What is the purpose of fflush() function.

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).

Do like this fprintf(stdout, "%s %d %f", str, i, a);

stdio.h, which stands for "standard input/output header", is the header in the C standard library that contains macro definitions, constants, and declarations of functions and types used for various standard input and output operations.

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

Example:

#include <stdio.h>
#include <string.h>

int main()
{
    char str[30] = "12345678910111213";
    printf("The last position of '2' is %d.\n",
            strrchr(str, '2') - str);
    return 0;
}

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);

The randomize() function initializes the random number generator with a random value based on time. You can try the sample program given below in Turbo-C, it may not work as expected in other compilers.

/* Prints a random number in the range 0 to 99 */

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

int main(void)
{
    randomize();
    printf("Random number in the 0-99 range: %d\n", random (100));
    return 0;
}

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

Given 3.14 is a double constant.

To specify 3.14 as long double, we have to add L to the 3.14. (i.e 3.14L)

Given 3.14 is a double constant.
To specify 3.14 as float, we have to add f to the 3.14. (i.e 3.14f)