//chapter 3
//example 3.22
//page 120
printf("\n")
printf("given")
Vo=5;Vf=.7;Iz=5*10^-3;Il=1*10^-3;E=20;
Vz=Vo-Vf
R1=(E-Vo)/(Il+Iz);
printf("zener diode resistance si %dohm\n",R1)