1)IN RA MAX 

program abc;

uses crt;

var a,b,c,d,max:real;

begin

clrscr;

writeln('TIM SO LON NHAT TRONG BON SO A , B ,C , D');

write('nhap a=');

readln(a);

writerite('Nhap b='); 
     Readln(b); 
     Write('Nhap c='); 
     Readln(c);

Write('Nhap d='); 
     Readln(d); 
     max:=a; 
          If b>max then max:=b; 
          If c>max then max:=c; 
          if d>max then max:=d; 
     Writeln('So lon nhat la: ',max: 4: 2); 
Readln; 
END

 2)IN RA MIN 

Program TIM_SO_LON_NHAT;
Uses crt; 
Var a,b,c,d,min: real; 
BEGIN Clrscr; 
     Writeln('TIM SO NHO NHAT TRONG BON SO A, B, C, D'); 
     Write('Nhap a='); 
     Readln(a); 
     Write('Nhap b='); 
     Readln(b); 
     Write('Nhap c='); 
     Readln(c); 
     Write('Nhap d='); 
     Readln(d); 
     max:=a; 
          If b>max then min:=b; 
          If c>max then min:=c; 
          if d>max then min:=d; 
     Writeln('So lon nhat la: ',min: 4: 2); 
Readln; 
END.

uses crt;

var a, b, c, d, min, max : integer;

begin

clrscr;

write('Nhap 4 so a, b, c, d : '); readln(a, b, c, d);

max := a; min := a;

if b > max then max := b;

if c > max then max := c;

if d > max then max := d;

if b < min then min := b;

if c < min then min := c;

if d < min then min := d;

writeln('Max = ', max);

writeln('Min = ', min);

readln

end.