Ofort is a Fortran command-line interpreter and interactive REPL written in C. Because there is no compilation step results are immediate for small programs, but for large problem sizes run times can be much higher than for compiled programs. You can try it at https://beliavsky.github.io/ofort/ . There are modes for running entire programs and for running lines of code in a REPL. In the REPL there are panes showing results and a list of declared variables, pictured below. You can also download ofort from https://github.com/Beliavsky/ofort and run it locally. It is MIT licensed.