Review of Strings which include file needs to be used for string manipulation? what using statement needs to be included for string manipulation? how is a string assigned a value? Can a string be initialized at declaration? how is getline() different from the extraction operator? what does this line do? string s1=”hi” + ’ ’ + ”there”; how are strings compared? Which one is greater? hell bell hello how can the size of a string be determined? Can string size be changed? What is the size of this string? string s2=”hello”; is there a problem with this statement? cout << s2[4]; assuming string s3=”C++ is fun”; what do the following functions do? s3.substr(4,2); s3.find(’+’); s3.rfind(’+’); s3.find_first_of(”is”); s3.find_last_of(”is”); s3.insert(3,2,’ ’); s3.replace(1,3,”--”); s3.append(”!!”); s3.erase(0,3);

Input/Output 2

Streams C++ uses streams for input and output stream - is a sequence of data to be read (input stream) or a sequence of data generated by the program to be output (output stream) by default only standard streams are declared: cin (console input) cout (console output) files are used to store information on permanent basis to do file input/output <fstream> needs to be included as well as using std::ifstream; and using std::ofstream; or using namespace std; an input or output stream needs to be declared: ifstream in_stream; // input stream ofstream out_stream; // output stream before C++ program can read from or write to a file stream, the stream needs to be connected to a file. This is referred to as opening the file: in_stream.open(”myfile.dat”); // opening file or combined: ifstream instream(“myfile.dat”); // Open myfile

Streams (Cont.) a string variable can be used as file name c_str() function has to be applied to the string: string filename=”myfile.dat”; instream.open(filename.c_str()); after stream variable has been connected to a file, extraction and insertion operators can be used with a stream: in_stream >> var1 >> var2 >> var3; after the file is opened all the operations on the file is done through associated stream before program finishes every stream needs to closed: in_stream.close(); // closing file one file cannot be opened for both reading and writing (even if two different streams are used) one file can be opened for reading, closed and then opened for writing or v.v. function eof() returns true if end of input file has been reached: while(!in_stream.eof()){ … }

I/O Error Checking function fail() returns true if previous stream operation failed Useful for checking reads and writes for problems, like data errors, end of data, formatting errors, etc. Can also be used to check whether an open operation succeeded before performing operations on the file. useful function exit() - exists program immediately. To use exit, include <cstdlib> exit() accepts one integer as argument: convention: 0 - normal program termination; nonzero - abnormal Example in_stream.open(”myfile.dat”); // opening file if (in_stream.fail()){ cout << ”Cannot open file myfile.dat”; exit(1); }

Streams as Parameters void myfunc(ifstream &myinfile); streams can be passed as parameters streams must be passed by reference void myfunc(ifstream &myinfile);