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C++学习笔记1

C++学习笔记1

作者: Yuu_0 | 来源:发表于2018-05-23 15:52 被阅读0次

    C++ Prime Plus

    Setting out to C++

    • C++ standard function header: int main() void mian();
    • Header Filenames: C++ header files have no .h extension. For example, the C++ version of math.h is the cmath header file;
    • Function form:
      Functions prototypes: void simon(int); double taxes(double); Function: void simon(int n) {...}; double taxes(double t) {...};

    Dealing with Data

    • Integer Types:
      A short integer is at least 16 bits wide;
      A int integer is at least as big as short;
      A long integer is at least 32 bits wide and at least as big as int;
      A long long integer is at least 64 bits wide and at least as big as long;
    • Some integer limits
    #include <iostream>
    #include <climits> // use limits.h for older systems
    int main()
    {
        using namespace std;
        int n_int = INT_MAX; // initialize n_int to max int value
        short n_short = SHRT_MAX; // symbols defined in climits file
        long n_long = LONG_MAX;
        long long n_llong = LLONG_MAX;
        // sizeof operator yields size of type or of variable
        cout << "int is " << sizeof(int) << " bytes." << endl;
        cout << "short is " << sizeof n_short << " bytes." << endl;
        cout << "long is " << sizeof n_long << " bytes." << endl;
        cout << "long long is " << sizeof n_llong << " bytes." << endl;
        cout << endl;
        cout << "Maximum values:" << endl;
        cout << "int: " << n_int << endl;
        cout << "short: " << n_short << endl;
        cout << "long: " << n_long << endl;
        cout << "long long: " << n_llong << endl << endl;
        cout << "Minimum int value = " << INT_MIN << endl;
        cout << "Bits per byte = " << CHAR_BIT << endl;
        cin.get();
        return 0;
    }
    

    Output:

    int is 4 bytes.
    short is 2 bytes.
    long is 4 bytes.
    long long is 8 bytes.

    Maximum values:
    int: 2147483647
    short: 32767
    long: 2147483647
    long long: 9223372036854775807

    Minimum int value = -2147483648
    Bits per byte = 8

    • Initialization with C++11
    int rheas = {12}; // set rheas to 12
    int emus{7}; // set emus to 7`
    int rocs = {}; // set rocs to 0`
    int psychics{}; // set psychics to 0
    
    • Display values in hex and octal
    #include <iostream>
    using namespace std;
    int main()
    {
    using namespace std;
    int chest = 42;
    int waist = 42;
    int inseam = 42;
    cout << "Monsieur cuts a striking figure!" << endl;
    cout << "chest = " << chest << " (decimal for 42)" << endl;
    cout << hex; // manipulator for changing number base
    cout << "waist = " << waist << " (hexadecimal for 42)" << endl;
    cout << oct; // manipulator for changing number base
    cout << "inseam = " << inseam << " (octal for 42)" << endl;
    return 0;
    }
    
    • C++ Escape Sequence Codes
    Character Name ASCII Symbol C++ Code
    Newline NL \n
    Horizontal tab HT \t
    Vertical tab VT \v
    Backspace BS \b
    Carriage return CR \r
    Alert BEL \a
    Backslash \ \\
    Question mark ? \?
    Single quote ' \'
    Double quote '' \''
    • The const Qualifier
      The general form for creating a constant is this: const type name = value;
      If your background is in C,you might feel that the #define statement,which is discussed earlier,already does the job adequately. But const is better. For one thing, it lets you specify the type explicitly. Second, you can use C++’s scoping rules to limit the definition to particular functions or files. Third, you can use const with more elaborate types, such as arrays and structures.

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