Here is a list of all documented files with brief descriptions:

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examples
C
filter_example.c	Example program for write then read of a variable using bzip2 compression
pres_temp_4D_rd.c	Example program for reading a 4D netCDF file
pres_temp_4D_wr.c
sfc_pres_temp_rd.c	A simple example of reading a netCDF file
sfc_pres_temp_wr.c	A simple example of writing a netCDF file
simple_nc4_rd.c	Read a simple file, with some of the features of netCDF-4
simple_nc4_wr.c	Write a file demonstrating some of the features of netCDF-4
simple_xy_nc4_rd.c	Read the simple_xy file, with some of the features of netCDF-4
simple_xy_nc4_wr.c	Write the simple_xy file, with some of the features of netCDF-4
simple_xy_rd.c	Write a file demonstrating some of the features of netCDF-4
simple_xy_wr.c	An example program demonstrating a simple 2D write
include
netcdf.h	Main header file for the C API
netcdf_filter.h
netcdf_mem.h	Main header file for in-memory (diskless) functionality
netcdf_par.h	Main header file for the Parallel C API
libdispatch
datt.c	These functions in this file rename and delete attributes
dattget.c	Attribute functions
dattinq.c	Attribute inquiry functions
dattput.c	Functions to write attributes
dcompound.c	Functions for Compound Types
dcopy.c	Copyright 2018 University Corporation for Atmospheric Research/Unidata
ddim.c	The functions in this file define, inquire about, and rename dimensions
denum.c	Functions for Enum Types
derror.c	Error messages and library version
dfile.c	File create and open functions
dfilter.c	Functions for working with filters
dgroup.c	Functions for netCDF-4 features
dopaque.c	Functions for Opaque Types
dparallel.c
dtype.c	Functions for User-Defined Types
dv2i.c	The V2 API Functions
dvar.c	Functions for defining and inquiring about variables
dvarget.c	Functions for getting data from variables
dvarinq.c	Functions for inquiring about variables
dvarput.c	Functions for writing data to variables
dvlen.c	Functions for VLEN Types
libhdf5
nc4hdf.c
nc4info.c
libnczarr
zarr.c
libsrc4
nc4attr.c
nc4cache.c	The netCDF-4 functions which control HDF5 caching
nc4dim.c
nc4dispatch.c
nc4grp.c
nc4internal.c
nc4type.c
nc4var.c
ncfunc.c