{(* Eratosthenes Sieve Prime Number Program in PASCAL *)}
program primes;
uses crt;


{This is the original version from Byte, with only the modifications necessary
to allow it to compile under UCSD and a bell at the end.  
If you choose to report your results, 
PLEASE RUN IT AS IS!  It is a known fact that the speed of this version
can be significantly improved by turning off range checking and re-ordering
the declarations of the variables,  but this is the version which has been used
most and we desire consistantcy.  

Start timing by typing <cr> and stop at the bell.  gws}

{The results of this version on several systems have been reported on MUSUS.

System          UCSD version    Time (sec)
------          ------------    ----------

Sage II         IV.1            57     (68000 at 8 MHz)
WD uEngine      III.0           59     (fillchar is so slow on uE)

LSI-11/23       IV.01           92-122 (depends on memory speed)
LSI-11/23       II.0            105    (98 seconds under IV.01)
LSI-11/23       IV.1            107    (non-extended memory)
LSI-11/23       IV.1            128    (extended memory)

NEC APC         IV.1            144     8086 at 4.9 Mhz  extended memory

JONOS           IV.03 ?         162    (pretty good for a 4 MHz Z-80A)
NorthStar       I.5             183    (Z-80 at 4 MHz)
OSI C8P-DF      II.0  ?         197    (6502 at 2 MHz)
H-89            II.0            200    (4 MHz Z-80A)
LSI-11/2        IV.0            202
IBM PC          IV.03           203    (4.77 MHz 8088)
LSI-11/2        II.0            220

Apple ][        II.1            390    (1 MHz 6502)
H-89            II.0            455    (2 MHz Z-80)

}

{Feb. 2013 
  Minimal changes to run in MiniPacal:
    - added fillchar routine
    - lowercased
 /soegaard

  http://archive.org/stream/byte-magazine-1981-09/
  BYTE_Vol_06-09_1981-09_Artifical_Intelligence_djvu.txt
}

const
  size = 8190;
type
  flagarray = array [0..size] of boolean;
 
var
 flags : flagarray;
 i,prime,k,count,iter : integer;

procedure fillchar(fs:flagarray; n:integer; c:char);
var
  i:integer;
begin
  for i:=0 to n do
    fs[i]:=boolean(c);
end;
 
begin
for iter := 1 to 10 do 
  begin
  count := 0;
  fillchar(flags,high(flags),chr(1));
  for i := 0 to size do
    if flags[i] then 
      begin
      prime := i+i+3;
      k := i + prime;
      while k <= size do 
        begin
        flags[k] := false;
        k := k + prime
        end;
        count := count + 1;
      end;
  end;
  write(count, ' primes');
  ReadKey;
end.