C Calculator

Hi, this is a simple homework task that Im stuck on, can someone help me complete and comment out what they have done to the code to make it work? thanks! : The source file contains the basic structure of a simple command line calculator which will understand the following basic commands “add N”, “sub N”, “mul N”, “div N” and “exit”, where N is a floating point value. 4.1 Complete the while loop by adding character sequentially to the buffer. 4.2 Implement a check to ensure that you don’t write past the end of the buffers limits. Writing passed the end of an array is called an overflow. When an potential overflow is detected write an error message to stderr using fprintf and then call exit(1) to force the program to terminate early. 4.3 Ensure that once the while loop has exited the buffer is correctly terminated with the string termination character. 4.4 Use the strcmp function to test if the line reads “exit”. If it does, then readLine should return 0 otherwise it should return 1. Test the program. It should quit when a user enters “exit” otherwise it should print “Unknown command”. 4.5 Modify the while loop in the main function. Check that the line contains a three characters followed by a space. You can use the isalpha function from ‘ctype.h‘ to check that a character is a letter. If the line does not meet this criteria, then output an error “Incorrect command format” to stderr and use continue to begin the loop again. 4.6 Assuming the criteria for 4.5 is met then use sscanf to extract the 3 character command and the floating point value from the buffer to command and a respectively. Note: You will need to pass in_value to sscanf prefixed with the & operator. E.g sscanf(..., &in_value). This will be explained in the next lecture. 4.7 Modify the condition false to check the command to see if it is equal to “add” 4.8 Create an else if condition for sub, mul and div. Test your program. 4.9 Add additional conditions using strncmp to test the first two letter of the command. If it is “ad” then output “Did you mean add?” Complete cases for “su”, “mu”, “di”. Test your program.