check sum

Description

Description: Most check digit schemes append an extra digit or digits, called the check digit(s), to the identification number and then use the digit(s) to check for errors after the number has been transmitted. To illustrate one possible method, consider the following scenario: A company uses a three-digit number a1a2a3 to identify each product it sells. To make sure these numbers are transmitted correctly, it adds a fourth digit (the check digit) a4; to each product number, creating the four-digit identification number a1a2a3a4. To do this, the first three digits of the number are added, a1+a2+a3, and the check digit a4 is assigned to be the last digit (the ones digit) of this sum. For product number 854, the check digit is 7 since it is the last digit in 8+5+4=17. The identification number is therefore 8547. The number 1090 would be a valid identification number, since the sum of the first three digits is 10 and the last digit of 10 equals the last digit (the check digit) of 1090. The number 7352 would be invalid, however, since the sum of the first three digits is 15 and 5, the last digit of 15 , does not equal 2, the last digit (the check digit) of 7352.

Your job is to write a program that can both generate and validate a checksum digit.

Requirements

• Given a list of numbers (three digits in length), generate a the checksum digit for each number and write the entire (4 digit) number to a file called "generatedValidCodes.txt ".

                e.g. 

                        the original list

                       456
                        754
                        345
                        945
                        123
                        856                         becomes: in the file "generatedValidCodes.txt"

                       4565
                        7546
                        3452
                        9458
                        1236
                        8569

• Given a list of 4 digit numbers, run through the list and find all the invalid ones. Write this list to a file called "InvalidCodes.txt" 
• The output file should contain the line number where the error occurred as well as the correct number it.       

                e.g.   
                        7546
                        3452
                        9454
                        1236
                        8562
                becomes: in the file "InvalidCodes.txt"

                         Line 3: value is 9454 but should be 9458
                         Line 5: value is 8562 but should be 8569                         

• This program must take user input from the command line prompt in the format of 

                            ./a.out <input.txt> <GENERATE||VALIDATE>

                            -Where ./a.out is the executable
                            - input.txt is a file containing the list of number to be checked
                            - GENERATE or VALIDATE is a flag specifying what we operation is to be performed on the input file

• If invalid input is given, the program must print an error and abort

  Additional/Optional Requirements Concepts

• Command line arguments
• File input/output
• File parsing
• Functions
• Looping constructs

Updated: August 31, 2005 08:28 AM