According to student's score, program grades students from A to F along with their test score.

1. Input student's name
2. Record the student's score.
3. If there is other students to grade, input 'Y', otherwise, input 'N'.

This program stores student's information in the dictionary, key is their name and value is score. All the user's input is checked whether the answer is complying designed purpose. If a user input number when the name is required to be recoreded, then program will repeatedly ask to input number only. It prevents users from various potential errors. When the input is done, then program will compare each student's score with pre-determined standard. If a student's score is in range 'A' grade, then it will show 'A' for the student.