These are Fortran programs that appear in my text

Elementary Numerical Analysis, 2nd edition, John Wiley, 1993.

The naming conventions are as follows.  In the name c3s1, the program
is from Chapter 3, Section 1.  In the name c3s3n1, the program is
from Chapter 3, Section 3; and it is the first program in the section,
with there being more than one.