!!!Chapter 1 Getting Started
2012-08-28 07:46
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1.1Writing a Simple C++ Program
A function definition specifies four elements: return type, function name, parameter list and function body.Program files are referred to as source files, for example:
Prog.cc prog.cxx prog.cpp prog.cp prog.c
How to invoking MicroSoft compiler and running compiler from the command line:
1. Setting the Path and Environment Variables from command line
At the command prompt, change to the \bin subdirectory of your Visual C++ installation
c:\VS10\VC\bin>Run vcvars32.bat from command line
2. Write a .cpp program by notepad or something
3. In command line, go to the folder used to store the .cpp file and type:
cl -Ehsc abc.cppThis can generate abc.exe in the same folder
4. Run abc.exe directly and check the return value by the following command:
echo %ERRORLEVEL%
1.2 A First Look at Input/Output
Most of the input/output use iostream library.Standard Input and output objects:
cin: standard input
cout: standard output
cerr: standard error
clog: used to generate information
Preprocessor directive is used to tells the compiler that we want to use certain library. The name inside the angle bracket is a header. For example:
#include <iostream>Output operator (the << operator) writes its right-hand operand to the ostream that is its left-hand operand. For example:
Std::cout << "Enter two values:" << std::endl;Endl is a manipulator, when write to output stream, it can writing a newline to the output and flushing the buffer. By flushing the buffer, we ensure that the user will see the output written to the stream immediately.
Prefix std:: indicates the names cout and endl are defined in the namespace named std. Here :: is scope operator.
1.3 A Word about Comment
There are two kinds of comments in C++: single-line and paired.
A single-line comment starts with a double slash(//). For example:
// You can also put the comment before the code Std::cout << "hello"; // output some thing
A paired comment used /**/. It begins with a /* and end with the next */. Comment pairDo Not Nest
We can begin each line in the comment with an asterisk, and place a comment block above the code it explains. For example:
/* * This is comment */ Int main() { Return 0; }One way to ignore a section of code is to use your editor to insert single-line comment at the beginning of each line of code you want to ignore.
1.4 Control Structure
A condition is an expression that is evaluated so that its result can be tested. If the resulting value is nonzero, then the condition is true; if the value is zero then the condition is false.A block is a sequence of statements enclosed by curly braces. For example:
{ Sum+=val; ++val; }We could define variable inside the for statement:
for (int val=1;val<=10; ++val) { Sum+=val; }The scope of variables inside For-loop:
If we define the variable outside for-loop, we can still use the variable after the for-loop. And the value of the variable can be modified inside the for-loop
If we define the variable inside the for-loop, we will not be able to use the variable after the for-loop
Sample Code:
How to read unknown number of inputs:
#include <iostream> int main() { int sum=0, value; while(std::cin>>value) sum += value; std::cout <<"sum is:" << sum<<std::endl; return 0; }
line 5 will check if the input is still valid. An istream becomes invalid when we hit EOF or an invalid value. For example,if we input 1.2 it will show "sum is:1"!
1.5 Introducing Classes
In C++ we define our own data structure by defining a class.To use a class we need to know:
what is its name
where is it defined
what operations does it support
1.5.1 The sales_item Class
To use a class, we need not know anything about how it is implemented. Instead, what we need to know is what operations the class provides.When use a class, we must make the definitions associated with the class available to the compiler. Conventionally, class types are stored in a file with a name that, like the name of a program source file. The suffix is usually .h
Operations on Sales_item objects
Every class defines a type. The type name is the same as the name of the class.
We can define a variable of a class type:
Sales_item item1;Here item is an object of type Sales_item.
1.5.2 Member Functions
A member function is a function that is defined by a class. Member functions are sometimes referred to as the methodsof the class.Member functions are defined once for the class but are treated as members of each object.
When we call a member function, we specify the object on which the function will operate. This syntax uses thedot operator :
item1.same_isbnThe dot operator fetches its right-hand operand from its left. The dot operator applies only to objects of class type: The left-hand operand must be an object of class type; the right-hand operand must name a member of that type.
When we use a member function as the right-hand operand of the dot operator, we usually do so to call that function.
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