How does GDB debug fortran and print variables?

For details about how to debug fortran by GDB and how to print variables-general Linux technology-Linux technology and application information, see the following. After gfortran-g is run, generate the executable file, and then gdb Executable File
To print the value of variable
Print
No symbol "a" in current context prompt

One more question: I use two fortran files to generate an executable file. Both files have the variable,
How to only use variable a in watch file 1

Source program
Integer
A = 1
A = 2
A = 3
End
New hands GDB... hope you can guide me. Thank you ~ Merry Christmas ~