Real programmers like line numbers. They were invaluable in identifying the source code line of syntax errors back when all the output came off the line printer.
:set number
For syntax highlighting the command is:
syntax on
Note: You may need to install the 'fanciest' versions of vi.
yum install vim-enhanced yum install vim-common
Sure. You can. But is it a good idea ? I have never seen a situation when it makes sense. If the code works, why mess with it. fortran is also a very portable language. standard compliant code from 30 years ago is still standard compliant code.