The

The `S` switch is one of the parameters in the structure `nhead` in the directory of the ``library'` file, and its purpose
is the tell the significance of some other parameters in `nhead`,
namely, *X*_{1}, *X*_{2}, *X*_{3}, and *X*_{4}. For an explanation of `nhead` see Section 3.2.3.

**0:**- There is no
*X*data. **1:**- The parameter
*X*_{1}is the excitation level in Mev. **2:**- These are pre-equilibrium and unresolved
direct-interaction processes, and there is no
*X*data. Note for example, that the`ENDL`library has two separate^{235}U(n,) reactions ( = 46), a cluster reaction with = 0 and a direct-interaction process with = 2. **3:**- We have gamma-ray production, and
*X*_{1}is the energy of the emitted photon in Mev. **5:**- This is an activation process,
*X*_{1}= 1000**Z*+*A*to identify the atomic number and mass number of the residual,*X*_{2}is the excitation level of the residual in Mev, and*X*_{3}is its halflife in seconds. **7:**- We have delayed fission groups, and
*X*_{1}is the halflife of this group. But if*X*_{1}= 0, then the data is a sum over all delayed groups. **8:**- This is a time-sequential cluster model, and
*X*_{1}gives the excitation level in Mev. **91:**- In this case
*X*_{1}designates the subshell.