How to Play the Classical Guitar
The Range of the classical guitar

Guitar strings can be loosened to produce a slightly lower note. In fact, the note of the open string 6 is often tuned one tone lower to produce a D note. With this tuning, the range of the guitar is extended by one note.

This range chart assumes that all strings can be played up to the 20th fret. The highest note will vary depending on the number of frets and the fret design of your guitar.
For example, if your guitar allows playing up to the 19th fret, the highest note for each string will be lowered by a semitone. If it allows up to the 18th fret, the highest note for each string will be lowered by a whole tone.