var data[20]={0};           <---- inicializace with 0
	data[0]=2.1;
	data[19]=19.0;
	printf("\n%f %f",data[0],data[19]);

	memset(data,0,sizeof(var)*20);     <---- set all cell in data to 0 
	printf("\n%f %f",data[0],data[19]);  < --- looks OK