more than one double quote problem

[webmasterpdx]

There is more than one type of double quote. I was experimenting with a program and I found that if I use double quotes generated by typing Alpha-0, I can use these for representing strings. However, if I use the double quotes from the Shift-9 selection menu, while these double quotes look identical to the previous ones on the screen, they are not accepted as string quotes, and I get a syntax error!!
Why did they do that? Why do they have 2 characters that appear identically on the display, not function the same? This seems moronic.
Enquiring minds want to know.