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Further Examples: ValueQ

At the start of a new session, no values have been defined for symbols such as xx.

In[1]:=

Out[1]=

This assigns the value to xx.

In[2]:=

Out[2]=

Now xx has a value.

In[3]:=

Out[3]=

This clears the value.

In[4]:= xx =.

Once again xx does not have a value.

In[5]:=

Out[5]=