Credit Card Number Validator

Table of Contents

• Requirements
• Design
• Test Scenarios
• Implementation
• Successes and Failures
• Source Code
  

Requirements

• Input
  • string to verify if it is a valid credit card number
    
• Output
  • the credit card number string inputed and the result of whether or not it is valid
    
• Constraints
  • must be able to validate any 16 digit credit card number using the luhn method
    
  • program format per CS225 style requirements 1-6
• User interface
  • console based
    
• Extra credit
  • none

Design

• Input:
• string to verify if it is a valid credit card number
• Output:
• the credit card number string inputed and the result of whether or not it is valid
• Components:
  • User interface (in main because it was quick and professor didn't require seperate UI function for this assignment)
  • Credit Card Number Validator fucntion
  • Support functions
  • Remove Whitespace
• Departures from requirements:
  • none
    

Test scenarios

• input empty;
  creditcard should be reported as invalid
• input is of improper length;
  creditcard should be reported as invalid
• input digits are of non integer type;
  creditcard should be reported as invalid
• input contains whitespace;
  creditcard should be validated without those spaces
  
• input is valid creditcard number;
  output should show the creditcard number and then show if it was valid or not
• input is all zeros;
  this is a valid according to the luhn method, so it should work as other valid creditcards

Implementation

• Implementation Design
• main()
• get user input
• send user input to checkCC()
• if user input equals true
• print input
• print that it is a valid creditcard
• else
• print input
• print that it is not a valid creditcard
  
• checkCC()
• call removeSpaces() to remove spaces from input
• check to see if input is 16 characters in length
• if not 16 characters in length set retVal to false
• check to see if input contains only numeric digits
• if not set retVal to false
• starting with the 2nd to last digit in the input
• times digit by 2
• convert result to string with itos()
  
• and insert it in the current place (shifting anything to the right as needed) in the input
• move over two digits tp the left and repeat until we can't move anymore digits to the left
• itterate through each digit of the result
• call atoi() to convert it to an integer
• add it in to the sum (starts at zero)
• divide sum by 10
• if remainder is zero, then set retVal to true
  
• removeSpaces()
• return a string with any spaces removed
  
• itos()
• return a string representation of an integer
  
• Implementation test scenarios
  • main()
    
    • ensure that proper result from checkCC is printed to screen
      
  • checkCC()
  • ensure that the values of the parameters are the same as their corresponding variables in GravityUI()
  • removeSpaces()
  • ensure that all spaces have been removed and only spaces have been removed
    
  • itos()
  • esure that the function works like itoa(), at least enough to work in this program like itoa() did, but returning a string instead of a char*
    
• Code:
  
• See Source Code.

Successes and failures

• Everything worked when compiled on Visual Studio 2005 C++ Express, but apparently itoa() is not standard so the version of g++ on linux I tried failed. So a simple function was created in order eliminate uses of itoa() in the code.
  
• Code will print non visible characters if inputed (in linux), this should be fixed.