If you just have the a+b+c then you can get an error "Unrecognized command verb". Since its an expression, you have to assign it to something or put an = in front of it.

>Why can't I create the following string
>
>a='this'
>b='is'
>c='bob'
>
>
>a+b+c
>gives me errors
>
>
>d = a+b
>d = d+c
>works fine
>
>thanks in advance
>nick patel