Allowing the Aztec C-compiler to work - SysCallWriteRand was broken

[skx]

This pull request, once complete, will close #38 by resolving the problem that keeps the AS.com assembler from assembling a working output file (.O).

The problem seems to be related to file-based I/O, but I've not yet worked out out.

So far this pull request:

• Adds more debug-output
• Switches to using fcb.SIZE rather than 36 to avoid mistakes.
• Updates to use the real slice offsets for data-copies.
• Corrects a bug where the DMA area was hardcoded to be 0x0080 for FindFirst
  • This didn't help, but was obviously wrong.

I've added two new files beneath samples/:

• write.asm / write.com
  • Write 255 sequential records to a file, containing ascending blocks.
    • i.e one block of 0x00 bytes, then one block of 0x01 bytes.
• read.asm / read.com
  • Perform 255 sequential reads to a file, verify the contents are correct.
  • i.e. block 0x00 should have contents onlyu of 0x00, block 0x01 should contain 0x01, block 0xcd should contain only 0xcd, etc.

No errors/surprises in the sequential reads/writes. This strongly makes me consider the errors are in the random read/write functions - they will be the next to test.

[skx]

Fixed. I'd made a backwards test when considering padding.

Everything works now:

A>cc hello 

C Vers. 1.06D 8080  (C) 1982 1983 1984 by Manx Software Systems

A>as hello

8080 Assembler Vers. 1.06D

A>ln hello.o c.lib

C Linker Vers. 1.06D
Base: 0100   Code: 1aec  Data: 01ef  Udata: 0250  Total: 001f30

A>hello

Hello, world

A>type hello.c

/*
 * CC HELLO
 * AS HELLO
 * LN HELLO.O C.LIB
 */
#include "STDIO.H"

main(argc, argv)
int argc;
char *argv[];
{
   printf("Hello, world\n");
   return 0;
}