far *fptr; 
   char *str = "Hello"; 

   /* allocate memory for the far pointer */ 
   fptr = farmalloc(10); 

   /* copy "Hello" into allocated memory */ 
   /* 
      Note: movedata is used because we might 
      be in a small data model, in which case 
      a normal string copy routine can not be 
      used since it assumes the pointer size 
      is near. 
   */ 
   movedata(FP_SEG(str), FP_OFF(str), 
     FP_SEG(fptr), FP_OFF(fptr), 
     strlen(str)); 

   /* display string (note the F modifier) */ 
   printf("Far string is: %Fs\n", fptr); 

   /* free the memory */ 
   farfree(fptr); 

   return 0; 
} 
  
  
  

函数名: farrealloc 
功  能: 调整远堆中的分配块 
用  法: void far *farrealloc(void far *block, unsigned long newsize); 
程序例: 

#include <stdio.h> 
#include <alloc.h> 

int main(void) 
{ 
   char far *fptr; 

   fptr = farmalloc(10); 
   printf("First address: %Fp\n", fptr); 
   fptr = farrealloc(fptr,20); 
   printf("New address  : %Fp\n", fptr); 
   farfree(fptr); 
   return 0; 
} 
  
  

函数名: fclose 
功  能: 关闭一个流 
用  法: int fclose(FILE *stream); 
程序例: 

#include <string.h> 
#include <stdio.h> 

int main(void) 
{ 
   FILE *fp; 
   char buf[11] = "0123456789"; 

   /* create a file containing 10 bytes */ 
   fp = fopen("DUMMY.FIL", "w"); 
   fwrite(&buf, strlen(buf), 1, fp); 

   /* close the file */ 
   fclose(fp); 
   return 0; 
} 
  
  
  

函数名: fcloseall 
功  能: 关闭打开流 
用  法: int fcloseall(void); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   int streams_closed; 

   /* open two streams */ 
   fopen("DUMMY.ONE", "w"); 
   fopen("DUMMY.TWO", "w"); 

   /* close the open streams */ 
   streams_closed = fcloseall(); 

   if (streams_closed == EOF) 
      /* issue an error message */ 
      perror("Error"); 
   else 
      /* print result of fcloseall() function */ 
      printf("%d streams were closed.\n", streams_closed); 

   return 0; 
} 
  
  

函数名: fcvt 
功  能: 把一个浮点数转换为字符串 
用  法: char *fcvt(double value, int ndigit, int *decpt, int *sign); 
程序例: 

#include <stdlib.h> 
#include <stdio.h> 
#include <conio.h> 

int main(void) 
{ 
   char *string; 
   double value; 
   int dec, sign; 
   int ndig = 10; 

   clrscr(); 
   value = 9.876; 
   string = ecvt(value, ndig, &dec, &sign); 
   printf("string = %s      dec = %d \ 
          sign = %d\n", string, dec, sign); 

   value = -123.45; 
   ndig= 15; 
   string = ecvt(value,ndig,&dec,&sign); 
   printf("string = %s dec = %d sign = %d\n", 
          string, dec, sign); 
  

   value = 0.6789e5; /* scientific 
                        notation */ 
   ndig = 5; 
   string = ecvt(value,ndig,&dec,&sign); 
   printf("string = %s           dec = %d\ 
          sign = %d\n", string, dec, sign); 

   return 0; 
} 
  
  
  

函数名: fdopen 
功  能: 把流与一个文件句柄相接 
用  法: FILE *fdopen(int handle, char *type); 
程序例: 

#include <sys\stat.h> 
#include <stdio.h> 
#include <fcntl.h> 
#include <io.h> 

int main(void) 
{ 
   int handle; 
   FILE *stream; 

   /* open a file */ 
   handle = open("DUMMY.FIL", O_CREAT, 
    S_IREAD | S_IWRITE);