// user managed array 
// (not good; should be done e.g. inside a struct)
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

  float *Pdata = NULL;   // to hold array of data
  int Psize;             // size of current block

void initialize(int initialPsize);
int set(int index, float value);
void doubleSize( ); 
void dump( );
void release( );

int main( ) 
{
   initialize( 5 ) ;
   int i;
   for(i=0; i<7; i++)
      set( i , sqrtf(i) );
   doubleSize();
   set(7, 9999);
   dump();
   return 0;
}

void initialize(int initialPsize) 
{
   Psize = initialPsize;
   Pdata = calloc( Psize, sizeof(float) );
}
   
int set(int index, float value)
{
   if( index < 0 || index>=Psize ) {
      return 0;
   }
   else {
      Pdata[index] = value;
      return 1;
   }
}
 
void doubleSize( )
{
   float *oldPdata = Pdata;
   Pdata = calloc( Psize*2, sizeof(float) );
   int i;
   for( i=0; i<Psize; i++)
      Pdata[i] = oldPdata[i]; 
   Psize *= 2;
   free( oldPdata );
}

void dump( )
{
   int i;
   for( i=0; i<Psize; i++)
      printf("%.2f  ", Pdata[i] );
   printf("\n");
}