math.h常用函数
int abs (int x);
double acos (double x);
double asin (double x);
double atan (double x);
double atan2 (double y, double x);
double atof (const char *s);
double ceil (double x);
double cos (double x);
double cosh (double x);
double exp (double x);
double fabs (double x);
double floor (double x);
double fmod (double x, double y);
double frexp (double x, int *exponent);
long labs (long x);
double ldexp (double x, int exponent);
double log (double x);
double log10 (double x);
double modf (double x, double *ipart);
double pow (double x, double y);
double sin (double x);
double sinh (double x);
double sqrt (double x);
double tan (double x);
double tanh (double x);
stdio.h常用函数包括
int fclose (FILE *stream);
int fflush (FILE *stream);
int fgetc (FILE *stream);
int fgetpos (FILE *stream, fpos_t *pos);
char * fgets (char *s, int n, FILE *stream);
FILE * fopen (const char *path, const char *mode);
int fprintf (FILE *stream, const char *format, ...);
int fputc (int c, FILE *stream);
int fputs (const char *s, FILE *stream);
size_t fread (void *ptr, size_t size, size_t n, FILE *stream);
FILE * freopen (const char *path, const char *mode,
FILE *stream);
int fscanf (FILE *stream, const char *format, ...);
int fseek (FILE *stream, long offset, int whence);
int fsetpos (FILE *stream, const fpos_t *pos);
long ftell (FILE *stream);
size_t fwrite (const void *ptr, size_t size, size_t n,
FILE *stream);
int printf (const char *format, ...);
int puts (const char *s);
int rename (const char *oldname, const char *newname);
void rewind (FILE *stream);
int scanf (const char *format, ...);
stdlib.h常用函数包括
stdlib 头文件里包含了C、C++语言的一些函数
该文件包含了的C语言标准库函数的定义
stdlib.h里面定义了五种类型、一些宏和通用工具函数。类型例如size_t、wchar_t、div_t、ldiv_t和lldiv_t；宏例如EXIT_FAILURE、EXIT_SUCCESS、RAND_MAX和MB_CUR_MAX等等；常用的函数如malloc()、calloc()、realloc()、free()、system()、atoi()、atol()、rand()、srand()、exit()等等。具体的内容你自己可以打开编译器的include目录里面的stdlib.h头文件看看
int abs (int x);
int atexit (atexit_t func);
double atof (const char *s);
int atoi (const char *s);
long atol (const char *s);
void * bsearch(const void *key, const void *base,
size_t nelem, size_t width,
int (*fcmp)());
void * calloc (size_t nitems, size_t size);
div_t div (int numer, int denom);
void exit (int status);
void free (void *block);
char * getenv (const char *name);
long labs (long x);
ldiv_t ldiv (long numer, long denom);
void * malloc (size_t size);
void qsort (void *base, size_t nelem, size_t width,
int (*fcmp)());
int rand (void);
void * realloc(void *block, size_t size);
void srand (unsigned seed);
double strtod (const char *s, char **endptr);
long strtol (const char *s, char **endptr, int radix);
unsigned long strtoul (const char *s, char **endptr, int radix);
int system (const char *command);
max(a,b) (((a) > (b)) ? (a) : (b))
min(a,b) (((a) < (b)) ? (a) : (b))
random(num) (rand() % (num))
randomize() srand((unsigned)time(NULL))
string.h常用函数包括：
char * stpcpy (char *dest, const char *src);
char * strcat (char *dest, const char *src);
char * strchr (const char *s, int c);
int strcmp (const char *s1, const char *s2);
char * strcpy (char *dest, const char *src);
size_t strcspn (const char *s1, const char *s2);
char * strdup (const char *s);
char * strerror(int errnum);
conio.h不是C标准库中的头文件。
conio是Console Input/Output（控制台输入输出）的简写，其中定义了通过控制台进行数据输入和数据输出的函数，主要是一些用户通过按键盘产生的对应操作，比如getch()函数等等。
包含的函数
cgets(char *);
cprintf(const char *, ...);
cputs(const char *);
cscanf(const char *, ...);
inp(unsigned short);
inpw(unsigned short);
getch(void);
getche(void);
kbhit(void);
outp(unsigned short, int);
outpw(unsigned short, unsigned short);
putch(int);
ungetch(int);
void _Cdecl clreol (void);
void _Cdecl clrscr (void);
void _Cdecl delline (void);
int _Cdecl gettext (int left, int top, int right, int bottom,
void *destin);
void _Cdecl gettextinfo (struct text_info *r);
void _Cdecl gotoxy (int x, int y);
void _Cdecl highvideo (void);
void _Cdecl insline (void);
void _Cdecl lowvideo (void);
int _Cdecl movetext (int left, int top, int right, int bottom,
int destleft, int desttop);
void _Cdecl normvideo (void);
int _Cdecl puttext (int left, int top, int right, int bottom,
void *source);
void _Cdecl textattr (int newattr);
void _Cdecl textbackground (int newcolor);
void _Cdecl textcolor (int newcolor);
void _Cdecl textmode (int newmode);
int _Cdecl wherex (void);
int _Cdecl wherey (void);
void _Cdecl window (int left, int top, int right, int bottom);
har *_Cdecl cgets (char *str);
int _Cdecl cprintf (const char *format, ...);
int _Cdecl cputs (const char *str);
int _Cdecl cscanf (const char *format, ...);
int _Cdecl getch (void);
int _Cdecl getche (void);
char *_Cdecl getpass (const char *prompt);
int _Cdecl kbhit (void);
int _Cdecl putch (int c);
int _Cdecl ungetch (int ch);
C语言头文件中包含的函数,布布扣,bubuko.com
C语言头文件中包含的函数
原文：http://blog.csdn.net/pipisorry/article/details/38662805
