Pentax K-X Operating Manual page 35

You can select a method for assigning the folder names for storing images.
Date
PENTX
Set in [Folder Name] of the [_k Set-up 2]
menu (p.240).
The two digits of the month and day on which the picture was taken
are assigned as the folder name in the form of [xxx_MMDD]. [xxx] is
a sequential number from 100 to 999. [MMDD] (month and day)
appears according to the display style set in [Date Adjustment]
(p.244). (default setting)
Example) 101_0125: Folder for pictures taken on January 25th
The folder name is assigned in the form of [xxxPENTX].
Example) 101PENTX
m m
J_ 2:; 4
Brightness Level +-0
LCD Color Tuning
Video Out NTSC
USB Connection MSC
You can select a method for assigning the file number of an image when
saved to a new folder. Select [_ or [] for [File No.] in [Memory] (p.260) of
the [1_1 Rec. Mode 4] menu.
The file number of the last image saved to the previous folder is saved
and subsequent images are assigned sequential file numbers even if
a new folder is created.
The file number of the first image saved to a folder returns to 0001
[]
each time a new folder is created for saving images.
When the number Of storable images exceeds 500, Captured images are
divided into folders of 500 images each. However, in Exposure Bracketing
shooting, images will be stored in the same folde r unti! shooting is completed;
even if the number of images exceeds 500.