C programming on a legacy console system.

This is a discussion on C programming on a legacy console system. within the C Programming forums, part of the General Programming Boards category; I own an Atari Jaguar legacy console system. I'm trying to wrap my head around how its C setup displays ...

  1. #1
    Registered User
    Join Date
    Sep 2006
    Location
    Beaverton, Oregon, United States
    Posts
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    C programming on a legacy console system.

    I own an Atari Jaguar legacy console system. I'm trying to wrap my head around how its C setup displays graphics at a basic level. I have no experience with graphics so am trying to start at the beginning with this system, the simplest HELLO C program it has. I figured that would be a good place to start. I'm going to post the full source code for it in this thread and I'd like to thank everyone for their patience with me as I post questions while trying to decipher the source code.

    Code:
    #include"font.h"
    
    extern void *vidmem;
    unsigned char *jagscreen;
    
    void DrawCharLine (int charloc, int screenloc)
    {
      static unsigned char shift[] = { 7, 6, 5, 4, 3, 2, 1, 0 };
      int xcnt;
    
      for (xcnt = 0; xcnt < F_WIDTH; xcnt++) 
      {
        if (((textfont[charloc] >> shift[xcnt]) & 0x1)) 
          jagscreen[screenloc++] = 1;
        else
          jagscreen[screenloc++] = 0;
      }
    }
    
    void DrawChar (int x, int y, char ch)
    {
      int ycnt, charloc, screenloc;
    
      charloc = ch * F_CHARSIZE;
    
      screenloc = (y * T_XREZ) + x ;
    
      for (ycnt = 0; ycnt < F_HEIGHT; ycnt++) 
      {
        DrawCharLine (charloc, screenloc);
        screenloc += T_XREZ;
        charloc++;
      }
    }
    
    void DrawString (int x, int y, char *str)
    {
      int cnt;
    
      for (cnt = 0; str[cnt] != 0; cnt++) 
      {
        DrawChar (x, y, str[cnt]);
        x += F_WIDTH;
      }
    }
    
    
    void __main(void) 
    {
      int w,x=5,y=130;
    
      jagscreen = (unsigned char *)&vidmem;
    
      *(unsigned short int *) 0xf00400 = 0x0000; /* Color reg 0 = black */
      *(unsigned short int *) 0xf00402 = 0xffff; /* Color reg 1 = white */
    
      for(w=0; w<64000; w++) jagscreen[w]=0;
      
    
    	DrawString(x,y,"Hello Jag Users");
    
    
    
      for(;;);  /* Infinite Loop.  Alpine users can delete this.  */
    }
    FONT.H

    Code:
    #define F_WIDTH          0x08
    #define F_HEIGHT         0x08
    #define F_CHARSIZE       0x08
    
    #define T_XREZ           320
    #define T_YREZ           200
    
    
    
    unsigned char textfont[] =
      { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7E, 0x81, 0xA5, 0x81,
        0xBD, 0x99, 0x81, 0x7E, 0x7E, 0xFF, 0xDB, 0xFF, 0xC3, 0xE7, 0xFF, 0x7E,
        0x6C, 0xFE, 0xFE, 0xFE, 0x7C, 0x38, 0x10, 0x00, 0x10, 0x38, 0x7C, 0xFE,
        0x7C, 0x38, 0x10, 0x00, 0x38, 0x7C, 0x38, 0xFE, 0xFE, 0x7C, 0x38, 0x7C,
        0x10, 0x10, 0x38, 0x7C, 0xFE, 0x7C, 0x38, 0x7C, 0x00, 0x00, 0x18, 0x3C,
        0x3C, 0x18, 0x00, 0x00, 0xFF, 0xFF, 0xE7, 0xC3, 0xC3, 0xE7, 0xFF, 0xFF,
        0x00, 0x3C, 0x66, 0x42, 0x42, 0x66, 0x3C, 0x00, 0xFF, 0xC3, 0x99, 0xBD,
        0xBD, 0x99, 0xC3, 0xFF, 0x0F, 0x07, 0x0F, 0x7D, 0xCC, 0xCC, 0xCC, 0x78,
        0x3C, 0x66, 0x66, 0x66, 0x3C, 0x18, 0x7E, 0x18, 0x3F, 0x33, 0x3F, 0x30,
        0x30, 0x70, 0xF0, 0xE0, 0x7F, 0x63, 0x7F, 0x63, 0x63, 0x67, 0xE6, 0xC0,
        0x99, 0x5A, 0x3C, 0xE7, 0xE7, 0x3C, 0x5A, 0x99, 0x80, 0xE0, 0xF8, 0xFE,
        0xF8, 0xE0, 0x80, 0x00, 0x02, 0x0E, 0x3E, 0xFE, 0x3E, 0x0E, 0x02, 0x00,
        0x18, 0x3C, 0x7E, 0x18, 0x18, 0x7E, 0x3C, 0x18, 0x66, 0x66, 0x66, 0x66,
        0x66, 0x00, 0x66, 0x00, 0x7F, 0xDB, 0xDB, 0x7B, 0x1B, 0x1B, 0x1B, 0x00,
        0x3E, 0x63, 0x38, 0x6C, 0x6C, 0x38, 0xCC, 0x78, 0x00, 0x00, 0x00, 0x00,
        0x7E, 0x7E, 0x7E, 0x00, 0x18, 0x3C, 0x7E, 0x18, 0x7E, 0x3C, 0x18, 0xFF,
        0x18, 0x3C, 0x7E, 0x18, 0x18, 0x18, 0x18, 0x00, 0x18, 0x18, 0x18, 0x18,
        0x7E, 0x3C, 0x18, 0x00, 0x00, 0x18, 0x0C, 0xFE, 0x0C, 0x18, 0x00, 0x00,
        0x00, 0x30, 0x60, 0xFE, 0x60, 0x30, 0x00, 0x00, 0x00, 0x00, 0xC0, 0xC0,
        0xC0, 0xFE, 0x00, 0x00, 0x00, 0x24, 0x66, 0xFF, 0x66, 0x24, 0x00, 0x00,
        0x00, 0x18, 0x3C, 0x7E, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0x7E,
        0x3C, 0x18, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x30, 0x78, 0x78, 0x78, 0x30, 0x00, 0x30, 0x00, 0x6C, 0x6C, 0x6C, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x6C, 0x6C, 0xFE, 0x6C, 0xFE, 0x6C, 0x6C, 0x00,
        0x30, 0x7C, 0xC0, 0x78, 0x0C, 0xF8, 0x30, 0x00, 0x00, 0xC6, 0xCC, 0x18,
        0x30, 0x66, 0xC6, 0x00, 0x38, 0x6C, 0x38, 0x76, 0xDC, 0xCC, 0x76, 0x00,
        0x60, 0x60, 0xC0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x30, 0x60, 0x60,
        0x60, 0x30, 0x18, 0x00, 0x60, 0x30, 0x18, 0x18, 0x18, 0x30, 0x60, 0x00,
        0x00, 0x66, 0x3C, 0xFF, 0x3C, 0x66, 0x00, 0x00, 0x00, 0x30, 0x30, 0xFC,
        0x30, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x30, 0x30, 0x60,
        0x00, 0x00, 0x00, 0xFC, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x30, 0x30, 0x00, 0x06, 0x0C, 0x18, 0x30, 0x60, 0xC0, 0x80, 0x00,
        0x7C, 0xC6, 0xCE, 0xDE, 0xF6, 0xE6, 0x7C, 0x00, 0x30, 0x70, 0x30, 0x30,
        0x30, 0x30, 0xFC, 0x00, 0x78, 0xCC, 0x0C, 0x38, 0x60, 0xCC, 0xFC, 0x00,
        0x78, 0xCC, 0x0C, 0x38, 0x0C, 0xCC, 0x78, 0x00, 0x1C, 0x3C, 0x6C, 0xCC,
        0xFE, 0x0C, 0x1E, 0x00, 0xFC, 0xC0, 0xF8, 0x0C, 0x0C, 0xCC, 0x78, 0x00,
        0x38, 0x60, 0xC0, 0xF8, 0xCC, 0xCC, 0x78, 0x00, 0xFC, 0xCC, 0x0C, 0x18,
        0x30, 0x30, 0x30, 0x00, 0x78, 0xCC, 0xCC, 0x78, 0xCC, 0xCC, 0x78, 0x00,
        0x78, 0xCC, 0xCC, 0x7C, 0x0C, 0x18, 0x70, 0x00, 0x00, 0x30, 0x30, 0x00,
        0x00, 0x30, 0x30, 0x00, 0x00, 0x30, 0x30, 0x00, 0x00, 0x30, 0x30, 0x60,
        0x18, 0x30, 0x60, 0xC0, 0x60, 0x30, 0x18, 0x00, 0x00, 0x00, 0xFC, 0x00,
        0x00, 0xFC, 0x00, 0x00, 0x60, 0x30, 0x18, 0x0C, 0x18, 0x30, 0x60, 0x00,
        0x78, 0xCC, 0x0C, 0x18, 0x30, 0x00, 0x30, 0x00, 0x7C, 0xC6, 0xDE, 0xDE,
        0xDE, 0xC0, 0x78, 0x00, 0x30, 0x78, 0xCC, 0xCC, 0xFC, 0xCC, 0xCC, 0x00,
        0xFC, 0x66, 0x66, 0x7C, 0x66, 0x66, 0xFC, 0x00, 0x3C, 0x66, 0xC0, 0xC0,
        0xC0, 0x66, 0x3C, 0x00, 0xF8, 0x6C, 0x66, 0x66, 0x66, 0x6C, 0xF8, 0x00,
        0x7E, 0x60, 0x60, 0x78, 0x60, 0x60, 0x7E, 0x00, 0x7E, 0x60, 0x60, 0x78,
        0x60, 0x60, 0x60, 0x00, 0x3C, 0x66, 0xC0, 0xC0, 0xCE, 0x66, 0x3E, 0x00,
        0xCC, 0xCC, 0xCC, 0xFC, 0xCC, 0xCC, 0xCC, 0x00, 0x78, 0x30, 0x30, 0x30,
        0x30, 0x30, 0x78, 0x00, 0x1E, 0x0C, 0x0C, 0x0C, 0xCC, 0xCC, 0x78, 0x00,
        0xE6, 0x66, 0x6C, 0x78, 0x6C, 0x66, 0xE6, 0x00, 0x60, 0x60, 0x60, 0x60,
        0x60, 0x60, 0x7E, 0x00, 0xC6, 0xEE, 0xFE, 0xFE, 0xD6, 0xC6, 0xC6, 0x00,
        0xC6, 0xE6, 0xF6, 0xDE, 0xCE, 0xC6, 0xC6, 0x00, 0x38, 0x6C, 0xC6, 0xC6,
        0xC6, 0x6C, 0x38, 0x00, 0xFC, 0x66, 0x66, 0x7C, 0x60, 0x60, 0xF0, 0x00,
        0x78, 0xCC, 0xCC, 0xCC, 0xDC, 0x78, 0x1C, 0x00, 0xFC, 0x66, 0x66, 0x7C,
        0x6C, 0x66, 0xE6, 0x00, 0x78, 0xCC, 0xE0, 0x70, 0x1C, 0xCC, 0x78, 0x00,
        0xFC, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x00, 0xCC, 0xCC, 0xCC, 0xCC,
        0xCC, 0xCC, 0xFC, 0x00, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0x78, 0x30, 0x00,
        0xC6, 0xC6, 0xC6, 0xD6, 0xFE, 0xEE, 0xC6, 0x00, 0xC6, 0xC6, 0x6C, 0x38,
        0x38, 0x6C, 0xC6, 0x00, 0xCC, 0xCC, 0xCC, 0x78, 0x30, 0x30, 0x78, 0x00,
        0xFE, 0x06, 0x0C, 0x18, 0x30, 0x60, 0xFE, 0x00, 0x78, 0x60, 0x60, 0x60,
        0x60, 0x60, 0x78, 0x00, 0xC0, 0x60, 0x30, 0x18, 0x0C, 0x06, 0x02, 0x00,
        0x78, 0x18, 0x18, 0x18, 0x18, 0x18, 0x78, 0x00, 0x10, 0x38, 0x6C, 0xC6,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF,
        0x30, 0x30, 0x18, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x78, 0x0C,
        0x7C, 0xCC, 0x76, 0x00, 0xE0, 0x60, 0x60, 0x7C, 0x66, 0x66, 0xDC, 0x00,
        0x00, 0x00, 0x78, 0xCC, 0xC0, 0xCC, 0x78, 0x00, 0x1C, 0x0C, 0x0C, 0x7C,
        0xCC, 0xCC, 0x76, 0x00, 0x00, 0x00, 0x78, 0xCC, 0xFC, 0xC0, 0x78, 0x00,
        0x38, 0x6C, 0x60, 0xF0, 0x60, 0x60, 0xF0, 0x00, 0x00, 0x00, 0x76, 0xCC,
        0xCC, 0x7C, 0x0C, 0xF8, 0xE0, 0x60, 0x6C, 0x76, 0x66, 0x66, 0xE6, 0x00,
        0x30, 0x00, 0x70, 0x30, 0x30, 0x30, 0x78, 0x00, 0x0C, 0x00, 0x0C, 0x0C,
        0x0C, 0xCC, 0xCC, 0x78, 0xE0, 0x60, 0x66, 0x6C, 0x78, 0x6C, 0xE6, 0x00,
        0x70, 0x30, 0x30, 0x30, 0x30, 0x30, 0x78, 0x00, 0x00, 0x00, 0xCC, 0xFE,
        0xFE, 0xD6, 0xC6, 0x00, 0x00, 0x00, 0xF8, 0xCC, 0xCC, 0xCC, 0xCC, 0x00,
        0x00, 0x00, 0x78, 0xCC, 0xCC, 0xCC, 0x78, 0x00, 0x00, 0x00, 0xDC, 0x66,
        0x66, 0x7C, 0x60, 0xF0, 0x00, 0x00, 0x76, 0xCC, 0xCC, 0x7C, 0x0C, 0x1E,
        0x00, 0x00, 0xDC, 0x76, 0x66, 0x60, 0xF0, 0x00, 0x00, 0x00, 0x7C, 0xC0,
        0x78, 0x0C, 0xF8, 0x00, 0x10, 0x30, 0x7C, 0x30, 0x30, 0x34, 0x18, 0x00,
        0x00, 0x00, 0xCC, 0xCC, 0xCC, 0xCC, 0x76, 0x00, 0x00, 0x00, 0xCC, 0xCC,
        0xCC, 0x78, 0x30, 0x00, 0x00, 0x00, 0xC6, 0xD6, 0xFE, 0xFE, 0x6C, 0x00,
        0x00, 0x00, 0xC6, 0x6C, 0x38, 0x6C, 0xC6, 0x00, 0x00, 0x00, 0xCC, 0xCC,
        0xCC, 0x7C, 0x0C, 0xF8, 0x00, 0x00, 0xFC, 0x98, 0x30, 0x64, 0xFC, 0x00,
        0x1C, 0x30, 0x30, 0xE0, 0x30, 0x30, 0x1C, 0x00, 0x18, 0x18, 0x18, 0x00,
        0x18, 0x18, 0x18, 0x00, 0xE0, 0x30, 0x30, 0x1C, 0x30, 0x30, 0xE0, 0x00,
        0x76, 0xDC, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x38, 0x6C,
        0xC6, 0xC6, 0xFE, 0x00, 0xE9
    };

  2. #2
    Registered User
    Join Date
    Sep 2006
    Location
    Beaverton, Oregon, United States
    Posts
    156
    Code:
    void DrawChar (int x, int y, char ch)
    {
      int ycnt, charloc, screenloc;
    
      charloc = ch * F_CHARSIZE;
    
      screenloc = (y * T_XREZ) + x;
    
      for (ycnt = 0; ycnt < F_HEIGHT; ycnt++) 
      {
    	DrawCharLine (charloc, screenloc);
    	screenloc += T_XREZ;
    	charloc++;
      }
    }
    My first specific question from the above code. In the first pass it passes the character 'H' from 'Hello Jag users! '

    So the line :

    Code:
    charloc = ch * F_CHARSIZE;
    translates to 'charloc = 'H' * 0x08;

    Is this multiplying the character H by 0x08 hexadecimal? I'm not following this line all that clearly.

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