Lesson 02
Setting up the Development Environment
The setup, creation, and execution or a "Hello World"
So, after reading Lesson 01, you
have a working development environment in which to create your programs. Now what? Well, this is the part
you've all been waiting for, your very first program for the PSP. This tutorial will explain the basics of
the C programming language and build the foundation upon which you will build your kingd-- err... programs.
If, at any time in this tutorial, you need help please head over to our forums and post a question. We are always happy to help a fellow programmer.
We're going to create a folder hierarchy to organize our projects. Open up a CYGWIN bash shell, and
type "mkdir projects" and then hit enter. This command ("mkdir") stands for "make directory" and it
will create a directory, or folder, in your current operating directory. So now we have a new folder
for all of our projects, navigate into it by typing "cd projects" and hitting enter. Now we are going
to create another directory for this specific project. Type "mkdir helloworld" and hit enter. Now
switch into the new directory with "cd helloworld."
The next step is to open up a text editor. It doesn't really matter what you open, it can be Notepad,
Wordpad, whatever you want. I prefer using an editor that is dedicated to editting C/C++ source code
because of the syntax highlighting options that are built in (I use
Dev-C++),
but honestly, it doesn't matter (so long as you know how to use it).
Now, create a new file and call it "main.c" in our "helloworld" directory. This is going to contain the source code for our program. For those of you who don't know what source code is (and I know there will be a few), the source code is what we write to create a program. It is written in a way that humans can understand. In most languages, the source needs to be converted to a format the computer (or in our case, the PSP) can understand. These are called compiled languages, and C and C++ fall into this category (the conversion is done by the compiler that we set up in Lesson 01). There are a few other programming languages that use what is called an interpreter to interpret the source code and send out machine code on the fly. These are called scripting languages (an example of a scripting language is PHP).
Alright, so we have a new file that is going to hold our source code. Now we need to start writing it. The first part of the program should contain comments to tell anyone reading our code what the aim of the program is, when it was written, and who the author is. Comments are lines of source code that are omitted from the compiled binary (or skipped by the interpretter in scripting languages). Comments are a very important part of your code, because when you (or someone else) come back to edit your source code later, you will not remember all of the intricacies of the program. So, you can leave yourself notes in the form of comments. Comments are signalled with the "//" and "/*" characters. Any time you see a "//" it means that the rest of the line will be a comment. A "/*" means that the compiler (or interpretter) will ignore your code until it reaches a "*/" signal. Comments signalled by the "/*" operator can span many lines, but comments signalled with "//" only comment out the rest of that line.
So, to start off our program, we are going to leave a comment at the top about what it does, when it was created, and who it was written by.
If, at any time in this tutorial, you need help please head over to our forums and post a question. We are always happy to help a fellow programmer.
Now, create a new file and call it "main.c" in our "helloworld" directory. This is going to contain the source code for our program. For those of you who don't know what source code is (and I know there will be a few), the source code is what we write to create a program. It is written in a way that humans can understand. In most languages, the source needs to be converted to a format the computer (or in our case, the PSP) can understand. These are called compiled languages, and C and C++ fall into this category (the conversion is done by the compiler that we set up in Lesson 01). There are a few other programming languages that use what is called an interpreter to interpret the source code and send out machine code on the fly. These are called scripting languages (an example of a scripting language is PHP).
Alright, so we have a new file that is going to hold our source code. Now we need to start writing it. The first part of the program should contain comments to tell anyone reading our code what the aim of the program is, when it was written, and who the author is. Comments are lines of source code that are omitted from the compiled binary (or skipped by the interpretter in scripting languages). Comments are a very important part of your code, because when you (or someone else) come back to edit your source code later, you will not remember all of the intricacies of the program. So, you can leave yourself notes in the form of comments. Comments are signalled with the "//" and "/*" characters. Any time you see a "//" it means that the rest of the line will be a comment. A "/*" means that the compiler (or interpretter) will ignore your code until it reaches a "*/" signal. Comments signalled by the "/*" operator can span many lines, but comments signalled with "//" only comment out the rest of that line.
So, to start off our program, we are going to leave a comment at the top about what it does, when it was created, and who it was written by.
// Hello World - My First App for the PSP
/*
This program was created by (Your Name Here) on (Date Here)
It is a simple "Hello World" Application.
*/
The next portion of the program is where we tell the compiler which header files and which include files we are going to
use in our program. Basically what the "#include" directive does is copy the code from the file you pass to it into the
top of your program. This allows you to keep your program simple, while still using the advanced code that is already
written for you. The include directive can include either header files that came with the compiler (or that you add to
the compiler), or header files specific to the specific project that you are working on. The way that you discern which
of these you are including is by whether you use "<>" to enclose the file or if you use quotes to do it. The less
than and greater than signs include a file from the compiler's "include" directory, and the quotes include a file from
the same directory as the file including them. We will be including two files in our program. The first is "pspkernel.h."
This file will be included in every single program that you write for the PSP. It contains all of the code specific to
your PSP. Your program will not work on the PSP if you do not include this file. The second file we are going to include
is "pspdebug.h." This file contains several useful functions for debugging your programs, but specifically it includes
the function that we are going to use to write text to the screen. So, add this code to your program:
/*
This program was created by (Your Name Here) on (Date Here)
It is a simple "Hello World" Application.
*/
#include <pspkernel.h>
#include <pspdebug.h>
Next we tell the PSP a little bit about the program. This isn't really that important, your program will compile without
it, but it is always a good idea to keep it in (if only for forwards compatibility). The first attribute is the name of
the program, but it's not really the name of the program that will appear (we'll change that later). The other
values are other attributes (just leave it alone), major version, and minor version. We'll just leave all of these except
for the name as the defaults. So, add the following line to your program:
#include <pspdebug.h>
PSP_MODULE_INFO("Hello World", 0, 1, 1);
Now we are going to set up the function that we will use to write to the screen. This step is optional, but it makes writing
text based programs much easier. The basis behind this line is to change the function that is built into the PSP, called
"pspDebugScreenPrintf" into something that's much easier to type. This function is used to write to the screen (which you will
see later). What we are basically going to do here is rename "pspDebugScreenPrintf" to "printf." So every time we use "printf"
from now on, the compiler will just treat it as if we have typed "pspDebugScreenPrintf." Here's how we'll do it; we'll define
"printf" as "pspDebugScreenPrintf" like this:
#define printf pspDebugScreenPrintf
Take a deep breath. Ok, now breath out. Good. Now continue to the second part of the tutorial.