i dont really see you making progress here, so have a look at this :
- set up a vector to save the users input
- have a do while loop set up to get the 100 inputs. exit this loop if the user types -1 or the 100 inputs are done
- sort the vector's entries
- size of the vector = number of grades
- for the average, just use a for loop to add all entries and then divide with the number of grades
- 1st entry is your minimum
- last entry is your maximum
- median = entry with the index size/2
- for the deviation use the formula provided in the task
how to find the median http://www.mathsisfun.com/median.html
Sort the values.
If there are an odd number of values, pick the middle one.
If there are an even number of values, pick the middle two, and take their average.