Question

I am like 3 weeks new at writing c code, so I am a newbie just trying some examples from a Harvard course video hosted online. I am trying to write some code that will encrypt a file based on the keyword.

The point is each letter of the alphabet will be assigned a numerical value from 0 to 25, so ‘A’ and ‘a’ will be 0, and likewise ‘z’ and ‘Z’ will be 25. If the keyword is ‘abc’ for example, I need to be able to convert it to its numerical form which is ‘012’. The approach I am trying to take (having learned nothing yet about many c functions) is to assign the alphabet list in an array. I think in the lecture he hinted at a multidimensional array but not sure how to implement that. The problem is, if the alphabet is stored as an array then the letters will be the actual values of the array and I’d need to know how to search an array based on the value, which I don’t know how to do (so far I’ve just been returning values based on the index). I’d like some pseudo code help so I can figure this out. Thanks

Answer 1

In C, a char is an 8-bit integer, so, assuming your letters are in order, you can actually use the char value to get the index by using the first letter (a) as an offset:

char offset = 'a';
char value  = 'b';
int index = value - offset; /* index = 1 */