I have been trying to write a program in Pascal (free pascal compiler, Lazarus IDE) that solves an uncompleted entered sudoku. I am moderately new to programming/pascal/lazarus, and so I have no idea how to use the debugging features. I have read through the code several times but I can't see what the problem is. Any help would be greatly appreciated!

```
program sudoku;
var
input : array[1..9, 1..9] of integer;
cell : array[1..9, 1..9, 1..9] of integer;
output : array[1..9, 1..9] of integer;
cposs : array[1..9, 1..9, 1..9] of integer;
cloop, cloop2, rloop, rloop2, bloop, bloop2, loop, loop2, loop3, c, d : integer;
cloop3, rloop3, bloop3 : integer;
cloop4, rloop4, bloop4 : integer;
cloop5, rloop5, bloop5 : integer;
solved : boolean;
{$R *.res}
begin
{sets all items of input array to 0}
for loop := 1 to 9 do
begin
for loop2 := 1 to 9 do
input[loop2,loop] := 0;
end;
{sets all items of cell array to 10}
for loop := 1 to 9 do
begin
for loop2 := 1 to 9 do
begin
for loop3 := 1 to 9 do
begin
cell[loop3,loop2,loop] := 10;
end;
end;
end;
{instructions}
writeln('== Sudoku Solver ==':50);
writeln;
writeln;
writeln('Please enter the numbers of your sudoku from left to right, one row at a time from top to bottom, WITH A SPACE BETWEEN EACH CHARACTER, pressing enter after each row. If the cell is empty, please write a 0.');
writeln;
{reading inputs}
for rloop := 1 to 9 do
begin
for cloop := 1 to 9 do
read( input[cloop,rloop] );
end;
{copies inputs to "cell" array, and adds box position}
for rloop := 1 to 9 do
begin
for cloop := 1 to 9 do
begin
if cloop in [1..3] then
if rloop in [1..3] then
cell[cloop,rloop,1] := input[cloop,rloop] else
if rloop in [4..6] then
cell[cloop,rloop,4] := input[cloop,rloop] else
if rloop in [7..9] then
cell[cloop,rloop,7] := input[cloop,rloop];
if cloop in [4..6] then
if rloop in [1..3] then
cell[cloop,rloop,2] := input[cloop,rloop] else
if rloop in [4..6] then
cell[cloop,rloop,5] := input[cloop,rloop] else
if rloop in [7..9] then
cell[cloop,rloop,8] := input[cloop,rloop];
if cloop in [7..9] then
if rloop in [1..3] then
cell[cloop,rloop,3] := input[cloop,rloop] else
if rloop in [4..6] then
cell[cloop,rloop,6] := input[cloop,rloop] else
if rloop in [7..9] then
cell[cloop,rloop,9] := input[cloop,rloop];
end;
end;
repeat
c := 0;
d := 0;
{the big block}
for bloop := 1 to 9 do
begin
for rloop := 1 to 9 do
begin
for cloop := 1 to 9 do
begin
{checks if it is possible to have cell in that place
by checking if a value from input has been copied
over (the value wont be 10}
if cell[cloop,rloop,bloop] < 10 then
begin
if cell[cloop,rloop,bloop] > 0 then
begin
{no possibility for that number in the cells in this box}
for bloop2 := 1 to 9 do
begin
for rloop2 := 1 to 9 do
begin
for cloop2 := 1 to 9 do
begin
if cell[cloop2,rloop2,bloop2] < 10 then
begin
if bloop2 = bloop then
cposs[cloop2, rloop2, cell[cloop,rloop,bloop] ] := 1;
end;
end;
end;
end;
{no possibility for that number in the cells in that row}
for bloop3 := 1 to 9 do
begin
for rloop3 := 1 to 9 do
begin
for cloop3 := 1 to 9 do
begin
if cell[cloop3,rloop3,bloop3] < 10 then
begin
if rloop3 = rloop then
cposs[cloop3, rloop3, cell[cloop,rloop,bloop] ] := 1;
end;
end;
end;
end;
{no possibility for that number in the cells in that column}
for bloop4 := 1 to 9 do
begin
for rloop4 := 1 to 9 do
begin
for cloop4 := 1 to 9 do
begin
if cell[cloop4,rloop4,bloop4] < 10 then
begin
if cloop4 = cloop then
cposs[cloop4, rloop4, cell[cloop,rloop,bloop] ] := 1;
end;
end;
end;
end;
end;
end;
{checks if cell has only one possible answer}
for loop := 1 to 9 do
begin
if cposs[cloop,rloop,loop] = 0 then
c := c + 1;
end;
if c = 1 then
begin
for loop := 1 to 9 do
begin
if cposs[cloop, rloop, loop] = 0 then
cell[cloop,rloop,bloop] := loop;
end;
end;
end;
end;
end;
{checks if sudoku is finished}
for bloop5 := 1 to 9 do
begin
for rloop5 := 1 to 9 do
begin
for cloop5 := 1 to 9 do
begin
if cell[cloop5, rloop5, bloop5] = 0 then
d := d + 1;
end;
end;
end;
if d = 0 then solved := true;
until solved = true;
{copying}
for bloop := 1 to 9 do
begin
for rloop := 1 to 9 do
begin
for cloop := 1 to 9 do
begin
if cell[cloop,rloop,bloop] < 10 then
begin
output[cloop,rloop] := cell[cloop,rloop,bloop];
end;
end;
end;
end;
writeln;
{printing}
for rloop := 1 to 9 do
begin
for cloop := 1 to 9 do
begin
write(output[cloop,rloop],' ');
end;
writeln;
end;
writeln;
writeln('Solved!');
readln;
readln;
end.
```