Presentation is loading. Please wait.

Presentation is loading. Please wait.

Review of Strings which include file needs to be used for string manipulation? what using statement needs to be included fro string manipulation? how is.

Similar presentations


Presentation on theme: "Review of Strings which include file needs to be used for string manipulation? what using statement needs to be included fro string manipulation? how is."— Presentation transcript:

1 Review of Strings which include file needs to be used for string manipulation? what using statement needs to be included fro string manipulation? how is a string assigned a value? Can a string be initialized at declaration? how is getline() different from 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);

2 Input/Output

3 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; an input or output stream needs to be declared: ifstream fin; // input stream ofstream fout; // 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: fin.open(”myfile.dat”); // opening file

4 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”; fin.open(filename.c_str()); after stream variable has been connected to a file, extraction and insertion operators can be used with a stream: fin >> 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: fin.close(); // closing file function eof() returns true if end of input file has been reached: while(!fin.eof()){ … }

5 I/O Error Checking function fail() returns true if previous stream operation failed useful to check if file is opened successfully before performing operations on 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 fin.open(”myfile.dat”); // opening file if (fin.fail()){ cout << ”Cannot open file myfile.dat”; exit(1); }

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


Download ppt "Review of Strings which include file needs to be used for string manipulation? what using statement needs to be included fro string manipulation? how is."

Similar presentations


Ads by Google