• Introduction
• Software Conventions
  • Standard file structure
  • Header
    • Standard 2 lines header
    • Non standard header
  • Data line
    • Standard data line
    • Exceptions
  • Standard example with 3 column per data
• System and Fortran conventions
  • Fortran free format
  • Fortran fixed format
  • End of line
  • End of file
• Creating data files
  • Text editors
  • Spreadsheets
  • Word processor
• Revisions of this file

Introduction

This document describes a few common attributes of data files used by the program developed in Fortran and available on this site.

Software Conventions

These conventions result from choices made when developping the softwares.

• Standard file structure

  • Data files are ASCII (text) files. If prepared within a software other than a pure text editor, such as a word processor or a spreadsheet, they must be saved a text only files.
  • They are made of a header followed by data lines.

• Header

  • Standard 2 lines header

    The standard header is made of two lines:
    1. Title line: the first line contains the title
    2. Column headers line: the second line contains the columns headers
    The standard header is read in free format: title and column headers are character strings and need be delimited by single quotes ', so as to be read properly.

  • Non standard header

    • Files with other header settings can often be read by adjusting
      • the number of header lines to skip
      • the number of the line to read title from (0 if none)
      • the number of the line to read column headers from (0 if none)
      in the input module dialog.

• Data line

  Each data correspond to one line.

  • Standard data line

    • Data line are read in fortran free format.

  • Exceptions

    • Cases requiring fixed format: exact column location is required and there are no delimiters.

• Standard example with 2 reals, 1 integer, and 1 character string per data:

  1. 'Data title'
  2. 'Data_column1' 'Data_column2' 'Data_column3' 'Data_column4'
  3. 12000.6 2999.4567 245 'label_of_data1'

System and Fortran conventions

• Fortran free format

  • Reading rules:
    • Numerical data are separated by blanks or tabulations (more suited for spreadsheet)
    • Character strings MUST be delimited by quotes, ', to be read properly
    • If all the data to read within a line are found, the rest of the line is not read. This implies that extra information can be added AFTER the required data without affecting the input.
    • If all the data are not found within a line, the missing data will be sought in the next line. This implies that an incomplete line will be completed by the probably misinterpreted next line.
  • Possible file preparation:
    • in a text editor and saved as text only
    • in a spreadsheet and saved as text only (tab separated text output is most convenient)

• Fortran fixed format

  • Reading rules:
    • Numerical data and character strings are read within a specific column location.
      Column here means the number of characters (or spaces) counted from the beginning of the line
    • No delimiters are necessary: character strings are not delimited by quotes but by their column location
    • A column offset in the data file will result in misinterpreted data
  • Possible file preparation:
    • in a text editor and saved as text only; each character position must be counted from the beginning of each line.

• End of line

  Problems arise if the end of line is not consistent with the system used. Use text ftp transfert of data files between system as opposed to binary ftp transfer. Also note that MacOS.X (LF) end of line differs from that of MacOS.9 (CR): running native MacOS.X application requires data files with unix end of line (LF). Running MacOS.9 application under 'Classic' requires data files with MacOS.9 end of line (CR). A few text editors allow to easily check and modify end of line characteristics.

• End of file

  • Aways terminate the file with an empty line (extra line with no space). This avoids putting the end of file tag in a data line. In some systems such a situation can result in the last data line not being read 
  • Always check that the number of data stored in the program is exactly the expected number of data.

Creating data files

Data files can be created in a text editor or exported from a word processor or spreadsheet.

• Text editors

  End of line (MacOS9 (CR), Unix (LF), DOS (CRLF) ) can easily be checked and modified within the freeware TextWrangler, or the more complete BBEdit, (text encoding status is indicated and can be modified at the bottom of the window), or the freeware Smultron (menu text), or the shareware Plain Text Editor (menu edit).

• Spreadsheets

  The file can be made by saving a spreadsheet as tab delimited text. In that case, two pitfalls can be avoided by checking

  1. that the character strings are enclosed within quotes, and
  2. that the end of line is consistent with the system and application used (MacOS X applications require unix (not macintosh) end of line)

  A text editor can be used to substitute quoted characters for unquoted ones and verify end of line settings.

• Words processors

  The data file can be made by exporting as text. It is always a good idea to check that the end of line is consistent with the system and application used (MacOS X applications require unix (not macintosh) end of line). This may require using a text editor.

Revisions of this file

| 25-07-2003 | 01-03-2004 | 08-11-2004 | 30-11-2004 | 2007-11-21 | 2010-10-06 | 2022-09-02 |