The type record lists the atom type number and the group number for every atom in the descriptor. The format is:

type	Natom
	atomtype1		grouptype1
	...		...

The type record starts with the keyword type followed by the number of type records N_atom. N_atom must be at least as large as the number of atoms declared in the header line of the descriptor file. Following the header line are N_atom pairs of number; the first number in the pair is the type number for the atom atomtype and the second number is the group membership number grouptype. The type number is used to categorize atoms. This is primarily (but not exclusively) used to define the non-bond parameters. The group (residue) membership number is currently not used to determine any physical quantities.

The atom type number (and group membership number) should be in a continuous range starting from 1. If you have gaps in your atom type numbers you will be listing more parameters for non-bond terms than is necessary. Example:

type 9

3   1
2   1
2   1
3   2
1   2
2   3
3   3
3   3
1   3

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A type record for a system containing no more than 9 atoms.There are three atom types and three groups. The first three atoms belong to the first group and have atom types 3, 2 and 2 respectively.