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C++ Basics

Types

C++ is a statically typed language; type checking is done at compile time.


Type Meaning Minimum Size
bool boolean NA
char character 8 bits
wchar_t wide character 16 bits
char16_t Unicode character 16 bits
char32_t Unicode character 32 bits
short short integer 16 bits
int integer 16 bits
long long integer 32 bits
long long long integer 64 bits
float single-precision floating-point 6 significant digits
double double-precision floating-point 10 significant digits
long double extended-precision floating-point 10 significant digits

A char is guaranted to be big enough to hold a basic character, wchar_t, w_char16_t and char32_t are used for extended character sets (unicode). The remaining integral types represent integer values of (potentially) different sizes. Except for bool and the extended character types, the integral types may be signed or unsigned. A signed type represents negative or positive numbers; an unsigned type represents only values greather than or equal to zero. The types int, short, long, long long are signed, we obtain the corresponding unsigned type by adding unsigned to the type.

Type Aliases

A type alias is a name that is a synonym for another type. Type aliases let us simplify complicated type definitions, making those types easier to use.

typedef unsigned int size;
size border = 10;

size is a synonym for unsigned int

References

A reference defines an alternative name for an object. We define a reference type by writting a declaration of the form &d, wherer id is the name being declared.

#include <iostream>

int main()
{
  int number = 1024;
  int &reference = number;

  std::cout << reference << std::endl;
}

&reference refers to number

Pointers

A pointer is a compound type that “points to” another type. Like references, pointers are used fo inderect access to other objects. Unlike a reference, a pointer is an object in it’s own right. Pointers can be assigned and copied; a single pointer can point to several different objects over its lifetime. Unlike a reference, a pointer need not be initialized at the time is defined.

#include <iostream>

int main()
{
  int number = 1024;
  int *pointer = &number;

  std::cout << "pointer address:" << pointer << std::endl;
}

WARNING: The address stored in a pointer can be a null pointer.

Otherwise, we can use * to access that object.

#include <iostream>

int main()
{
  int number = 1024;
  int *pointer = &number;

  std::cout << "pointer value:" << *pointer << std::endl;
}

WARNING It is illegal to assign an int value to a pointer, even if the variable’s value happens to be 0.

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