C++ Notes
ToC
Basics
I. Introduction
A C++ program generally consists of preprocessor directives and the main function.
A preprocessor directive tells the C++ preprocessor what to do before compiling. You can use this to include files, create macros, and determine compiling based on conditions. For example, include a file using #include This will include the iostream file from the C++ standard library.
The main function looks like:
int main() {
std::cout << "Hello world" << '\n';
return 0;
}int main() { is the declaration of the main function denoting it returns type int. return 0; is the return statement for the function. It is returning the integer 0. This tells the operating system, OK Quit the program safely.
II. Variables
A variable lets you allocate some memory in the computer and use it to store values. You can also recall the values for later. Variables contain a memory address and an identifier. An identifier can be *almost* anything you wish it to be.
Variables naming rules:
- Cannot start with a number.
- Can only contain alphanumeric characters and underscores.
- Cannot contain any reserved keywords (see here).
- If starting with an underscore, it can only start with one.
Variable types:
- Integers:
- short int:
- Size: 2 bytes.
- Range: -32,768 to 32,767
- int:
- Size: 4 bytes.
- Range: -2 billion to 2 billion
- short:
- Size: 8 bytes.
- Floats:
- float:
- Size: 4 bytes.
- 6 significant figures.
- double:
- Size: 8 bytes.
- 15 significant figures.
- long double:
- Size: 16 bytes.
- 19 significant figures.
- Character:
- Type: char Stores an integer value representative of an "ASCII" character.
- Size: 1 byte.
- String:
- Usage:
#include - Variable creation:
std::string identifier = "string literal"; - Boolean:
- Type: bool
- Size: 1 byte
-
Stores an indexable array of characters.
-
Stores an integer value of 0 or 1 representative of false or true respectively.
Variables are always declared before they are initialized. This means you must determine the type and the identifier before you store any values into it.
int main() {
int a; // Declaration
a = 1; // Initialization
int b = 2; // Declaration then initialization
}Constant types are variables identified by
const in their type definition. These are not allowed to be modified after they are declared and must be initialized at declaration.