typlen field in the pg_type table

For each table in my database, I am trying to extract the column name,
column type and column length from the system catalog tables.  I am able
to get the column name from the pg_attribute table and the column type
from the pg_type table.  However, I am having a problem extracting the
length of character columns from the typlen field of the pg_type table.

For example, I have a column defined as a char(20).  The column type is
set to "bpchar" but the typlen value for this column is -1.  The
documentation says that a value of -1 indicates "... has a length
word".  Can I extract the length of the field (in this case 20) from any
field in the system catalog tables?

In the documentation (Section 43.29) for the typlen field, it says "...
for a variable-length type, typlen is negative".  In Section 10.4, Item
3 says "... fixed-length type(e.g., char ...".  All of the char columns
in my database have typlen = -1.  IS A CHAR FIELD CONSIDERED A
FIXED-LENGTH OR VARIABLE-LENGTH TYPE BY POSTGRESQL?

Paul Tilles