Functions, Projects, and C++ I/O Streams

1. Functions, Projects, and C++ I/O Streams Dr. Nancy Warter-Perez June 4, 2003

2. Functions <return_type> func_name (arg1_typ arg1_name, …, argN_typ argN_name) { function body } • Func_name – name of the function • main – all programs must start with this function • Return_type – type of value returned by function • Arguments • call-by-value – arguments are inputs to function that can’t be modified by function • Function prototype (used in header files [*.h]) <return_type> func_name (arg1_typ, …, argN_typ); • Library functions – commonly used functions • iostream.h, string.h, stdlib.h, math.h (to name a few) Functions, Projects, and I/O Streams

3. Projects Separate Compilation Library functions *.a Compile Link File1.cpp Executable *.exe … Compile FileN.cpp Object files *.obj Functions, Projects, and I/O Streams

4. Steps to Creating a Visual C++ Project (Step 1) • To create a project • Under File, select New • Under Projects • Select Win32 Console Application • Assign a Project name and Location for your project • Select Create new workspace • When prompted for type of console application, select empty project • Click Finish • Click OK Functions, Projects, and I/O Streams

5. Steps to Creating a Visual C++ Project (Step 2) • To add a C or C++ source file to the project • Under File, select New • Under Files • Select C++ Source File • Select Add to project (Project will be set to the current project) • Assign a File name (use the default location determined by the project) • Click OK (the source file will be displayed in the editor window) Functions, Projects, and I/O Streams

6. Steps to Creating a Visual C++ Project (Step 3) • Enter your program in the editor • Notice that the editor has a color coding • Comments • Key words • Everything else • Also notice that it automatically indents • Don’t override!! • If doesn’t indent to proper location – indicates bug Functions, Projects, and I/O Streams

7. Steps to Creating a Visual C++ Project (Step 4) • To build your program • Under Build • Select Build project_name.exe • In case of compile time errors or warnings, they will be listed in the bottom window (scroll up) • Double click on error or warning to find in program • After fixing error (bug), rebuild following same steps Functions, Projects, and I/O Streams

8. Steps to Creating a Visual C++ Project (Step 5) • To execute your program • First, create any necessary input files • Under File, select New • Under Files, select Text File • Assign File name and Location (default ok) • It is OK to add to project (default) • Click OK • To run your program (can click ‘!’ icon, or) • Under Build, select Execute project_name.exe Functions, Projects, and I/O Streams

9. C++ I/O streams - input • Standard I/O input stream: cin • Ex: int x; char c1, c2, c3; cin >> x >> c1 >> c2 >> c3; If the following input is typed: 23 a b c Then, x = 23, c1 = 'a', c2 = 'b', c3 = 'c' (will ignore white spaces) Functions, Projects, and I/O Streams

10. C++ I/O streams - output • Standard I/O output stream: cout • Ex: int x = 454; char c1 = 'L'; cout << "Bioinformatics:\tCHEM " << x << c1 << endl; The following output is displayed: Bioinformatics: CHEM 454L Functions, Projects, and I/O Streams

11. I/O Streams Usage • Must include iostream header file • #include <iostream> • There are ways to format the output to specify parameters such as the width of a field, the precision, and the output data type Functions, Projects, and I/O Streams

12. File I/O – Fstream (1) • Preprocessor directive • #include <fstream> • Need a file object to keep track of file access information • fstream fin, fout; // can use any variable names • Need to open a file • fin.open("in_file.dat", ios::in); read-only • fout.open("out_file.dat", ios::out); write-only Functions, Projects, and I/O Streams

13. File I/O – Fstream (2) • To read from a file: • int x; fin >> x; //will read an integer value from in_file.dat into x • To write to a file: fout << x; • To close a file: • fin.close(); • fout.close(); • To detect the end of a file: • fin >> x; while (!fin.eof()) // eof will be set when end-of-file reached fin >> x; Functions, Projects, and I/O Streams