Using the CP/M BDS C Compiler

I'll continue giving more details on the programs I demonstrated in the YouTube video The Briel Altair 8800 Kit, Part 5: Advanced Topics.

This time, the BDS C Compiler.

Go to Leo Zolman's BDS C web page and download the release file bdsc-all.zip.

BDS C comes with extensive documentation in the file bdsc-guide.pdf, but for the purposes of a simple demo, you can do the following. Unzip the file and copy these files to an SD card, and then transfer them to a CP/M drive:

BDSCIO.H C.CCC CC.COM CC2.COM
CLINK.COM DEFF.CRL DEFF2.CRL STDIO.H

The example program TAIL.C used in the demonstration was found here.

Here is an even shorter example C program that I  wrote. I entered it as the filename EX1.C:

/* BDS C example 1 */
#include

main(argc,argv)
char **argv;
{
    int i;

    printf("Example Program 1\n");
    for (i=1; i <=10; i++) {
        printf("%d\n", i);
    }
    return 0;
}

Here is a sample session showing EX1.C and TAIL.C being compiled, linked, and run (commands typed by the user are in bold).

B>dir

B: EX1      C   : NQUEENS  C   : BDSCIO   H   : C        CCC
B: CC       COM : CC2      COM : CLINK    COM : DEFF     CRL
B: DEFF2    CRL : STDIO    H   : TAIL     C

B>cc ex1

BD Software C Compiler v1.60  (part I)
  37K elbowroom
BD Software C Compiler v1.60 (part II)
  34K to spare

B>clink ex1

BD Software C Linker   v1.60

Last code address: 0E8D 
Externals start at 0E8E, occupy 0006 bytes, last byte at 0E93 
Top of memory: E805 
Stack space: D972 
Writing output...
  46K link space remaining

B>ex1

Example Program 1
1
2
3
4
5
6
7
8
9
10

B>cc tail

BD Software C Compiler v1.60  (part I)
  36K elbowroom
BD Software C Compiler v1.60 (part II)
  33K to spare

B>clink tail

BD Software C Linker   v1.60

Last code address: 1402 
Externals start at 1403, occupy 0006 bytes, last byte at 1408 
Top of memory: E805 
Stack space: D3FD 
Writing output...
  44K link space remaining

B>tail -10 tail.c

}
                                


int lastchar(c)
char c;
{
        return (!c) || (c == CPMEOF);
}

B>tail

Usage: tail [-#]

B>dir

B: TAIL     CRL : TAIL     COM : NQUEENS  CRL : NQUEENS  COM
B: EX1      C   : NQUEENS  C   : BDSCIO   H   : C        CCC
B: CC       COM : CC2      COM : CLINK    COM : DEFF     CRL
B: DEFF2    CRL : STDIO    H   : TAIL     C   : EX1      CRL
B: EX1      COM

Finally, here is the N Queens example program shown in the YouTube video. It will take a while to run to completion.   First the source code, followed by example output.

/* Solve the n queens problem */

#include

#define MAX_N 8

int  board[MAX_N*MAX_N];
int tries;
int  solutions;
int  n;
int  nsq;
int cache[MAX_N+1]; /* get some savings by caching last position */

/* display the board */
void print_board()
{
  int i;
  
  printf("+");
  for (i = 0; i < n ; i++)
    printf("---");
  printf("+\n");

  for (i = 0; i < nsq ; i++) {
    if ((i % n) == 0)
      printf("|");
    if (board[i])
      printf(" Q ");
    else
      printf(" . ");
    if (((i+1) % n) == 0)
      printf("|\n");
  }

  printf("+");
  for (i = 0; i < n ; i++)
    printf("---");
  printf("+\n");
}

/* find position of a piece */
int piece(n)
{
  int i;

  /* first try the cache */
  if (board[cache[n]] == n)
    return cache[n];
  
  for (i = 0 ; i < nsq ; i++)
    if (board[i] == n) {
      cache[n] = i; /* cache it for next time */
      return i;
    }
  return -1;
}

/* see if board is a solution */
void check_board()
{
  int i, p, r, c, j;

  /* loop over all pieces */
  for (i = 1 ; i <= n ; i++) {
    p = piece(i);

    /* not a solution if piece in same row */
    r = p / n;
    for (c = 0 ; c < n ; c++) {
      if (board[r*n+c] != 0 && board[r*n+c] != i)
return;
    }

    /* not a solution if piece in same column */
    c = p % n;
    for (r = 0 ; r < n ; r++) {
      if (board[r*n+c] != 0 && board[r*n+c] != i)
return;
    }
    
    /* not a solution if piece in same \ diagonal */
    for (j = -n ; j < n ; j++) {
      r = p / n + j;
      c = p % n + j;
      if ((r >= 0) && (r < n) && (c >= 0) && (c < n) &&
 (board[r*n+c] != 0) && (board[r*n+c] != i))
return;
    }
    /* not a solution if piece in same / diagonal */
    for (j = -n ; j < n ; j++) {
      r = p / n + j;
      c = p % n - j;
      if ((r >= 0) && (r < n) && (c >= 0) && (c < n) &&
 (board[r*n+c] != 0) && (board[r*n+c] != i))
return;
    }
  }
  solutions++;
  print_board();
}

/* move piece p to next position */
int next_pos(p)
{
  int i, t;

  if (p < 1)
    return 0;

  i = piece(p);

  if (i < nsq-n+p-1) {
    board[i] = 0;
    board[i+1] = p;
    return 1;
  } else {
    t = next_pos(p-1);
    board[i] = 0;
    board[piece(p-1)+1] = p;
    return t;
  }
}

/* generate the next possible solution */
int next_board()
{
  return next_pos(n);
}


int main()
{
  int i;

  solutions = 0;
  n = 5;
  nsq = n*n;           /* save n^2 to avoid calculating it again */

  printf("\n\n\n\nSOLVING N QUEENS PROBLEM FOR N = %d\n", n);

  /* clear the board */
  for (i = 0 ; i < nsq ; i++)
    board[i] = 0;

  /* initially place the queens */
  for (i = 0 ; i < n ; i++)
    board[i] = i+1;

  do {
    tries++;
    check_board();
  } while (next_board());
  
  printf("FOUND %d SOLUTIONS AFTER %ld TRIES.\n", solutions, tries);
        
  return 0;
}

B>nqueens

SOLVING N QUEENS PROBLEM FOR N = 5
+---------------+
| Q  .  .  .  . |
| .  .  Q  .  . |
| .  .  .  .  Q |
| .  Q  .  .  . |
| .  .  .  Q  . |
+---------------+
+---------------+
| Q  .  .  .  . |
| .  .  .  Q  . |
| .  Q  .  .  . |
| .  .  .  .  Q |
| .  .  Q  .  . |
+---------------+
+---------------+
| .  Q  .  .  . |
| .  .  .  Q  . |
| Q  .  .  .  . |
| .  .  Q  .  . |
| .  .  .  .  Q |
+---------------+
+---------------+
| .  Q  .  .  . |
| .  .  .  .  Q |
| .  .  Q  .  . |
| Q  .  .  .  . |
| .  .  .  Q  . |
+---------------+
+---------------+
| .  .  Q  .  . |
| Q  .  .  .  . |
| .  .  .  Q  . |
| .  Q  .  .  . |
| .  .  .  .  Q |
+---------------+
+---------------+
| .  .  Q  .  . |
| .  .  .  .  Q |
| .  Q  .  .  . |
| .  .  .  Q  . |
| Q  .  .  .  . |
+---------------+
+---------------+
| .  .  .  Q  . |
| Q  .  .  .  . |
| .  .  Q  .  . |
| .  .  .  .  Q |
| .  Q  .  .  . |
+---------------+
+---------------+
| .  .  .  Q  . |
| .  Q  .  .  . |
| .  .  .  .  Q |
| .  .  Q  .  . |
| Q  .  .  .  . |
+---------------+
+---------------+
| .  .  .  .  Q |
| .  Q  .  .  . |
| .  .  .  Q  . |
| Q  .  .  .  . |
| .  .  Q  .  . |
+---------------+
+---------------+
| .  .  .  .  Q |
| .  .  Q  .  . |
| Q  .  .  .  . |
| .  .  .  Q  . |
| .  Q  .  .  . |
+---------------+
FOUND 10 SOLUTIONS AFTER -12406 TRIES.

B>