f_quickstart.f90 File Reference

Minimal introduction to NetCDF from Fortran - the simplest starting point. More...

Functions/Subroutines
program	f_quickstart
subroutine	check (status, context)
	Error handling subroutine.

Detailed Description

Minimal introduction to NetCDF from Fortran - the simplest starting point.

This is the most basic NetCDF example in Fortran, demonstrating the essential 6-step pattern:

1. Create file (nf90_create)
2. Define dimensions (nf90_def_dim)
3. Define variables (nf90_def_var)
4. Add attributes (nf90_put_att)
5. Write data (nf90_put_var)
6. Close file (nf90_close)

The program creates a tiny 2D array (2x3) with 6 integer values, adds descriptive attributes, writes it to a file, then reopens and reads the data back to verify the round-trip worked.

Learning Objectives:

• Understand the basic NetCDF workflow from Fortran
• Learn how to use the nf90_* API functions
• Master Fortran column-major array ordering
• Implement error handling with check() subroutine
• Verify data integrity

Key Concepts:

• Dimensions: Named axes that define array shapes (X=2, Y=3)
• Variables: Named data arrays with dimensions and types
• Attributes: Metadata describing the file or variables
• Define Mode: Phase where structure is defined (dimensions, variables, attributes)
• Data Mode: Phase where actual data is written/read
• Column-Major: Fortran arrays are stored column-first, opposite of C

Fortran vs C Differences:

• Array Declaration: Fortran data(X, Y) vs C data[X][Y]
• Array Indexing: Fortran 1-based (1 to N) vs C 0-based (0 to N-1)
• API Prefix: Fortran nf90_* vs C nc_*
• Module System: Fortran "use netcdf" vs C "#include <netcdf.h>"
• Error Handling: Fortran check() subroutine vs C ERR() macro

Prerequisites: Basic Fortran 90 programming knowledge

Related Examples:

• quickstart.c - C equivalent of this example
• f_simple_2D.f90 - More detailed 2D array example

Compilation:

gfortran -o f_quickstart f_quickstart.f90 -lnetcdff -lnetcdf

Usage:

./f_quickstart
ncdump f_quickstart.nc

Expected Output: Creates f_quickstart.nc containing:

• 2 dimensions: X(2), Y(3)
• 1 variable: data(X, Y) of type int
• 1 global attribute: description = "a quickstart example"
• 1 variable attribute: units = "m/s"
• Data: 6 sequential integers (1, 2, 3, 4, 5, 6)

Note

Companion code for "The NetCDF Developer's Handbook: The Authoritative Guide to Writing High-Performance Programs for Scientific Data Management, Second Edition" (https://www.amazon.com/dp/B0H7Q1Z75L)

Author

Edward Hartnett

Date

2026-01-29

Function/Subroutine Documentation

check()

subroutine f_quickstart::check	(	integer, intent(in)	status,
		character(len=*), intent(in)	context
	)

Error handling subroutine.

Parameters

status	NetCDF return status code
context	Descriptive message about the operation

f_quickstart()

program f_quickstart