Hello, I need to solve a character puzzle on c.

I need to convert the character array:

"abcdefghijk"

to

"ABENTEUEROnullnullnull"

For example the first 2 characters would be done like this:

chararray[0] - ' ' ; would convert a -> A

chararray[1] - ' '; would convert b -> B

So far i can see that the 'c' would be:

chararray[2] - 'RS'; (record seperator) but does not work...

Help would be appreacited, thanks! ALSO, it must be done by taking a value (- minus)!