The inputs to the combinational logic are the system inputs and the
contents of memory; the combinational logic outputs are the system outputs
and signals to update the memory.
In Section 6.2, we will introduce the simplest storage device, the
latch. It is a static device constructed of gates. The output changes
immediately whenever the input changes; there is no clock involved.
Latches are used primarily for temporary (buffer) storage.
In Section 6.3, we will develop the most common binary storage
device, the flip flop. A flip flop almost always has two outputs, q and q;
that is, both the bit stored and its complement. It may have one or two
inputs (indeed, they used to make one with three); we will describe several
types of flip flops.
In Section 6.1, we will introduce state table, state diagrams, and
timing traces. In Section 6.4, we will discuss the analysis of sequential
systems.