Commit 887c0528 authored by Erik Strand's avatar Erik Strand
Browse files

Write main README and basic hello worlds

parent 397fc836
build
*.swo
*.swp
.DS_Store
hello_world_c
hello_world_cpp
# Change your compiler here if you're not using gcc. CC is for C, and CXX is for C++.
CC = gcc
CXX = g++
# These are options that we pass to the compiler. They say to emit all warnings ("warn all"), and
# optimize the program aggresively to make it fast ("optimization level 3").
CFLAGS = -Wall -O3
# This line is here so that by default, Make will build both programs. It's not strictly necessary.
# With or without this line, you can run "make hello_world_c" or "make hello_world_cpp". With this
# line, if you just run "make" you'll get both. (Make executes the first rule in the Makefile when
# you don't give it a target specifically, so we put this rule first.) We tell Make that this rule
# is "phony" so that it understands it's just a combination of other rules and doesn't produce any
# of its own files.
.PHONY: all
all: hello_world_c hello_world_cpp
# These are essentially recipes for programs. The first line tells Make that we are going to build
# a program "hello_world_c" from the source file "hello_world.c". The second lines Make how to
# do it; Make basically copies and pastes this line into the terminal. Note that to use the compiler
# and options we defined earlier (CC, CXX, and CFLAGS), we have to enclose them in parentheses and
# add a dollar sign.
hello_world_c: hello_world.c
$(CC) $(CFLAGS) -o hello_world_c hello_world.c
# Here's the same thing except for the C++ version.
hello_world_cpp: hello_world.cpp
$(CXX) $(CFLAGS) -o hello_world_cpp hello_world.cpp
# This rule deletes all the binaries. It's declared "phony" which means it doesn't actually make
# anything. Otherwise Make would get confused about when it should run this rule.
.PHONY: clean
clean:
rm hello_world_c hello_world_cpp
# Hello World
From this directory (i.e. first run `cd /wherever/you/put/this/repo/01_hello_world`), run `make`. If
your toolchain is installed correctly, this will build two programs: `hello_world_c` and
`hello_world_cpp`. You can run them like this: `./hello_world_c` and `./hello_world_cpp`.
```
demo@linux:01_hello_world$ make
gcc -Wall -O3 -o hello_world_c hello_world.c
g++ -Wall -O3 -o hello_world_cpp hello_world.cpp
demo@linux:01_hello_world$ ./hello_world_c
hello, world, I'm C
demo@linux:01_hello_world$ ./hello_world_cpp
hello, world, I'm C++
```
Note: Putting `./` in front of the executable files tells the shell unambiguously that you want to
run the programs located in this directory. The shell will say something like `command not found` if
you leave it out. This might seem annoying, but it's really important from a security perspective.
Otherwise if you made a program called `cd` or `make` or something, you could accidentally run it
and it might do something bad.
#include <stdio.h>
// Every C program has a function called main. This is where your program starts.
int main(void) {
printf("hello, world, I'm C\n");
}
#include <iostream>
// C++ uses a main routine just like C. We could use printf here, too, but it's more idiomatic to
// use std::cout.
int main() {
std::cout << "hello, world, I'm C++\n";
}
# c_cpp_and_make # C, C++, and Makefiles
Hello world programs for C and C++, built with Makefiles. Microcontrollers are great and all, but if you're new to programming it can help to learn a bit
\ No newline at end of file about the software tools on their own before diving into the hardware as well. This repo has some
example programs in C and C++, along with Makefiles that help you build them.
## The Basics
C is a programming language. It was created in the early 70s at Bell Labs by Dennis Ritchie and Ken
Thompson. This makes it quite old, as far as programming languages go, but it certainly wasn't the
first (Fortran, Lisp, COBOL, and BASIC are all older, to name a few). And it's still widely used
today -- number one, in fact, in some popularity [rankings](https://www.tiobe.com/tiobe-index/).
C++ is an extended version of C, created by Bjarne Stroustrup in the 80s. The syntax is basically
the same, so usually any C program you write will also be a valid C++ program. The original
difference is that C++ is [object
oriented](https://en.wikipedia.org/wiki/Object-oriented_programming) (basically, allows you to
associate data and methods with "classes"), but since then it's had all sorts of other stuff bolted
on too (like [templates](https://en.wikipedia.org/wiki/Template_(C%2B%2B)),
[lambdas](https://stackoverflow.com/questions/7627098/what-is-a-lambda-expression-in-c11), etc.). C
and C++ are commonly used together.
Unlike Python or JavaScript, C and C++ are compiled languages. This means that before you run your
program, you always convert it into a binary format that your computer can execute directly. This is
called building your program, and it is done by a compiler. To run code on your own computer, you'll
almost certainly end up using [gcc](https://gcc.gnu.org/), [clang](https://clang.llvm.org/), or
[MSVC](https://visualstudio.microsoft.com/vs/features/cplusplus/). The first two are usually run
from the command line, while the third is integrated into Visual Studio. We'll be using the UNIX
style command line exclusively, so even if you run Windows, it's recommended that you install a
command line toolchain.
## Required Software
Overall, we'll need a compiler, and [Make](https://www.gnu.org/software/make/).
On Linux, if these tools aren't installed already, you can use your package manager. Most distros
have one package that has all the basic tools bundled together. On Ubuntu, for example, you can run
`sudo apt install build-essential`.
On Mac, if you've installed XCode, you already have clang. (You may need to tell XCode to install
the command line tools specifically for it to show up on your path.) You can also use homebrew to
install gcc. One gotcha is that Apple decided to alias clang as gcc in the stock install. So if you
run gcc, you'll actually get clang. This is bad because not all the options are the same, so
sometimes it just won't work to switch between the two. So if you do install gcc with homebrew,
you'll want to run gcc-8 or gcc-9 (or whatever specific version you got).
On Windows... honestly I'm not sure. I haven't set up a development environment there in years.
## Examples
- [hello world](./01_hello_world)
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