1.     WHERE conditions are applied before the data enters the input buffer while IF conditions are applied after the data enters the program data vector

2.     The type of variable Auto-Conversion happens when then data enters PDV as follow examples

data a;

input num char $;

cards;

    1   23

    3   23

    1   77

;

data b;

set a;

if char=23;;

run;

data c;

set a;

where char=23;

run;

data b1;

set a;

if num='1';;

run;

data c1;

set a;

where num='1';

run;