[MSX-C] Q&A official thread

I am trying to change the character set. So I want to create an array with the new values so I can ldirvm them straight in to VRAM. However, ascii C doesn't like arrays....

int nc[8] = { 0, 255, 0, 255, 0, 0, 0, 0 };

Compiler error: can't initialise, content of array is useless expressions. I've tried ' or " but that results in error missing quotes or useless expression. I've tried making it a char or a pointer, it didn't make a difference. How can I create an array and populate it with new values?

solved it for the time being with

char *nc = "\x28\x28\x28\x28\x2F\x20\x3F\x0\x0\x3F\x20\x2F\x28\x28\x28\x28\x0\xFF\x0\xFF\x0\x0\x0\x0\xFC\x4\xF4\x14\x14\x14\x14\x28\x28\x28\x28\x28\x28\x28\x28\x14\x14\x14\x14\xF4\x4\xFC\x0\x14\x14\x14\x14\x14\x14\x14\x14\x0\x0\x0\x0\xFF\x0\xFF\x0\x20\xE0\x20\xE0\x20\x0\x0\x0\x4\x7\x4\x7\x4\x0\x0\x0 ";

but this is ugly.

I am reading certain keys (CTRL, SHIFT, ESC) in a loop using ports (not snsmat). I want to start actions if people press CTRL-N, CTRL-D, CTRL-H. Pressing the ESC key inside this loop sets the escape flag. If no key is detected, wait one Jiffy and go back. The behaviour of the system is erratic to say the least, Sometimes it works, most of the times, it hangs. Is it possible that too often, reading the keyboard through the ports can hang the system? What is a good way to do this?

This is a nasty issue, happening in a larger project. This code below just shows what the compiler does with variables defined as unsigned through the project.

typedef struct {
  unsigned x;
  unsigned y;
} block;

main()
{
 block test;
 test.x=10;
 test.y=5;
printf("%u\n",test.x);     <- 10
printf("%u\n",test.y);    <- -5 !!! mark the minus sign
printf("%d\n",((test.y-1)*80)+test.x);     <- generates no output
printf("%u\n",((test.y-1)*80)+test.x);     <- 1125!!!
printf("%i\n",((y-1)*80)+10);      <- i, great ascii C doesn't support integer in printf....

}

anyone a clue what the compiler is doing here? Bitwise the result doesn't even look like the correct answer..

did no tests for negative values But assigning -64 to a char is not an issue for the compiler. Using 'unsigned char' returns a 'duplicate type definition error' because unsigned is a 2 byte value.

I don't know MSX-C, but maybe you have the equivalent of the .map files that SDCC generates? If so, you can see where each areas and labels are placed in memory space and understand why some elements are not where you want them.