1. itoa() converts an integer to a string.
2. ltoa() converts a long to a string.
3. ultoa() converts an unsigned long to a string.
4. sprintf() sends formatted output to a string, so it can be used to convert any type of values to string type.
#include<stdio.h>
#include<stdlib.h>
int main(void)
{
int num1 = 12345;
float num2 = 5.12;
char str1[20];
char str2[20];
itoa(num1, str1, 10); /* 10 radix value */
printf("integer = %d string = %s n", num1, str1);
sprintf(str2, "%f", num2);
printf("float = %f string = %s", num2, str2);
return 0;
}
// Output:
// integer = 12345 string = 12345
// float = 5.120000 string = 5.120000

The standard error(stderr) stream is the default destination for error messages and other 

diagnostic warnings. Like stdout, it is usually also directed to the output device of the 

standard console (generally, the screen).

strrchr() returns a pointer to the last occurrence of character in a string.
Example:

Output: The last position of '2' is 14.

rewind() takes the file pointer to the beginning of the file. so that the next I/O operation

 will take place at the beginning of the file.
Example: rewind(FilePointer);

strrchr() returns a pointer to the last occurrence of character in a string.

"fflush()" flush any buffered output associated with filename, which
is either a file opened for writing or a shell command for redirecting
output to a pipe or coprocess.

Example:
fflush(FilePointer);
fflush(NULL); flushes all streams.