1、C+ Program Structure (and tools),Today well talk generally about C+ development (plus a few platform specifics) Well develop, submit, and grade code in Windows Its also helpful to become familiar with Linux E.g., on shell.cec.wustl.edu For example, running code through two different compilers can ca
2、tch a lot more “easy to make” errors,Writing a C+ Program,C+ source files (ASCII text) .cpp,Programmer (you),emacs,editor,C+ header files (ASCII text) .h,1 source file = 1 compilation unit,Also: .C .cxx .cc,Also: .H .hxx .hpp,readme (ASCII text),Eclipse,Visual Studio,What Goes Into a C+ Program?,Dec
3、larations: data types, function signatures, classes Allows the compiler to check for type safety, correct syntax Usually kept in “header” (.h) files Included as needed by other files (to keep compiler happy)class Simple typedef unsigned int UINT32; public:Simple (int i); int usage (char * program_na
4、me);void print_i (); private: struct Point2D int i_; double x_; ; double y_;Definitions: static variable initialization, function implementation The part that turns into an executable program Usually kept in “source” (.cpp) filesvoid Simple:print_i () cout “i_ is ” i_ endl; Directives: tell compiler
5、 (or precompiler) to do something More on this later,A Very Simple C+ Program,#include / precompiler directiveusing namespace std; / compiler directive/ definition of function named “main” int main (int, char *) cout “hello, world!” endl;return 0; ,What is #include ?,#include tells the precompiler t
6、o include a file Usually, we include header files Contain declarations of structs, classes, functions Sometimes we include template definitions Varies from compiler to compiler Advanced topic well cover later in the semesteris the C+ label for a standard header file for input and output streams,What
7、 is using namespace std; ?,The using directive tells the compiler to include code from libraries that have separate namespaces Similar idea to “packages” in other languages C+ provides a namespace for its standard library Called the “standard namespace” (written as std) cout, cin, and cerr standard
8、iostreams, and much more Namespaces reduce collisions between symbols Rely on the : scoping operator to match symbols to them If another library with namespace mylib defined cout we could say std:cout vs. mylib:cout Can also apply using more selectively: E.g., just using std:cout,What is int main (i
9、nt, char*) . ?,Defines the main function of any C+ program Who calls main? The runtime environment, specifically a function often called something like crt0 or crtexe What about the stuff in parentheses? A list of types of the input arguments to function main With the function name, makes up its sig
10、nature Since this version of main ignores any inputs, we leave off names of the input variables, and only give their types What about the stuff in braces? Its the body of function main, its definition,Whats cout “hello, world!” endl; ?,Uses the standard output iostream, named cout For standard input
11、, use cin For standard error, use cerr is an operator for inserting into the stream A member operator of the ostream class Returns a reference to stream on which its called Can be applied repeatedly to references left-to-right “hello, world!” is a C-style string A 14-postion character array terminat
12、ed by 0 endl is an iostream manipulator Ends the line, by inserting end-of-line character(s) Also flushes the stream,What about return 0; ?,The main function should return an integer By convention it should return 0 for success And a non-zero value to indicate failure The program should not exit any
13、 other way Letting an exception propagate uncaught Dividing by zero Dereferencing a null pointer Accessing memory not owned by the program Indexing an array “out of range” can do this Dereferencing a “stray” pointer can do this,A Slightly Bigger C+ Program,#include using namespace std; int main (int
14、 argc, char * argv) for (int i = 0; i argc; +i)cout argvi endl;return 0; ,int argc, char * argv,A way to affect the programs behavior Carry parameters with which program was called Passed as parameters to main from crt0 Passed by value (well discuss what that means) argc An integer with the number o
15、f parameters (=1) argv An array of pointers to C-style character strings Its array-length is the value stored in argc The name of the program is kept in argv0,for (int i = 0; i argc; +i),Standard (basic) C+ for loop syntax Initialization statement done once at start of loop Test expression done befo
16、re running each time Expression to increment after running each time int i = 0 Declares integer i (scope is the loop itself) Initializes i to hold value 0 (not an assignment!) i argc Tests whether or not were still inside the array! Reading/writing memory we dont own can crash the program (if were r
17、eally lucky!) +i increments the array position (why prefix?),cout argvi endl;,Body of the for loop I strongly prefer to use braces with for, if, while, etc., even w/ single-statement body Avoids maintenance errors when adding/modifying code Ensures semantics/indentation say same thing argvi An examp
18、le of array indexing Specifies ith position from start of argv,Lifecycle of a C+ Program,C+ source code,Makefile,Programmer (you),object code (binary, one per compilation unit) .o,make,“make” utility,xterm,console/terminal/window,Runtime/utility libraries (binary) .lib .a .dll .so,gcc, etc.,compiler
19、,link,linker,E-mail,executable program,Eclipse,debugger,precompiler,compiler,link,turnin/checkin,An “IDE”,WebCAT,Visual Studio,window,compile,Development Environment Studio,Well follow a similar format most days in the course Around 30 minutes of lecture and discussion Then about 60 minutes of studi
20、o time Except for open studio/lab days, reviews before the midterm and final, and the day of the midterm itselfIn the studios, please work in groups of 2 or 3 Exercises are posted on the course web page Record your answers to the exercises, and e-mail your answers to the course account when youre done Well migrate throughout the studio to answer questionsUse studio time to develop skills and understanding A good chance to explore ideas you can use for the labs Exams will test understanding of the studio material Youre encouraged to try variations beyond the exercises,
