Develop a program interpreter in C++ following this grammar:

-> start stop

-> ; { }

- > = | input | show | show "string" | show ' ' | int

-> { }

-> "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" | "J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" | "S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z"

The program should allow the user to enter the file name of the source code and detect errors, and run the program if there is no grammar error.