This simple program outputs "Hello world from PSX"

#include <psx.h>
#include <stdio.h>

unsigned int prim_list[0x4000];
volatile int display_is_old = 1;
volatile int time_counter = 0;
int  dbuf=0;

void prog_vblank_handler() {
    display_is_old = 1;
    time_counter++;
}

int main() {
    PSX_Init();
    GsInit();
    GsSetList(prim_list);
    GsClearMem();
    GsSetVideoMode(320, 240, EXAMPLES_VMODE);
    GsLoadFont(768, 0, 768, 256);
    SetVBlankHandler(prog_vblank_handler);

    while(1) {
        if(display_is_old)  {
            dbuf=!dbuf;
            GsSetDispEnvSimple(0, dbuf ? 0 : 256);
            GsSetDrawEnvSimple(0, dbuf ? 256 : 0, 320, 240);
            GsSortCls(0,0,0);

            GsPrintFont(70, 120, "Hello world from PSX");

            GsDrawList();
            while(GsIsDrawing());
            display_is_old=0;
        }
    }

    return 0;
}