A Free-Format Data Input Scheme Written in Standard FORTRAN (ANSI 66)

The 1966 ANSI standard FORTRAN specifies the input of numerical data only in fixed format. Described here is a scheme, written in ANSI 66 FORTRAN, which allows numerical data prepared in accordance with the FORTRAN 77 free-format specification to be read. In addition, the scheme is designed so that ill-formed or ambiguous data are given a reasonable interpretation and the location of the suspect data and the value assumed are identified. 1. Introduction Programs written in standard FORTRAN IV are limited to data input with fixed format. Often it is more convenient to input data separated by commas or spaces and, in recognition of this, various manufacturers have introduced their own free-format data input routines. Unfortunately, these are not standard and programs and data prepared for input in free-format on one manufacturer's machine cannot, in general, be transferred to those of another manufacturer. In this paper, free-format data input routines, written in standard ANSI 66 FORTRAN (ANSI, 1966) are presented. The scheme enables data to be read into various arrangements of variables, with each routine starting to read on a new line of data and continuing until either a specified number of numbers has been read or an end of read symbol (/ or $) is encountered. In specifying the routines, the aim has been to give the correct interpretation of all well-formed numbers and, when ambiguous data are encountered, to give a reasonable interpretation and to issue a warning. A failure in the input routines can only occur from a system failure, for example if a number is too large for the computer to handle or an attempt is made to read beyond the end of a file. No 'end of file' detection facility exists in standard FORTRAN, hence this facility of FORTRAN 77 and many non-standard implementations cannot be used in standard FORTRAN 66. Whilst one of the aims in the specification of the routines has been to maintain compatibility with existing formated data for FORTRAN programs, this has not always been possible. For example, in order to read the two numbers 149 and 736 in FORTRAN 213 format, they would appear in the data as 149736. The input scheme described here would interpret this as the single number 149736. For all cases where formated data are separated by a non-digit character, the routines will read in the numbers as intended. In addition, the routines will interpret correctly …