A simple loop that reads the next word, finds it in the dictionary and executes its associated code. A word starts with any character and ends at the first special character.
Words have arbitrary length.
The leading characters are stored in the dictionary and the rest discarded. The convention the words may start with special characters increases the set of words with mnemonic value. The scanner depends upon a character pointer to tell it where to read next. A word may change this pointer and thus alter the sequence of input words. This is the way definitions and backward branches are implemented.