I MATRIX VOLTS PIBY4 OLDCHI TWOX R2D2 OUTPUTAnd here are some names which do not conform to the rules:
|(too many letters)
|(underscore is not allowed)
|(starts with a digit)
|(lower-case letters are not allowed).
The six-character limit on the length of a symbolic name is one of the most unsatisfactory features of Fortran: programs are much harder to understand if the names are cryptic acronyms or abbreviations, but with only six characters there is little choice. Although many systems do not enforce the limit (and Fortran90 allows names up to 31 characters long), at present the only way to ensure software portability is to keep to it strictly. There is a further problem with items which have an associated data type (constants, variables, arrays, and functions). Unless the data type is declared explicitly in a type statement, it is determined by the initial letter of the name. This may further restrict the choice.