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函数名:?abort?

功??能:?异常终止一个进程?

用??法:?void?abort(void);?

程序例:?

#include?<stdio.h>?
#include?<stdlib.h>?
int?main(void)?
{?
??printf("Calling?abort()\n");?
??abort();?
??return?0;?/*?This?is?never?reached?*/?
}?
??
??

函数名:?abs?

功??能:?求整数的绝对值?

用??法:?int?abs(int?i);?

程序例:?

#include?<stdio.h>?
#include?<math.h>?
int?main(void)?
{?
??int?number?=?-1234;?
??printf("number:?%d??absolute?value:?%d\n",?number,?abs(number));?
??return?0;?
}?
??
??

函数名:?absread,?abswirte?

功??能:?绝对磁盘扇区读、写数据?

用??法:?int?absread(int?drive,?int?nsects,?int?sectno,?void?*buffer);?

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

程序例:?

/*?absread?example?*/?
#include?<stdio.h>?
#include?<conio.h>?
#include?<process.h>?
#include?<dos.h>?
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);?
}?
??
??
??

函数名:?access?

功??能:?确定文件的访问权限?

用??法:?int?access(const?char?*filename,?int?amode);?

程序例:?

#include?<stdio.h>?
#include?<io.h>?
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);?
}?
??

函数名:?acos?

功??能:?反余弦函数?

用??法:?double?acos(double?x);?

程序例:?

#include?<stdio.h>?
#include?<math.h>?
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;?
}?
??
??

函数名:?allocmem?

功??能:?分配DOS存储段?

用??法:?int?allocmem(unsigned?size,?unsigned?*seg);?

程序例:?

#include?<dos.h>?
#include?<alloc.h>?
#include?<stdio.h>?
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;?
}?
??
??

函数名:?arc?

功??能:?画一弧线?

用??法:?void?far?arc(int?x,?int?y,?int?stangle,?int?endangle,?int?radius);?

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?=?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;?
}?
??
??

函数名:?asctime?

功??能:?转换日期和时间为ASCII码?

用??法:?char?*asctime(const?struct?tm?*tblock);?

程序例:?

#include?<stdio.h>?
#include?<string.h>?
#include?<time.h>?
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;?
}?
??
??
??

函数名:?asin?

功??能:?反正弦函数?

用??法:?double?asin(double?x);?

程序例:?

#include?<stdio.h>?
#include?<math.h>?
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);?
}?
??
??
??

函数名:?assert?

功??能:?测试一个条件并可能使程序终止?

用??法:?void?assert(int?test);?

程序例:?

#include?<assert.h>?
#include?<stdio.h>?
#include?<stdlib.h>?
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;?
}?
??
??
??

函数名:?atan?

功??能:?反正切函数?

用??法:?double?atan(double?x);?

程序例:?

#include?<stdio.h>?
#include?<math.h>?
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);?
}?
??
??

函数名:?atan2?

功??能:?计算Y/X的反正切值?

用??法:?double?atan2(double?y,?double?x);?

程序例:?

#include?<stdio.h>?
#include?<math.h>?
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;?
}?
??
??

函数名:?atexit?

功??能:?注册终止函数?

用??法:?int?atexit(atexit_t?func);?

程序例:?

#include?<stdio.h>?
#include?<stdlib.h>?
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;?
}?
??
??
??

函数名:?atof?

功??能:?把字符串转换成浮点数?

用??法:?double?atof(const?char?*nptr);?

程序例:?

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

函数名:?atoi?

功??能:?把字符串转换成长整型数?

用??法:?int?atoi(const?char?*nptr);?

程序例:?

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

函数名:?atol?

功??能:?把字符串转换成长整型数?

用??法:?long?atol(const?char?*nptr);?

程序例:?

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