Wi' lightsome heart I pu'd a rose
Frae aff its thorny tree,
And my fause luver stawmy rose,
But left the thorn wi' me.-Robert Burns, Ye Flowery Banks
We continue to bemoan the fact that debugging a large scientific program is more of a challenge than it has a right to be. In the next chapter we will discuss things you as a programmer can do to meet this challenge. Here we indicate some Unix tools which will help you debug your C, Fortran, or Pascal programs. One tool lets you keep your own books and just use the D compiler options to print out the information you need for debugging. Other tools call in outside help, namely debuggers. The most generally available debugger is dbx - or some similar combination of letters. This valuable tool is further improved by using it in an X Windows interface known as xde, and we recommend it highly.