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C++ Interview Questions

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C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell Labs as an enhancement to the C language. Originally named C with Classes, the language was renamed C++ in 1983.

C++ is one of the most popular programming languages with application domains including systems software, application software, device drivers, embedded software, high-performance server and client applications, and entertainment software such as video games.

The language began as enhancements to C, first adding classes, then virtual functions, operator overloading, multiple inheritance, templates, and exception handling among other features. After years of development, the C++ programming language standard was ratified in 1998 as ISO/IEC 14882:1998. The standard was amended by the 2003 technical corrigendum, ISO/IEC 14882:2003. The current standard extending C++ with new features was ratified and published by ISO in September 2011 as ISO/IEC 14882:2011 (informally known as C++11)


auto: the default. Variables are automatically created and initialized when they are defined and are destroyed at the end of the block containing their definition. They are not visible outside that block

register: a type of auto variable. a suggestion to the compiler to use a CPU register for performance

static: a variable that is known only in the function that contains its definition but is never destroyed and retains its value between calls to that function. It exists from the time the program begins execution

extern: a static variable whose definition and placement is determined when all object and library modules are combined (linked) to form the executable code file. It can be visible outside the file where it is defined.

They are..


Const keyword indicates that memory once initialized, should not be altered by a program.

volatile keyword indicates that the value in the memory location can be altered even though nothing in the program
code modifies the contents. for example if you have a pointer to hardware location that contains the time, where hardware changes the value of this pointer variable and not the program. The intent of this keyword to improve the optimization ability of the compiler.   

mutable keyword indicates that particular member of a structure or class can be altered even if a particular structure variable, class, or class member function is constant.

struct data
char name[80];
mutable double salary;

const data MyStruct = { "Satish Shetty", 1000 }; //initlized by complier

strcpy ( MyStruct.name, "Shilpa Shetty"); // compiler error
MyStruct.salaray = 2000 ; // complier is happy allowed

reference is a name that acts as an alias, or alternative name, for a previously defined variable or an object.

prepending variable with "&" symbol makes it as reference.

for example:

int a;
int &b = a;

Method of passing arguments to a function which takes parameter of type reference.

for example:

void swap( int & x, int & y )
 int temp = x;
 x = y;
 y = temp;

int a=2, b=3;

swap( a, b );

Basically, inside the function there won't be any copy of the arguments "x" and "y" instead they refer to original variables a and b. so no extra memory needed to pass arguments and it is more efficient. 

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