About 17. That's when I got access to an IBM 704 or whatever. Fortran II, IIRC, Personal computers came a lot later. About 1976 or so. Assembler and BASIC (Palo Alto Tiny Basic)
I was probably eleven or twelve when I started playing around with a Commodore 64 and QuickBASIC. They were both old at the time, but they were from an era when computers were sold with the intent that the user would write their own software.