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#include<stdio.h>
#include<string.h>
void main()
{
 volatile char another='y';
 int num;
 while (another=='y') {
  printf("enter a number");
  fflush(stdin);
  scanf("%d",&num);
  printf("\nsquare of %d is %d",num,num*num);
  printf("\nWant to enter another number y/n? ");
  fflush(stdin);
  scanf("%c",&another);
 }
}

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scanf( " %c", &another );

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    while (getchar() != '\n');

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    while (getchar() != EOF);

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

#define BUFFSZ 96
// this should be large enough to read in any double value

/* read in a string */ 
double getd(FILE* in)
{
    char buffer[BUFSZ]; 
    char input;
    double value;
    int i = 0;

    bool eflag, dpflag;

     eflag = dpflag = false;

    do 
    {
        input = getc(in);

        if ('\n' == input)
        {
            return (INFINITY); // I would use NAN, but it isn't standard
        }
    }  
    while (!(isdigit(in)) && '-' != input );

    do
    {
        buffer[i] = input;
        ++i;    
        input = getc(in);
 
        // check for multiple exponent markers
        if ('E' == toupper(input))
        {
               if(eflag)
               {
                   break;
               }
               else
               {
                   eflag = true;
               }
        }
        // check for multiple decimal points
        else if ('.' == input)
        {
               if(dpflag)
               {
                   break;
               }
               else
               {
                   dpflag = true;
               }
        }

    }
    while ((BUFSZ > i) && ((isdigit(input) || ('E' == toupper(input)) || ('.' == input));

    // push the last char back into the stream 
    ungetc(input, in);

    return(strtod(buffer));
}

/* eats the characters until the next newline 
    and returns the number of characters 
*/
int eatline(FILE* in)
{
    int count = 0;
  
    while ('\n' != getc(in))
    {
         ++count;
    }
    return count;
}