C++ Notes
- -ToC
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- Basics -
- Introduction -
- Variables -
- Operators -
- Control Flow -
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Basics
-I. Introduction
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- A C++ program generally consists of preprocessor directives and the main function.
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- 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.
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- 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.
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II. Variables
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- 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.
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- Variables naming rules:
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- 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. -
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- Variable types: -
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- 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 -
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- Stores an indexable array of characters.
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- Stores an integer value of 0 or 1 representative of false or true respectively.
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- 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.
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int main() {
- int a; // Declaration
- a = 1; // Initialization
- int b = 2; // Declaration then initialization
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- 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.
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