Nikon D1 Manual page 35

When the exposure remaining count reaches 0
When there is not enough memory available on the compact flash-
memory card to store further photographs at current settings, the
exposure remaining count will show zero and the Cd (card) indicator
in the viewfinder and the CARD indicators in the control panels will
flash. In this case you will need to delete photographs (see
"Playback") or insert another memory card (see "Insert the Memory
Card" in this chapter) before more photographs can be taken.
Note
The frame number shown in the control panel on top of the camera corresponds to the
number of photographs in the current folder. When a new folder is created, the current
frame number will return to 1. New folders are created when:
• the number of photographs in the current folder reaches the maximum of 999
• a file number of 999 is reached in sequential numbering mode (see "Custom
Settings," item 29)
• you create a new folder using the NEW option in the FOLDERS menu (see
"Playback: The Playback Menu"
22
First Steps: Take a Photograph