[corndoge]

Not sure if this is specifically related, but-

CTRL does not actually modify the character code sent from the keyboard. For letters, the same keycode (which maps to ASCII with a constant addition of 0x3D) is always sent. Another byte in the HID report contains bit flags for modifier keys (L/R CTRL, SHIFT, etc); the OS decides what happens after that.

Note that this holds under USB HID.

[jandrese]

Not on a modern PC, but on the machine ASCII was originally developed for I could definitely see the CTRL key just pulling one bit low on the keyboard encoder.