Used to general processes programmed by the user. A node of this type may be designed by any other letter different of G, L, I, D, E, R, C, A. The node is activated during scanning processes (this is the main difference with the A type). It has not EL or IL unless this is explicitly required by the user in a NODES declaration. The management of these lists must be programmed by the user with the help of GLIDER instructions and procedures.