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Classification function, in which the function library is ctype.h
If ch is a letter ('A'-'Z',' a'-'z'), Int isalpha(int ch) returns a non-zero value, otherwise it returns 0.
Int isalnum(int ch) If ch is a letter ('A'-'Z',' a'-'z') or a number ('0'-'9'), it returns a non-zero value, otherwise it returns 0.
If ch is a character (0- 127 in ASCII code), Int isASCII(int ch) returns a non-zero value, otherwise it returns 0.
Int iscntrl(int ch) If ch is an invalid character (0x7F) or a common control character (0x00-0x 1F), it returns a non-zero value, otherwise it returns 0.
If ch is a number ('0'-'9'), Int isdigit(int ch) returns a non-zero value, otherwise it returns 0.
If ch is a printable character (excluding spaces) (0x2 1-0x7E), Int isgraph(int ch) returns a non-zero value, otherwise it returns 0.
If ch is lowercase ('a'-'z'), Int islower(int ch) returns a non-zero value, otherwise it returns 0.
If ch is a printable character (0x20-0x7E), Int isprint(int ch) returns a non-zero value, otherwise it returns 0.
If ch is a punctuation character (0x00-0x 1F), intipoint (intch) returns a non-zero value, otherwise it returns 0.
Int isspace(int ch) If ch is a space ('), horizontal tab ('\ t'), carriage return ('\ r'), line feed ('\ f'), vertical tab ('\ v'), line feed ('\ n'), it will return a non-zero value, otherwise.
If ch is a capital letter ('A'-'Z'), Int isupper(int ch) returns a non-zero value, otherwise it returns 0.
If ch is 16 ('0'-'9',' A'-'F',' a'-'f'), then int is xdiguity(int ch) returns a non-zero value, otherwise it returns 0.
Int tolower(int ch) If ch is an uppercase letter ('A'-'Z'), the corresponding lowercase letter ('a'-'z') is returned.
Int toupper(int ch) If ch is lowercase ('a'-'z'), the corresponding uppercase ('A'-'Z') is returned.
Mathematical function, in which the function library is math.h, stdlib.h, string.h, float.h
Int abs(int i) returns the absolute value of integer parameter i.
Double cabs(struct complex znum) returns the absolute value of complex znum.
Double fabs(double x) returns the absolute value of the double-precision parameter x.
Long labs(long n) returns the absolute value of the long integer parameter n.
Double e xp(double x) returns the value of the exponential function ex.
Doublefrexp (double value, int * eptr) returns the value of x in value=x*2n, where n is stored in eptr.
double ldexp(double value，int exp)； Returns the value of value*2exp.
Double log(double x) returns the value of logex.
Double log 10 (double x) returns the value of log 10x.
Double pow(double x, double y) returns the value of xy.
Double pow 10(int p) returns the value of 10p.
Double sqrt(double x) returns the root of X.
Doublecacos (doublex) returns the cosine of x, cos- 1(x), where x is radian.
Doublesin (doublex) returns the sine of x- 1 (x), where x is radian.
Double atan(double x) returns the arc tangent tan- 1(x) value of x, where x is radian.
Double atan2(double y, double x) returns the arc tangent tan- 1(x) value of y/x, where x of y is radian.
Double cos(double x) returns the cosine cos(x) value of x, where x is radian.
Double sin(double x) returns the sine sin(x) value of x, where x is radian.
Double tan(double x) returns the tangent tan(x) value of x, where x is radian.
Double cosh(double x) returns the hyperbolic cosine of x, where x is radian.
Double sinh(double x) returns the hyperbolic sine sinh(x) value of x, where x is radian.
Double tanh(double x) returns the hyperbolic tangent tanh(x) value of x, where x is radian.
Double hypot(double x, double y) returns the length (z) of the hypotenuse of a right triangle, where x and y are the lengths of the right side, and z2=x2+y2.
Double ceil(double x) returns the smallest integer not less than x.
Double floor(double x) returns the largest integer not greater than x.
Void srand (unsigned seed) initializes the random number generator.
Interland () generates a random number and returns it.
Doublepoly (double x, int n, double c []) generates polynomials from parameters.
Double MODF (double value, double * iptr) decomposes double-precision values into mantissa and order.
Double fmod(double x, double y) returns the remainder of x/y.
Double Frexp (double value, int * eptr) divides double-precision values into mantissa and order.
Double atof(char *nptr) converts the string nptr into a floating-point number and returns the floating-point number.
Double atoi(char *nptr) converts the string nptr into an integer and returns the integer.
Doubletall (char * nptr) converts the string nptr into an integer and returns the integer.
char *ecvt(double value，int ndigit，int *decpt，int *sign)
Converts a floating-point value to a string and returns the string.
char *fcvt(double value，int ndigit，int *decpt，int *sign)
Converts a floating-point value to a string and returns the string.
char *gcvt(double value，int ndigit，char *buf)
Convert the numeric value into a string and store it in buf, and return the pointer to buf.
Char *ultoa (unsigned long integer, char *string, int radix)
Converts an unsigned integer value to a string and returns the string, where radix is the radix used in the conversion.
Char *ltoa (long value, char * string, int radix)
Converts a long integer value to a string and returns the string, where radix is the radix used in the conversion.
Char *itoa (integer value, char * string, integer radix)
Converts an integer value to a string, and radix stores it in the string, where radix is the radix used in the conversion.
Double atof(char *nptr) converts the string nptr into a double-precision number and returns the number, and returns 0 if there is an error.
Int atoi(char *nptr) converts the string nptr into an integer and returns the number. Returning 0 indicates an error.
Long atol(char *nptr) converts the string nptr into an integer and returns this number, and returns 0 when an error occurs.
Double strod (char * str, char * * endptr) converts the string str into a double-precision number and returns the number.
Long str(char * str, char * * endptr, intbase) converts the string str into a long integer and returns the number.
Int matherr(struct exception *e) function, which allows users to correct mathematical errors and return information (unnecessary).
double _matherr(_mexcep why，char *fun，double *arg 1p，double *arg2p，double retval)
User can modify the function of returning information of mathematical errors (unnecessary).
Unsigned int _clear87 () clears the floating-point status word and returns to the original floating-point status.
Void _fpreset () reinitializes the floating-point math package.
Unsigned int _status87 () returns a floating-point status word.
Directory functions, in which the function libraries are dir.h and dos.h
Int chdir(char *path) takes the specified directory path (such as "C:\\WPS") as the current working directory, and returns 0 successfully.
int findfirst(char *pathname，struct ffblk *ffblk，int attrib)
Found the specified file and successfully returned 0.
Pathname is the specified directory name and file name, such as "C:\\WPS\\TXT".
Ffblk is a designated structure for saving file information, and its definition is as follows:
┏━━━━━━━━━━━━━━━━━━┓
┃struct· frank offers
┃{ ┃
┃char ff _ reserved[2 1]； /*DOS reserved word */┃
Char ff _ attrib/* File Properties */Quotation
┃ International time; /* Document Time */Quotation
Int ff _ fdate/* file date */quotation
┃ Long ff _ fsize/* file length */quotation
┃char ff _ name[ 13]； /* file name */quotation
┃} ┃
┗━━━━━━━━━━━━━━━━━━┛
Attrib is a file attribute represented by the following characters
┏━━━━━━━━━┳━━━━━━━━┓
┃FA_RDONLY read-only file┃ ┃FA_LABEL volume label┃
┃FA_HIDDEN hides the file┃ ┃FA_DIREC directory┃
┃FA_SYSTEM system file ┃FA_ARCH file ┃.
┗━━━━━━━━━┻━━━━━━━━┛
Example:
struct ffblk ff
findfirst("*。 wps”、& ampff，FA _ r donly)；
Int findnext(struct ffblk *ffblk) gets the file matching finddirst, and returns 0 successfully.
void fumerge(char *path，char *drive，char *dir，char *name，char *ext)
This function is composed of drivers (c letters (c:, a:, etc. ), path directory (\TC, \BC\LIB, etc. ), file name (TC, WPS, etc. ) and extension ext (. EXE，。 COM and so on. ) to form a file name and store it in the path.
int fnsplit(char *path，char *drive，char *dir，char *name，char *ext)
This function decomposes the file name path into drives (c letters (c:, a:, and so on). ), path directory (\TC, \BC\LIB, etc. ), file name (TC, WPS, etc. ) and extension ext (. EXE，。 Com and so on. ) and store them in the corresponding variables.
int getcurdir(int drive，char *direc)
This function returns the current working directory name of the specified drive. 0 was successfully returned.
A drive specified by drive (0= current, 1=A, 2=B, 3=C, etc.). )
Direc saves variables that specify the current working path of the drive.
The function Char *getcwd(char *buf, iint n) gets the current working directory and stores it in buf until the length of n bytes is. The error returned NULL.
Int getdisk () gets the currently used drive and returns an integer (0=A, 1=B, 2=C, and so on. ).
Int setdisk(int drive) sets the drive to be used (0 = a, 1 = b, 2 = c, and so on. ) and returns the total number of available drives.
Int mkdir(char *pathname) creates a new directory pathname and successfully returns 0.
Int rmdir(char *pathname) deletes a directory pathname and returns 0 successfully.
Char *mktemp(char *template) constructs a file name that does not exist in the current directory but exists in the template.
Char *searchPATH(char *pathname) uses MSDOS to find the path where the file name is located. This function uses the path variable of DOS, and returns NULL if the file is not found.
Process function, in which the function libraries are stdlib.h and process.h
Void abort () writes the termination message to stderr by calling _exit (exit code is 3) and terminates the program abnormally. No return value
Int exec… loads and runs other programs.
int execl(char *pathname，char *arg0，char *arg 1，…，char *argn，NULL)
int execle(char *pathname，char *arg0，char *arg 1，…，char *argn，NULL，char *envp[])
int execlp(char *pathname，char *arg0，char *arg 1，…，NULL)
int execlpe(char *pathname，char *arg0，char *arg 1，…，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[])
The exec function family loads and runs the program pathname, and passes the parameters arg0 (arg 1, arg2, argv [], envp []) to the subroutine, and returns-1 if there is an error.
In the family of exec functions, after adding the suffixes L, V, P, E to exec, the specified function will have certain computing power.
When there is a suffix p, the function can use DOS path variables to find subroutine files.
L, the number of parameters passed in the function is fixed.
V, the number of parameters passed in the function is not fixed.
E, the function passes the specified parameter envp, allowing the environment of the subprocess to be changed.
If there is no suffix e, the subprocess will use the environment of the current program.
Void _exit(int status) terminates the current program without cleaning up the site.
Void exit(int status) terminates the current program, closes all files, writes the output of the buffer (waits for the output), calls the "exit function" of any register, and returns no value.
Intspawn ... run subroutine
int spawnl(int mode，char *pathname，char *arg0，char *arg 1，…，char *argn，NULL)
int spawnle(int mode，char *pathname，char *arg0，char *arg 1，…，char *argn，NULL，char *envp[])
int spawnlp(int mode，char *pathname，char *arg0，char *arg 1，…，char *argn，NULL)
int spawnlpe(int mode，char *pathname，char *arg0，char *arg 1，…，char *argn，NULL，char *envp[])
Intspanv (int mode, char *pathname, char *argv[])
int spawnve(int mode，char *pathname，char *argv[]，char *envp[])
Int spawnvp(int mode, char *pathname, char *argv[])
int spawnvpe(int mode，char *pathname，char *argv[]，char *envp[])
The spawn function family runs the subroutine pathname in mode mode and passes the parameters arg0 (arg 1, arg2, argv [], envp []) to the subroutine. Returns-1 when an error occurs.
Mode is running mode:
P_WAIT mode means that the subroutine returns to this program after running.
P_NOWAIT means to run this program while the subroutine is running (unavailable).
P_OVERLAY means to run the subroutine after this program exits.
In spawn function family, after suffixes L, V, P, E are added to spawn, the specified function will have certain computing power.
When there is suffix p, the function uses DOS path to find subroutine files.
L, the number of parameters passed by the function is fixed.
V, the number of parameters passed by the function is not fixed.
E, the specified parameter envp can be passed to the subroutine, allowing to change the running environment of the subroutine.
Without the suffix e, the subroutine will use the environment of the program.
Int system (char * command)
Pass the MSDOS command to DOS to execute the conversion subroutine, and the function libraries include math.h, stdlib.h, ctype.h and float.h
char *ecvt(double value，int ndigit，int *decpt，int *sign)
Converts a floating-point value to a string and returns the string.
char *fcvt(double value，int ndigit，int *decpt，int *sign)
Converts a floating-point value to a string and returns the string.
char *gcvt(double value，int ndigit，char *buf)
Convert the numeric value into a string and store it in buf, and return the pointer to buf.
Char *ultoa (unsigned long integer, char *string, int radix)
Converts an unsigned integer value to a string and returns the string, where radix is the radix used in the conversion.
Char *ltoa (long integer value, char * string, integer radix)
Converts a long integer value to a string and returns the string, where radix is the radix used in the conversion.
Char *itoa (integer value, char * string, integer radix)
Converts an integer value to a string, and radix stores it in the string, where radix is the radix used in the conversion.
Double atof(char *nptr) converts the string nptr into a double-precision number and returns the number, and returns 0 if there is an error.
Int atoi(char *nptr) converts the string nptr into an integer and returns the number. Returning 0 indicates an error.
Long atol(char *nptr) converts the string nptr into an integer and returns this number, and returns 0 when an error occurs.
Double strtod(char *str, char **endptr)
Converts the string str to a double-precision number and returns the number.
long strtol(char *str，char **endptr，int base)
Converts the string str to a long integer and returns the number.
Int toASCII(int c) returns the corresponding ASCII code of c.
Int tolower(int ch) If ch is an uppercase letter ('A'-'Z'), the corresponding lowercase letter ('a'- 'z') is returned.
Int _tolower(int ch) returns the lowercase letters ('a'-'z') corresponding to ch.
Int toupper(int ch) If ch is lowercase ('a'-'z'), the corresponding uppercase ('A'- 'Z') is returned.
Int _toupper(int ch) returns the capital letter ('A'-'Z') corresponding to ch.
Diagnostic functions, in which the function libraries are assert.h and math.h
Void assert(int test) is a macro expanded into an if statement. If the test fails, it will display a message and terminate the program abnormally, with no return value.
Void perror(char *string) this function will display the latest error message in the format of string: error message.
Char *strerror(char *str) This function returns the latest error message in the format of string str: error message.
Int matherr (structural exception *e)
User can modify the function of returning information of mathematical errors (unnecessary).
double _matherr(_mexcep why，char *fun，double *arg 1p，double *arg2p，double retval)
User can modify the function of returning information of mathematical errors (unnecessary).
I/O subroutine with io.h, conio.h, stat.h, dos.h, stdio.h and signal.h function libraries.
This function returns the last keystroke.
Int fgetchar () reads a character from the console (keyboard) and displays it on the screen.
Int getch () reads a character from the console (keyboard) and does not display it on the screen.
Int putch () writes a character to the console (keyboard).
Int getchar () reads a character from the console (keyboard) and displays it on the screen.
Int putchar () writes a character to the console (keyboard).
Int getche () reads a character from the console (keyboard) and displays it on the screen.
Int ungetch(int c) returns the character c to the console (keyboard).
Char *cgets(char *string) reads strings from the console (keyboard) and stores them in strings.
int scanf(char *format[，argument…])
Read a string from the console, assign a value to each parameter, and output it by BIOS.
Int vscanf(char * format, Valist parameter)
Read a string from the console, assign values to each parameter, output by BIOS, and get parameters from validparam.
int cscanf(char *format[，argument…])
Read a string from the console, assign values to each parameter respectively, and directly operate the console. For example, when a display displays a character, it is displayed in a direct-write mode.
int sscanf(char *string，char *format[，argument，…])
Assign a value to each parameter through a string.
int vsscanf(char *string，char *format，Vlist param)
Assign a value to each parameter through a string, and the parameter is obtained from Vlist param.
Int puts(char *string) sends a string to the console (monitor) and uses BIOS to output it.
Void cputs(char *string) sends a string to the monitor to directly operate the console. For example, the monitor is displayed in write-through mode.
int printf(char *format[，argument，...])
Send the formatted string to the console (monitor) and output it using BIOS.
Int vprintf(char * format, validparam)
Send the formatted string to the console (monitor), use BIOS for output, and get parameters from validparam.
int cprintf(char *format[，argument，...])
Send the formatted string to the console (monitor) and directly operate the console. For example, the display is displayed at the direct writing frequency.
Int vcprintf(char * format, Valist parameter)
Send the formatted string to the console (monitor) and directly operate the console. For example, the display is displayed in direct write mode, and the parameters are obtained from validparam.
int sprintf(char *string，char *format[，argument，…])
Rewrite the contents of the string string into a formatted string.
int vsprintf(char *string，char *format，Valist param)
Rewrite the contents of the string into a formatted string, and the parameters are obtained from validparam.
Intrename (char * oldname, char * newname) changes the old name of the file to a new name.
int ioctl(int handle，int cmd[，int *argdx，int argcx])
This function is used to control input/output devices. Please refer to the following table:
┌———┬————————————————————————————┐
│cmd value │ function │
├———┼————————————————————————————┤
│ 0 │ Take out the equipment information │
│ 1 │ Set device information │.
│ 2 │ read argcx bytes into the address pointed by argdx │.
│ 3 │ Write argcx bytes at the address indicated by argdx │.
│ 4 │ Except the handle, it is used as the equipment number (0= current, 1=A, etc. ), the same as when cmd=2.
│ 5 │ Except the handle, it is used as the equipment number (0= current, 1=A, etc. ), as when cmd=3 │.
│ 6 │ Take the input state │
│ 7 │ Take the output status │
│ 8 │ Test interchangeability; Only for DOS 3.x │.
│ 1 1 │ resets the recalculation count of sharing conflicts; Only for DOS 3.x │.
└———┴————————————————————————————┘
Int (* ssignal (int sig, int (* action)) () () executes software signal (unnecessary).
Int gsignal(int sig) executes software signals (not required).
Int _ open (char * pathname, int access) opens a file for reading or writing, and then presses Access to determine whether to read or write the file. See the table below for access values.
┌——————┬————————————————————┐
│ Access value │ Meaning │
├——————┼————————————————————┤
│O _ r only reads files
│O_WRONLY │ Writing files │
O _ rdwr │ both reading and writing │
│O_NOINHERIT │ If the file is not passed to the subroutine, include it.
│O_DENYALL │ Only files that must be accessed during the current processing are allowed │
│O_DENYWRITE │ Read only from any other open file │
O _ denyread can only be written from any other open file.
│O_DENYNONE │ Allow other * * * to enjoy the opened file │.
└——————┴————————————————————┘
Intopen (char * pathname, in access[, int permit]) opens a file to read or write, and then presses access to determine whether to read or write the file. See the table below for access values.
┌————┬————————————————————┐
│ Access value │ Meaning │
├————┼————————————————————┤
│O _ r only reads files
│O_WRONLY│ Writing files │
O _ rdwr │ both reading and writing │
│O_NDELAY│ not used; Compatibility with UNIX system
│O_APPEND│ read and write, but it is always added at the end of the file every time it is written │.
│O_CREAT │ If the file exists, this sign is useless; If it does not exist, please create a new file.
│O_TRUNC │ If the file exists, its length is truncated to 0, and its attributes remain unchanged │.
│O_EXCL │ Not used; Compatibility with UNIX system
│O_BINARY│ This flag can display files opened in binary mode.
│O_TEXT │ This sign can be used to display files opened in text.
└————┴————————————————————┘
Permiss is a file attribute and can be the following values:
S_IWRITE allows writing S_IREAD allows reading S_IREAD|S_IWRITE allows reading and writing.
Int creat (char * filename, int permiss) creates a new file name and sets the read-write property.
Permiss is read-write and can be the following values
S_IWRITE allows writing S_IREAD allows reading S_IREAD|S_IWRITE allows reading and writing.
Int _ creat (char * filename, int attrib) creates a new file name and sets file properties.
Attrib is a file attribute and can be the following values
FA _ RDONLY read-only FA_HIDDEN hides the FA_SYSTEM system.
Intcreatnew (char * filenamt, IntAttrib) creates a new file name and sets file properties.
Attrib is a file attribute and can be the following values
FA _ RDONLY read-only FA_HIDDEN hides the FA_SYSTEM system.
Intcreattemp (char * filenamt, intattrib) creates a new file name and sets file properties.
Attrib is a file attribute and can be the following values
FA _ RDONLY read-only FA_HIDDEN hides the FA_SYSTEM system.
Intread (int handle, void * buf, int nbyte) reads nbyte characters from a file with a file number handle and stores them in buf.
Int _ read (int handle, void * buf, int nbyte) reads nbyte characters from the file with the file number handle, stores them in buf, and directly calls MSDOS to operate.
Int write(in handle, void * buf, intnbyte) writes nbyte characters in buf to a file with the file number as handle.
Int _ write (int handle, void * buf, int nbyte) writes nbyte characters in buf to a file with the file number as handle.
Copy a file to handle the pointer and return the pointer.
Int dup2(int handle, int newhandle) copies the file processing pointer handle to the newhandle.
Int eof(int *handle) checks whether the file ends, and returns 1 when it ends, otherwise returns 0.
Long filelongth(int handle) returns the file length, and handle is the file number.
Intsetmode (int handle, unsigned mode) is used to set the opening mode of the file and the number handle of the file.
int getftime(int handle，struct ftime *ftime)
Read the file time with the file number handle, and store the file time in the ftime structure, and return 0 successfully. The FTIME structure is as follows:
┌—————————————————┐
│ structure ftime \
│{ │
│ unsigned ft _ tsec: 5; /* seconds */│
Unsigned ft _ min: 6; /* points */│.
│ unsigned ft _ hour: 5; /* when */│。
│ unsigned ft _ day: 5; /* days */│.
│ unsigned ft _ month: 4; /* Month */│
│ unsigned ft _ year:1; /* year-1980*/ │.
│} │
└—————————————————┘
Intsetftime(in handle, structftime * ftime) rewrites the file time with the file number handle,
The new time is in the ftime structure. 0 returned successfully. The structure of ftime is as follows:
┌—————————————————┐
│ structure ftime \
│{ │
│ unsigned ft _ tsec: 5; /* seconds */│
Unsigned ft _ min: 6; /* points */│.
│ unsigned ft _ hour: 5; /* when */│。
│ unsigned ft _ day: 5; /* Day */│
│ unsigned ft _ month: 4; /* Month */│
│ unsigned ft _ year:1; /* year-1980*/ │.
│} │
└—————————————————┘
long lseek(int handle，long offset，int fromwhere)
This function moves the file pointer with the file number handle to the offset byte after fromwhere.
SEEK_SET file switch SEEK_CUR current position SEEK_END file ends.
Long tell(int handle) returns a file pointer with a file number handle, which is expressed in bytes.
Int isatty(int handle) is used to get the type of device handle.
Intlock (int handle, long offset, long length) blocks the file * * *.
Intunlock (int handle, long offset, long length) opens the block of file * * *.
Int close(int handle) closes the file processing represented by handle, which is from _creat, creat,
Call the obtained file processing in one of creatnew, creattemp, dup, dup2, _open and open.
0 or-1 was successfully returned, which can be used for UNIX systems.
Int _close(int handle) closes the file processing represented by handle, which is from _creat, creat,
Call the obtained file processing in one of creatnew, creattemp, dup, dup2, _open and open.
0 returned successfully, otherwise-1 is returned, which can only be used in MSDOS system.
File * fopen (char * filename, char * type) opens a file name, and the opening method is type.
And return a pointer to this file. Type can add a suffix to the following string.
┌——┬————┬———————┬————————┐
│ Type │ Readability │ Text/binary file │ Create new file/open old file │
├——┼————┼———————┼————————┤
│r │ Reading │ Text │ Opening old files │
│w │ Writing │ Text │ Creating a New Document │
│a │ Add │ Text │ Open it if it is available, and build it if it is not.
│r+ │ Read/Write │ Unlimited │ Open │
W+ read/write, unlimited, create new file.
│a+ │ Read/Add │ Unlimited │ Open it if you have it, and create a new one if you don't have it.
└——┴————┴———————┴————————┘
Suffixes that can be added are T and B. Adding B means that the file is operated in binary form, and T is not necessary.
For example: ┌—————————————┐
│ # contains & ltstdio.h & gt│.
│main() │
│{ │
│FILE * FP； │
│ fp=fopen("C:\\WPS\\WPS。 EXE”、“r+b”)； │
└——————————————————┘
FILE *fdopen(int ahndle，char *type)
FILE *freopen (character * file name, character * type, file * stream)
Int getc(FILE *stream) reads a character from the stream and returns it.
Writes a character ch to the stream.
Int getw(FILE *stream) reads an integer from the stream and returns an EOF error.
Int putw(int w, FILE *stream) writes an integer to the stream stream.
Int ungetc(char c, FILE *stream) returns the character c to the stream, and the character read next time will be C.
Int fgetc(FILE *stream) reads a character from the stream and returns it.
Int fputc(int ch, FILE *stream) writes the character ch.