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C++ Articles
Page 285 of 597
Why does C++ require a cast for malloc() but C doesn't?
In C language, the void pointers are converted implicitly to the object pointer type. The function malloc() returns void * in C89 standard. In earlier versions of C, malloc() returns char *. In C++ language, by default malloc() returns int value. So, the pointers are converted to object pointers using explicit casting.The following is the syntax of allocating memory in C language.pointer_name = malloc(size);Here, pointer_name − Any name given to the pointer.size − Size of allocated memory in bytes.The following is an example of malloc() in C language.Example#include #include int main() { int n = 4, i, ...
Read MoreWhat is the difference between g++ and gcc?
g++GNU C++ Compiler ( g++ ) is a compiler in Linux which is used to compile C++ programs. It compiles both files with extension .c and .cpp as C++ files.The following is the compiler command to compile C++ program.g++ program.cpp -o filenameHere,filename − The name of file with .c or .cpp extension.The following is an example of using g++ compiler.Example#include using namespace std; int main() { int a = 20; cout
Read MoreWhat is the difference between an int and a long in C++?
intThe datatype int is used to store the integer values. It could be signed or unsigned. The datatype int is of 32-bit or 4 bytes. It requires less memory area than long to store a value. The keyword “int” is used to declare an integer variable.The following is the syntax of int datatype.int variable_name;Here,variable_name − The name of variable given by user.The following is an example of int datatype.Example#include using namespace std; int main() { int a = 8; int b = 10; int c = a+b; cout
Read MoreWhen to use references vs. pointers in C/C++
Reference variableReference variable is an alternate name of already existed variable. It cannot be changed to refer another variable and should be initialized at the time of declaration. It cannot be NULL. The operator ‘&’ is used to declare a reference variable.The following is the syntax of reference variable.datatype variable_name; // variable declaration datatype& refer_var = variable_name; // reference variableHere, datatype − The datatype of variable like int, char, float etc.variable_name − This is the name of variable given by user.refer_var − The name of reference variable.The following is an example of reference variable.Example#include using namespace std; int main() ...
Read MoreWhen should you use a class vs a struct in C++?
Structures and classes are very similar in C++ except for some differences. So details about these differences are given below that help to decide when to use a class or structure in C++.Differences between Class and StructureAll the members of a class are private by default. This is different compared to structures as all the members of a structure are public by default.A program that demonstrates a class in C++ is given as follows −Example#include using namespace std; class Example { int val; }; int main() { Example obj; obj.val = 20; return 0; }This ...
Read MorePrivate and Protected Members in C++
A class in C++ has public, private and protected sections which contain the corresponding class members.The private data members cannot be accessed from outside the class. They can only be accessed by class or friend functions. All the class members are private by default.The protected members in a class are similar to private members but they can be accessed by derived classes or child classes while private members cannot.A program that demonstrates private and protected members in a class is given as follows −Example#include using namespace std; class Base { public : int a = 8; ...
Read MoreWhen do function-level static variables get initialized in C/C++?
Static variables can be defined using the static keyword. They are variables that remain in memory while the program is running i.e. their lifetime is the entire program run. This is different than automatic variables as they remain in memory only when their function is running and are destroyed when the function is over.Function-level static variables are created and initialized the first time that they are used although the memory for then is allocated at program load time.A program that demonstrates function-level static variables in C is given as follows −Example#include int func() { static int num = 0; ...
Read MoreWhen to use new operator in C++ and when it should not be used?
Use of the new operator signifies a request for the memory allocation on the heap. If the sufficient memory is available, it initializes the memory and returns its address to the pointer variable.The new operator should only be used if the data object should remain in memory until delete is called. Otherwise if the new operator is not used, the object is automatically destroyed when it goes out of scope. In other words, the objects using new are cleaned up manually while other objects are automatically cleaned when they go out of scope.The following is the syntax of new operator.pointer_variable ...
Read MoreHow to return local array from a C++ function?
A local array cannot be directly returned from a C++ function as it may not exist in memory after the function call. A way to resolve this is to use a static array in the function. As the lifetime of the static array is the whole program, it can easily be returned from a C++ function without the above problem.A program that demonstrates this is given as follows.Example#include using namespace std; int *retArray() { static int arr[10]; for(int i = 0; i
Read MoreInitializing array with variable vs a real number in C++
An array is a collection of same type of elements at contiguous memory location. The lowest address in the array corresponds to the first element while highest address corresponds to the last element. The array index starts with zero(0) and ends with the size of array minus one(array size - 1).An array can be initialized with variables as well as real numbers. A program that demonstrates this is given as follows.Example#include using namespace std; int main() { int a = 5; int b = 3; int arr[4]; arr[0] = a; arr[1] = 8; arr[2] = b; arr[3] = 2; cout
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