struct {
          char name[20];
          char vornam[20];
          char wohnort[30];
          int alter;
          int plz;
          char Strasse[30];
          }adressen;

FILE *quelle;

.............

strcpy(adressen.name,"Bill");
strcpy(adressen.vornam,"Clinton");
strcpy(adressen.wohnort,"Washington D.C");
adressen.alter=55;
adressen.plz=232;
strcpy(adressen.Strasse,"7th Street");

...............

if((quelle=fopen("adres.dat","w+b")) == NULL)
..............

fwrite(&adressen, sizeof(adressen), 1, quelle);
..............