To declare a variable, you need to know what data type it is going to be of and what its name would be. The variable name has constraints on what you can name it. Following are the rules for naming variables − Variable names in C++ can range from 1 to 255 characters. All variable names must begin with a letter of the alphabet or an underscore(_). After the first initial letter, variable names can also contain letters and numbers.   Variable names are case sensitive. No spaces or special characters are allowed. You cannot use a C++ keyword (a reserved word) as a variable name.Here ... Read More

To declare a variable, you need to know what data type it is going to be of and what its name would be. The variable name has constraints on what you can name it. Following are the rules for naming variables −Variable names in C++ can range from 1 to 255 characters.All variable names must begin with a letter of the alphabet or an underscore(_).After the first initial letter, variable names can also contain letters and numbers.  Variable names are case sensitive.No spaces or special characters are allowed.You cannot use a C++ keyword (reserved word) as a variable name.Here are ... Read More

Type inference or deduction refers to the automatic detection of the data type of an expression in a programming language. It is a feature present in some strongly statically typed languages. In C++, the auto keyword(added in C++ 11) is used for automatic type deduction. For example, you want to create an iterator to iterate over a vector, you can simply use auto for that purpose. Example#include #include using namespace std; int main() {    vector arr(10);    for(auto it = arr.begin(); it != arr.end(); it ++) {       cin >> *it;    }    return 0; }In the ... Read More

The auto and decltype serve different purposes so they don't map one-to-one. The auto is a keyword in C++11 and later that is used for automatic type deduction. The decltype type specifier yields the type of a specified expression. Unlike auto that deduces types based on values being assigned to the variable, decltype deduces the type from an expression passed to it. The value returned by decltype can directly be used to define another variable. The auto follows the rules of template parameter deduction. You can read more about these rule at Template Argument Deduction While decltype has rules it ... Read More

Auto is a keyword in C++11 and later that is used for automatic type deduction. Type inference or deduction refers to the automatic detection of the data type of an expression in a programming language. It is a feature present in some strongly statically typed languages. For example, you want to create an iterator to iterate over a vector, you can simply use auto for that purpose. example#include #include using namespace std; int main() {    vector arr(10);    for(auto it = arr.begin(); it != arr.end(); it ++) {       cin >> *it;    }    return 0; }In ... Read More

You can initialize a variable using the assignment operator or use its constructor when initializing it. For example,int i = 0; MyClass instance(1, "Hello");It will be automatically initialized ifIt's a class/struct instance in which the default constructor initializes all primitive types; like MyClass instance; You use array initializer syntax, e.g. int a[10] = {} (all zeroed) or int a[10] = {1,2}; (all zeroed except the first two items: a[0] == 1 and a[1] == 2) It is a global/extern variable It is defined static

Type inference (or type deduction) refers that the compiler can figure out the datatype of a variable or expression automatically, without the programmer needing to write it out. This feature is available in many strongly typed languages like C++, where the type system is strict but the compiler helps to reduce the typing effort. Following is the simple example to understand the type deduction in C++. #include using namespace std; int main() { // Let the compiler deduce the type from the value auto number = 50; // int auto pi = 3.14; // double cout

If you have statements like −Class Person;This is a forward declaration. It lets the following code know that there is are classes with the name Person. This satisfies the compiler when it sees these names used. Later the linker will find the definition of the classes.

In C++, declaration and definition are often confused. A declaration tells the compiler about the name and type, while a definition allocates memory or provides implementation. In this article, we will understand their differences with examples. What is a Declaration in C++? A declaration means (in C or C++) that you are telling the compiler about type, size and in case of function declaration, type and size of its parameters of any variable, or user-defined type or function in your program. No space is reserved in memory for any variable in case of the declaration. Following is the syntax to ... Read More

In C++, declaration and definition are often confused. A declaration means (in C) that you are telling the compiler about type, size and in case of function declaration, type and size of its parameters of any variable, or user-defined type or function in your program. No space is reserved in memory for any variable in case of a declaration.The Definition on the other hand means that in additions to all the things that declaration does, space is additionally reserved in memory. You can say "DEFINITION = DECLARATION + SPACE RESERVATION".Following are examples of declarations −extern int a;       ... Read More