C + + Interview Basics

1.Static

Staic Features: Only initialized once, there is a static zone, different from the auto variable, there is Yu Ching (function end, also destroyed).

Staic within a class: static data members must be initialized outside the class, static member functions can only call static variables, neither can be called with the this pointer.

2.Const

const int *a== int const* A A variable, a pointed object is not mutable

int* Const A:A Immutable, pointing to object variable

3.Switch

If the switch break is not written, it will be executed on the statement that satisfies the condition, until break, or the function ends;

4. Why:

Char str1*= "ABC";

Char str*2= "ABC";

STR1==STR2 established? ABC is stored in a constant area, and most compilers keep only 1 copies of the same constants, so str1 and str2 point to the same address.

5.Assert

The difference between assert and assert: The former is in the debug version, the relase version does not exist, and the assert will exist;

#define NDEBUG can prohibit calling macros;

6.enum

Enum (a,b=1,c,d=2,e) = = 0,1,2,2,3

7.ARGC and argv[]

(test.c) int main (int argc,int*argv[]) {...}

Command line input: Hong bi yue I

Argv[]=[test, Hong,bi,yue,i];

argc=5;

After the 8.main function is finished

After the main function finishes, if you want to continue executing the code, you can then perform the destructor

9.++

A.

*p++: *p-p++ address plus;

(*p) + +: (*p) + + value plus;

B.

S++=5: Error, first executes the address of a, mount the register, and then the temporary variable is the value of a plus 1, the program does not allow the assignment of temporary variables;

++s=5: Correct, take a address, content +1, put register;

10. Notes on floating-point numbers:

float A,b,c;

1.if (a==0): Floating point number has a precision problem, not an exact value, need to convert to: >= or <=;

2. A+b=b+a;

(a+b) +c is not necessarily equal to: (a+c) +b floating-point operations can not be combined------------??? Don't understand

The 11.String class implements the point of note:

1.String:: String (const string &another)

{

char* m_data; To invoke the strcpy () function, use the pointer

m_data= New Char[strlen (another.m_data)+1]

strcpy (M.data,another.m_data);

}

12.extern and Export

Note: The general definition of a variable in the header file will cause a duplicate definition, that is, using the #ifdef, although the header file is only compiled once, but the variable is not only defined once;

Extren int n;

Export Template<class t> void f (t& T);

13 Memory allocation

(1) symbol start block (BSS): Static data + uninitialized global data

(2) Data segment: Static memory allocation, initialized global data

(3) Code snippet: Program execution code

(4) Heap: Dynamically allocated Memory: malloc and new

(5) Stack: Temporary creation of local variables

C + + Interview Basics