Perfect numbers: Difference between revisions

==={{header|PL/I-80}}===

<lang PL/I>perfect_search: procedure options (main);

%replace

search_limit by 10000,

true by '1'b,

false by '0'b;

dcl (k, found) fixed bin;

put skip list ('Searching for perfect numbers up to ');

put edit (search_limit) (f(5));

found = 0;

do k = 2 to search_limit;

if isperfect(k) then

do;

put skip list(k);

found = found + 1;

end;

end;

put skip list (found, ' perfect numbers were found');

/* return true if n is perfect, otherwise false */

isperfect: procedure(n) returns (bit(1));

dcl (n, sum, f1, f2) fixed bin;

sum = 1; /* 1 is a proper divisor of every number */

f1 = 2;

do while ((f1 * f1) < n);

if mod(n, f1) = 0 then

do;

sum = sum + f1;

f2 = n / f1;

/* don't double count identical co-factors! */

if f2 > f1 then sum = sum + f2;

end;

f1 = f1 + 1;

end;

return (sum = n);

end isperfect;

end perfect_search;</lang>

{{out}}

<pre>

Searching for perfect numbers up to 10000

6

28

496

8128

4 perfect numbers were found

</pre>