A mathematical function
When calling mathematical functions required in the source file package the following command line:
#include <math.h>
| Function prototype Description |
Features |
return value |
Explanation |
| int abs( int x) |
Seeking the absolute value of the integer x |
Calculation results |
|
| double fabs(double x) |
Double precision absolute value of real number x |
Calculation results |
|
| double acos(double x) |
Calcd cos-1 (x) of |
Calculation results |
x is in the range of -1 to 1 |
| double asin(double x) |
Calcd sin-1 (x) of |
Calculation results |
x is in the range of -1 to 1 |
| double atan(double x) |
Calcd tan-1 (x) of |
Calculation results |
|
| double atan2(double x) |
Calcd tan-1 (x / y) of |
Calculation results |
|
| double cos(double x) |
Calculating cos (x) value |
Calculation results |
x is in radians |
| double cosh(double x) |
Calculating cosh cosh (x) value |
Calculation results |
|
| double exp(double x) |
Evaluation of ex |
Calculation results |
|
| double fabs(double x) |
Double precision absolute value of real number x |
Calculation results |
|
| double floor(double x) |
Seeking no greater than double the maximum real number x is an integer |
|
|
| double fmod(double x,double y) |
Double the number of required I x / y divisible |
|
|
| double frexp(double val,int *exp) |
Val the double decomposition base 2 and the mantissa exponent n, i.e. val = x * 2n, n is stored in a variable referred to in exp |
Returns the number of bits x 0.5≤x<1 |
|
| double log(double x) |
Seeking ㏑x |
Calculation results |
x>0 |
| double log10(double x) |
Seeking log10x |
Calculation results |
x>0 |
| double modf(double val,double *ip) |
The double val decomposed into integer and fractional parts, stored in the integer part of a variable referred to in ip |
Returns the fractional part |
|
| double pow(double x,double y) |
Calculated value of xy |
Calculation results |
|
| double sin(double x) |
Calculate sin (x) value |
Calculation results |
x is in radians |
| double sinh(double x) |
Hyperbolic sine function sinh (x) calculation of the value of x |
Calculation results |
|
| double sqrt(double x) |
Calculate the square root of x |
Calculation results |
x≥0 |
| double tan(double x) |
Calculating tan (x) |
Calculation results |
|
| double tanh(double x) |
Calculating x hyperbolic tangent function tanh (x) value |
Calculation results |
|
Second, the character function
When you call a character function in the source file package requires the following command line:
#include <ctype.h>
| Function prototype Description |
Features |
return value |
| int isalnum(int ch) |
Ch check whether a letter or digit |
Yes, returns 1; otherwise it returns 0 |
| int isalpha(int ch) |
Check whether the letter ch |
Yes, returns 1; otherwise it returns 0 |
| int iscntrl(int ch) |
Check whether ch is a control character |
Yes, returns 1; otherwise it returns 0 |
| int isdigit(int ch) |
Check whether the digital ch |
Yes, returns 1; otherwise it returns 0 |
| int isgraph(int ch) |
Ch checks whether the value of the ASCII code to ox7e ox21 printable characters (i.e. no space character) |
Yes, returns 1; otherwise it returns 0 |
| int islower(int ch) |
Check the ch is a lowercase letter |
Yes, returns 1; otherwise it returns 0 |
| isprint you (you ch) |
Check whether ch to contain spaces, including printable characters |
Yes, returns 1; otherwise it returns 0 |
| int ispunct(int ch) |
In addition to checking whether ch spaces, letters, numbers, printable characters |
Yes, returns 1; otherwise it returns 0 |
| int isspace(int ch) |
Check whether ch spaces, tabs, or line breaks |
Yes, returns 1; otherwise it returns 0 |
| int isupper(int ch) |
Check the ch is an uppercase letter |
Yes, returns 1; otherwise it returns 0 |
| int isxdigit(int ch) |
Ch check whether the hexadecimal |
Yes, returns 1; otherwise it returns 0 |
| int tolower(int ch) |
Ch converted into lowercase letters |
Corresponding to the returned lowercase |
| int toupper(int ch) |
The letters converted to uppercase letters ch |
Returns uppercase corresponding |
Third, String Functions
When you call a character function in the source file package requires the following command line:
#include <string.h>
| Function prototype Description |
Features |
return value |
| char *strcat(char *s1,char *s2) |
String s1 s2 to the rear |
the address indicated by s1 |
| char *strchr(char *s,int ch) |
Referred to in s string to find the first character position appears ch |
The return address of the character found, can not find returns NULL |
| int strcmp(char *s1,char *s2) |
S1 and s2 referred to compare strings |
s1 <s2, returns negative; s1 = = s2, returns 0; s1> s2, returns a positive number |
| char *strcpy(char *s1,char *s2) |
把s2指向的串复制到s1指向的空间 |
s1 所指地址 |
| unsigned strlen(char *s) |
求字符串s的长度 |
返回串中字符（不计最后的'\0'）个数 |
| char *strstr(char *s1,char *s2) |
在s1所指字符串中，找出字符串s2第一次出现的位置 |
返回找到的字符串的地址，找不到返回NULL |
四、输入输出函数
调用字符函数时，要求在源文件中包下以下命令行：
#include <stdio.h>
| 函数原型说明 |
功能 |
返回值 |
| void clearer(FILE *fp) |
清除与文件指针fp有关的所有出错信息 |
无 |
| int fclose(FILE *fp) |
关闭fp所指的文件，释放文件缓冲区 |
出错返回非0，否则返回0 |
| int feof (FILE *fp) |
检查文件是否结束 |
遇文件结束返回非0，否则返回0 |
| int fgetc (FILE *fp) |
从fp所指的文件中取得下一个字符 |
出错返回EOF，否则返回所读字符 |
| char *fgets(char *buf,int n, FILE *fp) |
从fp所指的文件中读取一个长度为n-1的字符串，将其存入buf所指存储区 |
返回buf所指地址，若遇文件结束或出错返回NULL |
| FILE *fopen(char *filename,char *mode) |
以mode指定的方式打开名为filename的文件 |
成功，返回文件指针（文件信息区的起始地址），否则返回NULL |
| int fprintf(FILE *fp, char *format, args,…) |
把args,…的值以format指定的格式输出到fp指定的文件中 |
实际输出的字符数 |
| int fputc(char ch, FILE *fp) |
把ch中字符输出到fp指定的文件中 |
成功返回该字符，否则返回EOF |
| int fputs(char *str, FILE *fp) |
把str所指字符串输出到fp所指文件 |
成功返回非负整数，否则返回-1（EOF） |
| int fread(char *pt,unsigned size,unsigned n, FILE *fp) |
从fp所指文件中读取长度size为n个数据项存到pt所指文件 |
读取的数据项个数 |
| int fscanf (FILE *fp, char *format,args,…) |
从fp所指的文件中按format指定的格式把输入数据存入到args,…所指的内存中 |
已输入的数据个数，遇文件结束或出错返回0 |
| int fseek (FILE *fp,long offer,int base) |
移动fp所指文件的位置指针 |
成功返回当前位置，否则返回非0 |
| long ftell (FILE *fp) |
求出fp所指文件当前的读写位置 |
读写位置，出错返回 -1L |
| int fwrite(char *pt,unsigned size,unsigned n, FILE *fp) |
把pt所指向的n*size个字节输入到fp所指文件 |
输出的数据项个数 |
| int getc (FILE *fp) |
从fp所指文件中读取一个字符 |
返回所读字符，若出错或文件结束返回EOF |
| int getchar(void) |
从标准输入设备读取下一个字符 |
返回所读字符，若出错或文件结束返回-1 |
| char *gets(char *s) |
从标准设备读取一行字符串放入s所指存储区，用’\0’替换读入的换行符 |
返回s,出错返回NULL |
| int printf(char *format,args,…) |
把args,…的值以format指定的格式输出到标准输出设备 |
输出字符的个数 |
| int putc (int ch, FILE *fp) |
同fputc |
同fputc |
| int putchar(char ch) |
把ch输出到标准输出设备 |
返回输出的字符，若出错则返回EOF |
| int puts(char *str) |
把str所指字符串输出到标准设备，将’\0’转成回车换行符 |
返回换行符，若出错，返回EOF |
| int rename(char *oldname,char *newname) |
把oldname所指文件名改为newname所指文件名 |
成功返回0，出错返回-1 |
| void rewind(FILE *fp) |
将文件位置指针置于文件开头 |
无 |
| int scanf(char *format,args,…) |
从标准输入设备按format指定的格式把输入数据存入到args,…所指的内存中 |
已输入的数据的个数 |
五、动态分配函数和随机函数
调用字符函数时，要求在源文件中包下以下命令行：
#include <stdlib.h>
| 函数原型说明 |
功能 |
返回值 |
| void *calloc(unsigned n,unsigned size) |
分配n个数据项的内存空间，每个数据项的大小为size个字节 |
分配内存单元的起始地址；如不成功，返回0 |
| void *free(void *p) |
释放p所指的内存区 |
无 |
| void *malloc(unsigned size) |
分配size个字节的存储空间 |
分配内存空间的地址；如不成功，返回0 |
| void *realloc(void *p,unsigned size) |
把p所指内存区的大小改为size个字节 |
新分配内存空间的地址；如不成功，返回0 |
| int rand(void) |
产生0～32767的随机整数 |
返回一个随机整数 |
| void exit(int state) |
程序终止执行，返回调用过程，state为0正常终止，非0非正常终止 |
无 |
