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content/guides/old3ds_helloworld.md

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+---
+title: 3DS Programming - Hello World
+description: A guide to creating a simple Hello, World program for the 3DS. (Old)
+date: 2025-01-01
+tags: ['3ds', 'programming', 'c', 'devkitpro', 'old']
+next: old3ds_romfs.md
+---
+
+# Hello, World!
+
+::alert{type="warning"}
+This guide of mine is old - Like 3 years old at the time of posting. I prefer to keep it up, but I don't think it very highly - It should still work though.
+I might make a new one in the future.
+I'm doing some alterations at least to make it more readable.
+It doesn't teach why things are done very well is my primary issue with it.
+::
+
+'Hello, World!' is a very simple program used for checking a program's build system, and showing its basic syntax.
+We should do both before going forward. You should have your project set up for this.
+
+And if you are using VSCode, I would recommend you get the include paths set up.
+
+## Begin coding
+
+Start by including 'stdio.h' (or 'cstdio'!) and '3ds.h'.
+A quick explanation of '3ds.h'
+
+'3ds.h' is the file containing references to all the VITAL things we can use to program on the system.
+
+It does not include many features, such as (And certainly not limited to) rendering capabilities, aside from running the console)
+
+## Main loop
+
+Start by setting up a main function as usual for C/C++.
+
+To initialize the graphics, we need to run gfxInitDefault().
+
+To initialize the console, we need to run consoleInit([SCREEN HERE], NULL).
+
+Replace '[SCREEN HERE]' with either GFX_TOP or GFX_BOTTOM, depending on what screen you want.
+
+At this point, the code should look something like this:
+
+<!-- Note: I originally used images for these, but... Why did I do that? -->
+
+```c
+#include <stdio.h>
+#include <3ds.h>
+
+int main() {
+    // Initialize the console
+    gfxInitDefault();
+    consoleInit(GFX_BOTTOM, NULL);
+
+    return 0;
+}
+```
+
+As the console is now ready, you can now print to the screen. You can use puts(), printf(), std::cout, etc.
+
+If we try and run it now, it should immediately close itself, as there is no main loop.
+
+To create a main loop, we create a while loop with aptMainLoop() as its argument:
+
+```c
+// Initialize the console
+// ...
+
+/// Main loop
+while(aptMainLoop()) {
+    // Code here
+}
+```
+
+This will loop infinitely until the user closes the program.
+
+## Input
+
+Okay, so we now have a main loop... How do we exit back to the Homebrew Launcher?
+
+Simple. We can scan for input, and break if it detects a button, in this case START, being pressed.
+
+We can scan for input with hidScanInput(), and get which keys are down with hidKeysDown() like so:
+
+```c
+// Main loop
+while(aptMainLoop()) {
+    // Scan for input
+    hidScanInput();
+    u32 kDown = hidKeysDown();
+}
+```
+
+Every button is mapped to a different bit on the unsigned 32-bit integer.
+
+We can get specific keys via an AND operation between the integer and the desired key:
+
+```c
+// Main loop
+while(aptMainLoop()) {
+    // Scan for input
+    hidScanInput();
+    u32 kDown = hidKeysDown();
+
+    // Break if START is pressed
+    if(kDown & KEY_START) break;
+}
+```
+
+## Wrapping up
+
+We can add V-Sync with gspWaitForVBlank(), which may help if you want that and don't want to draw anything aside from the console. You can disregard this if you want:
+
+```c
+// Main loop
+while(aptMainLoop()) {
+    // Scan for input
+    // ...
+    // Break if START is pressed
+    // ...
+
+    // Wait for V-Blank
+    gspWaitForVBlank();
+}
+
+```
+
+And we are done. You can run the program, and get the words 'Hello, World!' printed on the screen:
+
+![Failed to load image](/files/old3ds/helloworld/dkp_progress0.png)