I have the following program in Racket with the language set to "determine from source" and output syntax set to "write":
#lang r5rs
(define g '((w C C) (x A C) (y A B) (z B C)))
When I run it and type in the interactive prompt
> g
I get
{{w c c} {x a c} {y a b} {z b c}}
However, when I type the list directly to the prompt I get
> '((w C C) (x A C) (y A B) (z B C))
{{w C C} {x A C} {y A B} {z B C}}
How can I prevent Racket from turning the symbols to lowercase?
The R5RS standard requires the reader to hand symbols without case sensitivity. Most R5RS implementations will convert symbols with upper case symbols into lower case. If you need to produce a symbol with upper case letters, you need to use string->symbol.
> (string->symbol "Hello")
Hello
Since many Scheme implementations supported case sensitivity, later standards changed the default to case sensitivity.
See the (first!) question in the Scheme FAQ for a longer explanation: