#include <math.h>                                           
   #define   MAXSIZE    100                                    
                                                               
   main( )                                                     
   {                                                           
        int i,n;                                               
        floatvalue [MAXSIZE], deviation,                      
              sum,sumsqr,mean,variance,stddeviation;           
                                                               
        sum = sumsqr = n = 0 ;                                 
                                                               
        printf("Input values: input -1 to end \n");            
        for (i=1; i< MAXSIZE ; i++)                            
        {                                                      
            scanf("%f", &value[i]);                            
            if (value[i] == -1)                                
               break;                                          
            sum += value[i];                                   
            n += 1;                                            
        }                                                      
        mean = sum/(float)n;                                   
                                                               
        for (i = 1 ; i<= n; i++)                               
        {                                                      
            deviation = value[i] - mean;                       
            sumsqr += deviation * deviation;                   
        }                                                      
        variance = sumsqr/(float)n ;                           
        stddeviation = sqrt(variance) ;                        
                                                               
        printf("\nNumber of items : %d\n",n);                  
        printf("Mean : %f\n", mean);                           
        printf("Standard deviation : %f\n", stddeviation);     
   }                                                           
                                                               

   Output                                                      
                                                               
   Input values: input -1 to end                               
   65  9  27  78  12  20  33  49  -1                           
                                                               
   Number of items : 8                                         
   Mean : 36.625000                                            
   Standard deviation : 23.510303