C语言库函数 - C开头.docVIP

C语言库函数 - C开头 C语言函数 - C开头 函数名: cabs 功 能: 计算复数的绝对值 用 法: double cabs(struct complex z); 程序例: #include stdio.h #include math.h int main(void) { struct complex z; double val; z.x = 2.0; z.y = 1.0; val = cabs(z); printf(The absolute value of %.2lfi %.2lfj is %.2lf, z.x, z.y, val); return 0; } 函数名: calloc 功 能: 分配主存储器 用 法: void *calloc(size_t nelem, size_t elsize); 程序例: #include stdio.h #include alloc.h int main(void) { char *str = NULL; /* allocate memory for string */ str = calloc(10, sizeof(char)); /* copy Hello into string */ strcpy(str, Hello); /* display string */ printf(String is %s\n, str); /* free memory */ free(str); return 0; } 函数名: ceil 功 能: 向上舍入 用 法: double ceil(double x); 程序例: #include math.h #include stdio.h int main(void) { double number = 123.54; double down, up; down = floor(number); up = ceil(number); printf(original number %5.2lf\n, number); printf(number rounded down %5.2lf\n, down); printf(number rounded up %5.2lf\n, up); return 0; } 函数名: cgets 功 能: 从控制台读字符串 用 法: char *cgets(char *str); 程序例: #include stdio.h #include conio.h int main(void) { char buffer[83]; char *p; /* Theres space for 80 characters plus the NULL terminator */ buffer[0] = 81; printf(Input some chars:); p = cgets(buffer); printf(\ncgets read %d characters: \%s\\n, buffer[1], p); printf(The returned pointer is %p, buffer[0] is at %p\n, p, buffer); /* Leave room for 5 characters plus the NULL terminator */ buffer[0] = 6; printf(Input some chars:); p = cgets(buffer); printf(\ncgets read %d characters: \%s\\n, buffer[1], p); printf(The returned pointer is %p, buffer[0] is at %p\n, p, buffer); return 0; } 函数名: chdir 功 能: 改变工作目录 用 法: int chdir(const char *path); 程序例: #include stdio.h #include stdlib.h #include dir.h char old_dir[MAXDIR]; char new_dir[MAXDIR]; int main(void) {