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Reading/writing collection of records

Reading/writing collection of records

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  • 1. List different methods for record organization. Continue with the company class; Use fixed length of bytes , Use fixed number of fields Use length indicator, Use delimiter, Use index. Dr. Hussien M. Sharaf 2
  • 2. Dr. Hussien M. Sharaf 3 Fixed length of bytes Variable length Length indicator Record delimiter Record index Fixed number of fields
  • 3. A fixed length record file is one in which each record contains the same number of bytes. The length must be the max expected length. Problems: 1. The estimation of max length. 2. The choice of a character to fill the remaining space. 3. Not readable to human eye. 4. Waste of space. Dr. Hussien M. Sharaf 4 Record 3 Record 4Record 1 Record 2 200 bytes 200 bytes200 bytes 200 bytes
  • 4. A fixed number of fields where each field can be of variable size. The count must be the max expected count. Problems: 1. The estimation of max count. 2. Not readable to human eye. 3. Waste of space in case of an empty field. Dr. Hussien M. Sharaf 5 Record 3 Record 4Record 1 Record 2 180 bytes 190 bytes210 bytes 250 bytes 6 fields 6 fields6 fields 6 fields
  • 5. To choose a special character that will not appear within a record and then insert that after each record. Dr. Hussien M. Sharaf 6 3. Record Delimiter Problems: 1. The choice of a delimiter character that does not get in the way of processing (ex. White space is not a good choice cause the field may contain spaces within it like “address fields” same for @). Name EmailID Course Name EmailID Course Record1 Record2 n n
  • 6. Dr. Hussien M. Sharaf 7 4. Length indicator And 5. Index will be continued at next lecture
  • 7. 1. Start by determining Output. 2. List the inputs. 3. Think about processing.
  • 8. Continue using the CompanyInfo class: [A] Write a method that takes in ostream and writes to it a company record whose fields have Keyword = Value Write a driver to use this class based on the template Menu. Dr. Hussien M. Sharaf 9
  • 9. Continue using the CompanyInfo class: [B] Write a method that takes in istream and reads from it a company record whose fields have Keyword = Value Write a driver to use this class based on the template Menu. Dr. Hussien M. Sharaf 10
  • 10. Next week is the deadline. No excuses. Don’t wait until last day. I can help you to the highest limit within the next 3 days. Dr. Hussien M. Sharaf 11
  • 11. 1. Delete the “bin” and “obj” folders. 2. Compress the solution folder using winrar. 3. Rename the compressed file as follows: StudentName_ID_LecExcercise.rar 4. Email to: dr.sharaf@from-masr.com with your ID in the subject. Dr. Hussien M. Sharaf 12