File management, reading and writing strings/numbers into disk

2. Introduction to file organization:
◦ What? Why? How?
File organization challenge
History of File organization
Streams operations
Dr. Hussien M. Sharaf 2

3. Dr. Hussien M. Sharaf 3
File organization : is rearranging data
structures and its operations in order to
enhance performance of data reading and
writing from and to secondary storage media
(disks).

4. Dr. Hussien M. Sharaf 4
Data structures
RAM/Main memory
Operations for
accessing data
File structures File processing
Secondary memory
(Disks)

5. Dr. Hussien M. Sharaf 5
File structures: is organization of data
representation on secondary devices such as
disks.
File processing (Streams Operations): The
processing (treatment) of data on secondary
devices such as disks. It involves transferring
data between secondary devices and RAM.
This will be built based on your knowledge of
Data Structures.

6. The study of file
organization and
processing is needed in
order to retrieve data from
secondary storage into
RAM so that programs can
process them.
The retrieval process must
be as fast as possible.
Dr. Hussien M. Sharaf 6

7. 1. Minimize number of trips to the disk in
order to get desired information.
2. Grouping related information so that we
are likely to get everything we need with
only one trip to the disk (e.g. name, address,
phone number, account balance).
Dr. Hussien M. Sharaf 7

8. Dr. Hussien M. Sharaf 8

9. Dr. Hussien M. Sharaf 9

10. Reading/writing data is slow (since
electronic and mechanical)
Dr. Hussien M. Sharaf 10

11. Dr. Hussien M. Sharaf 11

12. Dr. Hussien M. Sharaf 12

13. ofstream: Stream class to write on files
ifstream: Stream class to read from files
fstream: Stream class to both read and
write from/to files.
Dr. Hussien M. Sharaf 13

14. ios::in Open for input operations.
ios::out Open for output operations.
ios::binary Open in binary mode.
ios::ate
Set the initial position at the end of the file.
If this flag is not set to any value, the initial position is the
beginning of the file.
ios::app
All output operations are performed at the end of the file,
appending the content to the current content of the file. This
flag can only be used in streams open for output-only
operations.
ios::trunc
If the file opened for output operations already existed
before, its previous content is deleted and replaced by the
new one.
Dr. Hussien M. Sharaf 14

15. ofstream myfile;
myfile.open ("example.bin", ios::out |
ios::app | ios::binary);
Dr. Hussien M. Sharaf 15
class default mode parameter
ofstream ios::out
ifstream ios::in
fstream ios::in | ios::out
ofstream myfile ("example.bin", ios::out |
ios::app | ios::binary);

16. Dr. Hussien M. Sharaf 16
if (myfile.is_open())
myfile << "This is a line.n";
myfile.close();
Check that the stream is
opened.
Write data into stream.
Close the stream and
hence the modifications are
saved into the file.

17. tellg() and tellp()
These two member functions return an integer
representing the current position of the get stream
pointer (in the case of tellg) or the put stream pointer
(in the case of tellp).
seekg(count, offset) and seekp(offset, direction)
These functions allow programmers to change the
position of the get and put stream pointers.
ios::beg offset counted from the beginning of the stream
ios::cur offset counted from the current position of the stream pointer
ios::end offset counted from the end of the stream

18. Dr. Hussien M. Sharaf 18
What does this program do?
- Obtain the size of a file

19. Check Examples 2.1 and 2.2
Write a program that generates a random array of 12
integers and then write each element into a new line in a
file “ArrayElem.txt”.
Send the source code project (after zipping it) to my email:
n.abdelhameed@fci-cu.edu.eg
Follow instructions made in the last page. Make sure to
send your ID. Students who don’t send their IDs clearly
will loose marks.
Dr. Hussien M. Sharaf 19

20. Check Examples 2.1 and 2.2 using VS2008 or VS2010
Write a program that reads a given number of lines from
“ArrayElem.txt” and displays them into one line
separated by comma “,”.
Send the source code project (after zipping it) to my email:
n.abdelhameed@fci-cu.edu.eg
Follow instructions made in the last page. Make sure to
send your ID. Students who don’t send their IDs clearly
will loose marks.
Dr. Hussien M. Sharaf 20

21. 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 21

22. 1. Delete the “bin” and “obj” folders.
2. Compress the solution folder using
winrar.
3. Rename the compressed file as follows:
StudentName_ID_A1.rar
StudentName_ID_A2.rar
4. Email to: n.abdelhameed@fci-cu.edu.eg
with your ID in the subject.
Dr. Hussien M. Sharaf 22