Start Programming in C++

Before continuing, make sure you have installed the required software in Getting Started - Software Setup.

In this guide, you will learn:

1. How to use the command-line interface.
2. How to compile C++ programs.
3. How to run your compiled programs.

The Command-Line Interface (CLI)

Demonstration on how to get up and running with the command line to compile and run C++ programs.

• Powerful method of interacting with the computer
• Accepts successive lines of typed commands (instructions)
• Commands may print (display) text output.

Accessing the CLI

OS	Name	Icon
Windows	“Command Prompt” or “CMD”
macOS	“Terminal”
Linux	“Terminal,” “Shell,” or similar

Example Commands

Windows	macOS / Linux	Description
cd	cd	Change directory
dir	ls	List directory
copy	cp	Copy a file or directory
move	mv	Move a file or directory (also useful to rename files)
del	rm	Remove a file or directory
mkdir	mkdir	Make a new directory
cls	clear	Clear the CLI

Parameters

• A parameter is an additional piece of information passed to the command.
• Parameters are space separated
• Examples (in Windows)
  • dir /?
    • Displays helpful information about the dir command including what additional parameters do.
  • dir /w /p
    • Displays a list of files and subdirectories in a directory in a wide list view and pauses after each screenful of information.

Compiling with GCC

Before continuing, you should have Visual Studio Code and g++ to make your first C++ program. Refer back to Getting Started if needed.

A Simple C++ Program

• Create a text file named hello.cpp (cpp is the extension we give to C++ source code files).

• Type the following code into the file (displays “Hello World!” on the screen).

  #include <iostream>
  using namespace std;
  
  int main()
  {
  	cout << "Hello World!" << endl;
  
  	return 0;
  }

Compiling with g++

In the command-line interface:

• Change the directory to the location of hello.cpp.
  • For example, cd "C:\Users\Sean\235"
  • Hint: Put double quotes around any parameters with spaces.
  • Hint: Hit tab while typing the path to autocomplete the rest of the directory name.
• Run g++ with the following command:
  • g++ -Wall -Wextra -o world hello.cpp
• No output means it worked!

Understanding the Command

g++ -Wall -Wextra -o world hello.cpp

g++ is the name of the compiler program and the rest of the lines are parameters.

Parameter	Parameter Description
-Wall	Enables additional warnings about questionable constructions that are easily avoid.
-Wextra	Enables even more helpful warnings.
-o world	Name the executable file we are creating “world”.
hello.cpp	The name of the input file (must be the last parameter).

Additional Useful Parameters

-fmax-errors=5

• This will tell the compiler to output at most 5 errors.
  • The number 5 can be changed to any number you want.
• Sometimes when we have one problem, it produces a ton of errors. Use this parameter to only show the first however many.
• Always look at the first error first.

-std=c++23

• This will tell the compiler to use the latest (2023) standard of C++.
• This may be necessary if you are using more recent features of the language.
• If your compiler doesn’t support the 2023 standard, you can try a previous standard:
  • -std=c++20 for the 2020 standard of C++
  • -std=c++17 for the 2017 standard of C++.

-pedantic or -Wpedantic

• GCC compilers always try to compile your program if this is at all possible. However, in some cases, the C++ standard specifies that certain extensions are forbidden.
• Use this option to receive warnings when your code can compile but is NOT valid C++.
• Helps track down errors and ensures a better assignment grade.

-Wmissing-declarations

• Notifies you if you accidentally define a function without a prototype (i.e. forward declaration).

Run the Hello Program

• To run your newly-compiled program, type the name of the program
  world
• In macOS or Linux, you may need to put a ./ before the program name.
  ./world