5

program IPR;
uses CRT;

var
reg,regOut,initial:integer;
opt:char;

Procedure Reg13;
var
key:char;
begin
clrscr;
{print value of register 13}
port[$3d4]:=$13;
reg:=port[$3d5];
initial:=port[$3d5];
writeln('Register 13 has value = ',reg);
{change value of register 13}
key:='a';
repeat
writeln('To increase value of register 13 enter m');
writeln('To decrease value of register 13 enter l');
writeln('To go to main menu enter b');
readln(key);
clrscr;
case key of
'm': begin
reg:=reg+1;
port[$3d4]:=$13;
port[$3d5]:=reg;
port[$3d4]:=$13;
regOut:=port[$3d5];
writeln;
writeln('Register 13 has value =',regOut);
end;
'l': begin
reg:=reg-1;
port[$3d4]:=$13;
port[$3d5]:=reg;
port[$3d4]:=$13;
regOut:=port[$3d5];
writeln;
writeln('Register 13 has value =',regOut);
end;
end;
until key='b';
port[$3d4]:=$13;
port[$3d5]:=initial; {return initial value of register 13}
end;

Procedure RegC;
var
key:char;
begin
clrscr;
{print value of register C}
port[$3d4]:=$c;
reg:=port[$3d5];
initial:=port[$3d5];
writeln('Register C matters = ',reg);
{change value of register C}
key:='a';
repeat
writeln('To increase the value of register C enter m');
writeln('To decrease the value of register C enter l');
writeln('To go to the main menu, enter b');
readln(key);
clrscr;
case key of
'm': begin
reg:=reg+1;
port[$3d4]:=$c;
port[$3d5]:=reg;
port[$3d4]:=$c;
regOut:=port[$3d5];
writeln;
writeln('Register C matters =',regOut);
end;
'l': begin
reg:=reg-1;
port[$3d4]:=$c;
port[$3d5]:=reg;
port[$3d4]:=$c;
regOut:=port[$3d5];
writeln;
writeln('Register C matters =',regOut);
end;
end;
until key='b';
port[$3d4]:=$c;
port[$3d5]:=initial; {return initial value of register C}
end;

Procedure RegD;
var
key:char;
begin
clrscr;
{print value of register D}
port[$3d4]:=$d;
reg:=port[$3d5];
initial:=port[$3d5];
writeln('Register D matters = ',reg);
{change value of register D}
key:='a';
repeat
writeln('To increase the value of register D enter m');
writeln('To decrease the value of register D enter l');
writeln('To go to the main menu, enter b');
readln(key);
clrscr;
case key of
'm': begin
reg:=reg+1;
port[$3d4]:=$d;
port[$3d5]:=reg;
port[$3d4]:=$d;
regOut:=port[$3d5];
writeln;
writeln('Register D matters =',regOut);
end;
'l': begin
reg:=reg-1;
port[$3d4]:=$d;
port[$3d5]:=reg;
port[$3d4]:=$d;
regOut:=port[$3d5];
writeln;
writeln('Register D matters =',regOut);
end;
end;
until key='b';
port[$3d4]:=$d;
port[$3d5]:=initial; {return initial value of register D}
end;

begin
clrscr;
repeat
writeln('Select register number, press Enter');
writeln('1 - 13');
writeln('2 - C');
writeln('3 - D');
writeln('Exit - enter 0');
readln(opt);
case opt of
'1': Reg13;
'2': RegC;
'3': RegD;
Else
writeln('Invalid registration number');
end;
until opt='0';
end.