A period is the number of generated steps a pseudorandom number generator (PRNG) takes before its output begins repeating. It reflects the cycle length of the generator’s mutating internal state. section 2.2.2
An LCG’s period
The implemented linear congruential generator uses a modulus of 2^31 − 1, multiplier 48271, and increment 0. Its period is 2^31 − 1: it starts repeating after 2,147,483,647 generated values. section 2.2.2
Figure 2.8 PRNGs have a state and are initialized with a seed. The PRNG algorithm keeps mutating the state.
Trace how a seed initializes PRNG state and how repeated algorithm steps mutate that state until the sequence cycles. section 2.2.2

