C++ Programming Using arrays

Project 5a8:

Write a program that will read a line of text and output a list of all
the letters that occur in the text together with the number of times
each letter occurs in the line. End the line with a period that serves
as a sentinel value. The letters should be listed in the following
order:the most frequently occurring letter, the next most frequently
occurring letter, and so forth. Use array with a struct type as its base
type so that each array element can hold both a letter and an integer.
You may assume that the input uses all lowercase letters. For example,
the input

Do be do be.

Should produce output similar to the following:

Letter Number of Occurences

O 3

d 2

b 2

e 1

Your program will need to sort the array according to the integer
members of the structs in the array. . The input/ output should be done
with the keyboard and screen & should be done with files.