This code is a program that allows the user to create, display, update and delete student records. Each student record consists of four fields: first name, last name, course code and grade. The program uses a linked list data structure to store the student records in memory. The program defines a structure called student that contains the four fields and a pointer to the next student in the list. The program also defines a typedef for the structure called s. The program declares four global variables: head, tail, ptr and newstudent. Head points to the first student in the list, tail points to the last student in the list, ptr is used to traverse the list and newstudent is used to create a new student record. The program defines five functions: create, display, update, delete and main. The create function allocates memory for a new student record and prompts the user to enter the four fields. The function then adds the new student record to the end of the list. The display function prints all the student records in the list. The update function searches for a student record by first name and last name and allows the user to modify the course code and grade fields. The delete function searches for a student record by first name and last name and removes it from the list. The main function displays a menu with four options: 1.Create Student Record, 2.Display Student Record, 3.Update Student Record and 4.Delete Student Record. The function uses a switch statement to call the appropriate function based on the user's choice. The function uses a while loop to repeat the menu until the user exits the program.