14.1.3 Compiler Options

g77 offers compiler options that f2c doesn't, most of which are designed to more easily accommodate legacy code:

• Two that control the automatic appending of extra underscores to external names
• One that allows dollar signs (`$') in symbol names
• A variety that control acceptance of various “ugly” constructs
• Several that specify acceptable use of upper and lower case in the source code
• Many that enable, disable, delete, or hide groups of intrinsics
• One to specify the length of fixed-form source lines (normally 72)
• One to specify the the source code is written in Fortran-90-style free-form

However, f2c offers a few that g77 doesn't, like an option to have REAL default to REAL*8. It is expected that g77 will offer all of the missing options pertinent to being a Fortran compiler at some time in the future.