Что значит odd

Program ex1;
const
n=6 ;
m=6;
type dmyarray=array[1..n,1..m] of integer;
var i,j,l,k:integer;
a:dmyarray;
procedure print (var x:dmyarray);
var i,j:integer;
begin
for i:=1 to n do
for j:=1 to m do
write (x[i,j]:3);
writeln;
end;
begin
For l:=1 to 2*n-1 do{parallel`nux pobo4no`y}
begin
if l>n then{vu[1]e duagonalu}
begin
if odd(l) then
for i:=l-n+1 to n do
begin
k:=k+1;
a[i,l-i+1]:=k;
end
else
for i:=n downto l-n+1 do
begin
k:=k+1;
a[i,l-i+1]:=k;
end;
end
else if l<=n then{nu}{e duagonalu u na ne`y}
begin
if odd(l) then
for i:=1 to l do
begin
k:=k+1;
a[i,l-i+1]:=k;
end
else
for i:=l downto 1 do
begin
k:=k+1;
a[i,l-i+1]:=k;
end;
end;
end;
for i:=1 to n do
begin
for j:=1 to n do
write(a[i,j]:3);
writeln;
end;
readln
end.

Program ex1;
uses crt;
const
n=6 ;
type dmyarray=array[1..n,1..n] of integer;
procedure Init(var x:dmyarray);
var l,k,i,j:integer;
begin
For l:=1 to 2*n-1 do{parallel`nux pobo4no`y}
 begin
  if l>n then{vu[1]e duagonalu}
   begin
    if odd(l) then
    for i:=l-n+1 to n do
     begin
      k:=k+1;
      x[i,l-i+1]:=k;
     end
    else
     for i:=n downto l-n+1 do
      begin
       k:=k+1;
       x[i,l-i+1]:=k;
      end;
    end
  else if l<=n then{nu}{e duagonalu u na ne`y}
   begin
    if odd(l) then
    for i:=1 to l do
     begin
      k:=k+1;
      x[i,l-i+1]:=k;
     end
    else
     for i:=l downto 1 do
      begin
       k:=k+1;
       x[i,l-i+1]:=k;
      end;
    end;
 end;
end;
procedure print (var x:dmyarray);
var i,j:integer;
begin
for i:=1 to n do
 begin
  for j:=1 to n do
  write (x[i,j]:3);
  writeln;
 end;
end;
var a:dmyarray;
begin
Init(a);
Print(a);
readln
end.