>>I have to use character arrays instead of strings.
I must use the linear search

That pretty much precludes use of a map. It also means you can't use STL strings within a struct, and may preclude use of a vector to hold the structs, too.

You could use a C style string with either static or dynamic memory within the struct. The static version will limit the maximum length of any possible string entered, but since these strings will be words, then it would be unlikely that any given word would have more than 20 or 30 letters per word. Using dynamic memory to store the string within the struct will minimize the memory wasted by using strings of length less than than maximum length in the static version, but will require you to manage your own memory, which is a bit of a hassle, though not an overwhelming task by any means.

The non-STL structures you could use to store the structs could be either an array or a list. If you don't know the maximum number of possible unique words you could encounter then using a list might be advantageous. You could make a guess as to the max number of words, but that isn't quite as predictable as the maximum size of each word. Linear searching is possible with either lists or arrays.

Sorting the structures by string in alphabetical order before printing/sending values to file could be done in either of several different ways. For beginners, bubble sorts with arrays and insertion sorts with lists seem pretty popular.