A more efficient modification of the numter code may be used with 
the holes numbered by geometric progression - 1, 2, 4, 8, 16, 32, etc. 
In this case the decimel system is not used. Instead tkere is just one 
bank of holes and it includes as many holes as are needed to reach the 
desired capacity. The number 119 is notched in the following illustra- 
tion using the geometric progression system. (Simply notch holes such 
that the sum of their code numbers equals the desired number. In this 
case the numbers 64, 32, 16, 4, 2 and 1 add up to 119.) Note that only 
7 holes are needed to reach a capacity of 119 in this case. With the 
decimal system, 12 holes would be needed for the same capacity. 

There are many modificetions possible in coding wita comolnavions 
of notch-positions. Occasionally data which at first appeer impossible 
to code within the scope of the notch-card system are finally found to 
be capable of coding when the right combinations are used, Combinations 
may also be used with some forms of direct coding. For exemple, in a 
set of data containing information on several species of cold-water 
fish, and also on several warm-water species, the same holes can be 
used for either cold-water or warm-water fish, provided the two categor- 
ies will never appear simultaneously. Thus, if data from high mountain 
lakes are used in conjunction with data from farm ponds stocked with 
warm-water fish, and it is determined that the two classes of fish will 
. not appear simultaneously, an arrangement such as the one shown may be 
used., The trout are represented by three notch positions. The warm-water 
OC OOD OO @ @O0 6 0 
O Rb Bg 
Osr Ba . 
Otl Cr 

Rb - Rainbow 
Br - Fastern Brook 
Ll = Loch Leven 
Be - Bluegill 
Ba - Basa 
Cr = Crappie 



fish are represented by the same three positions plus a fourth position. 
The fourth position serves as a "key-shift." If it is punched, the code 
is for werm-weter fish. If it is not punched, the code is for trout. 
In sorting, one needles first the "key-shift™* position to separate 
trout from warm-water fish, then sorts according to species as desired. 
