Getting Started with C + + Basics: Classes and references

I. Classes (6 default functions of a Class), objects, object-oriented concepts

1.cpp data type (except for C)

Basic data type: BOOL type logic non-basic type: Class

Non-type void type

"1" namespace (in order to resolve the problem of global variable naming conflicts)

Example: #include <iostream.h>

using namespace Std; Standard input-output stream, namespace Std

int main ()

{

cout<< ' Hello World ' <<Endl; Cout and Endl are objects, from namespaces, written as:std::cout<< "Hello World" if the namespace is not previously declared <<std::endl;

System ("pause");

return 0;

}

You can add definitions to the namespace at any time, but all are defined in the same namespace

Example: #inlcude <iostream.h>

Namespace Bit1//define a namespace

{

int a=0;

}

namespace Bit2//defining another namespace

{

int a=20;

}

int main ()

{

bit1::a=30; :: For Scope resolver

Bit2::a=40

}

2. Input/output stream

cout→ standard output Stream object,<< output operator;

cin→ standard input Stream object,>> input operator;

endl→ standard line break operator;

3. Function overloading

Example: #include <iostream.h>

using namespace Std;

int add (int num1,int num2)

{

return num1+num2;

}

Float (float f1,float F2)

{

return F1+F2;

}

int main ()

{

int num1=0;

int num2=0;

float f1=0.0;

float f2=0.0;

cin>>num1>>num2;

int Ret=add (NUM1,NUM2);

cout<< "ret=" <<ret<<endl;

cin>>f1>>f2;

Float F3=add (F1,F2);

}

Note: "1" is within the same scope, a set of function names is the same, the parameter list < number/type is different > different, the return value type can be different.

When the "2" determines whether a function is overloaded, it is only necessary to determine whether its functions and parameter lists are the same.

"3" in C and CPP, the rules of function overloading are different, so use the C function in CPP with extern "C".

4. Default function

"1" Full default function

Example: int add1 (int a,int b)

{

return a+b;

}

int main ()

{

int ret=add1 (); There is no need to write a parameter here, if you change it to ADD1 (3), the result is 3, because the parameter is filled from left to right

return 0;

}

"2" semi-default function

Example: int add2 (int a,int b=0)

Two. Pointers and references

Reference: "1" does not define a new variable, but instead assigns a new name to a variable that is already defined, and the variable can be referenced multiple times, that is, a variable can have multiple aliases;

"2" reference to be initialized, to identify who is whose alias;

"3" references can be passed, such as &q=m;&r=q;

"4" an alias can reference only one variable

1.const references

Example: #include <iostream.h>

using namespace Std;

int main ()

{

int *q=null;

const int *P=Q;

int m=10;

const INT &n=m; Often referenced, at this time n as a constant treatment, can not directly modify N, only by modifying m to modify

return 0;

}

Note: "1" Cannot assign a const-modified variable to a variable that is not const-modified

"2" cannot refer to a constant directly unless you add a const, such as a const int &r=5

Example: Double b=3.14;

const INT &k=b;

"3" in the execution of the code, intermediate variables < temporary > is a constant attribute, you have to use const to decorate.

2. References are used in function parameters

Example: #include <iostream.h>

using namespace Std;

int swap (int *a,int *b)//pass pointer to exchange values of two variables

{

int tmp=*a;

int *a=*b;

*b=tmp;

}

For the swap function, there is another way to use the reference

Example: void swap (int &a,int &b)

{

int tmp=a;

A=b;

b=tmp;

}

int main ()

{

int a=10;

int b=20;

Swap (A, b);

return 0;

}

3. Refer to the arguments frequently (when you do not want the value of the parameter x to be changed within the function)

Example: void Readbigdata (const bigdata &x)

{

int a=x.arr[1000];

}

Note: When you return a value as a reference, you cannot reference a temporary variable

Example: int fun ()

{

int ret=10;

return ret; This returns a temporary variable, preferably not written like this.

}

4. Value return and reference disassembly

"1" Value returns: Place the value in the RET in the EAX register

Assembly language: Mov Eax,dword Ptr[ret];

"2" Reference disassembly: Place the address of the RET in the eax, like a pointer

Assembly language: Lea Eax,[ret];

Example: #include <iostream.h>

using namespace Std;

①int Add (int a,int b)

{

int ret=a+b;

return ret;

}

② int *add ()

{

int ret=a+b;

Return &ret;

}

③int &add (int a,int b)

{

int ret=a+b;

return ret;

}

The functions of the above three add functions are the same.

References and pointers differ and relate to:

1. The reference can only start when initialized once, can not point to other variables;

2. The reference must point to a valid variable, and the pointer can be empty;

The 3.sizeof reference refers to the size of the reference object, and the sizeof pointer refers to the size of the object address;

4. The meaning of the self-increment or decrement of the pointer and the reference is not the same;

5. Reference is more secure than a pointer;

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Getting Started with C + + Basics: Classes and references