In music notation, da capo is abbreviated "D.C." and is placed just above the staff at the end of a section or piece. It indicates that the piece should repeat a second time from the beginning, and is usually used instead of a repeat sign when an entire lengthy piece is to be repeated. The phrase means "from the top" in Italian.
When written with a staff, it looks something like this (compete with time signature and a quarter note scale):
/\ D.C.
---| /----------------------------|---------------------||
|/ | | ||
---/------------------------------|---|----|------------||
/| 4 | | | | * ||
-/-|/\--------------------|----|--|---|----|---*---|----||
| | | 4 | | | | | * | | ||
|--|--|--------|-----|----|----|--|--*--------|----|----||
\ | | | | | * | | | ||
--\|_/---------|-----|---*--------|-----------|---------||
| | *
\| -*--