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File Streams 03/04/11

Stream as Connection to I/O

Example of Creating a Stream  Program that outputs a quote to a file  writefile.cpp

To Connect Stream to File Header File #include Declare stream & open file ifstream fs_in(“mydata”, ios::in); ofstream fs_out(“myout”, ios::out);

To Connect Stream to File 3. Input/Output fs_in >> x; fs_out \n”; 4. Close fs_in.close( ); fs_out.close( );

Example of Input  Write a program to input a list of positive numbers from a file, then output the sum. –Create stream and connect to file. –Input number from input stream –While number not negative – Add number to sum – Input number from input stream –Output sum –Close stream streams4.2/sum.cpp

Another Problem Start Here  Write a program to input a file of five temperatures in degrees Celsius. Convert the temperatures to Fahrenheit and output them to another file. Use a function to do the conversion. What would the algorithm be? Let's write the program.(f = 9/5c + 32) celsius.txt

Sentinel Data in a File  Value that is not part of the data marks the end of a list.  I am going to use '*' as a sentinal to mark the end of data in some character input in the next example.

Caesar Cipher  Using the Caesar Shift (2 to the right), the message.  "RETURN TO ROME" would be encrypted as, "TGVWTP VQ TQOG"  Essentially, add +2 to the ascii value of a character.  To decode shift it back by -2

Caesar Cipher  When using cin with characters, spaces are skipped.  cin.get() inputs the spaces, too.

Caesar Cipher  Write a program that inputs a message from the keyboard and saves the coded version in a file called code.txt  Stop input when the sentinel, '*', is found.  cipher2.cpp uses a cin.get() so that spaces won't be skipped.

Exercise  p. 122, #2  Read sec. 7.3 for Friday.