Justin Lloyd's Thinkering

Linkers.

They link various bits of code together in to a final piece of executable code.

It’s like chaining and not like chaining.

I get it now!

Linkers take lots of little bits of “almost” ready to run code that the compiler spits out, and stitches them together in to a single piece of code.

A good linker can rearrange the code in memory based on usage, or other needs.

I think I could modify this linker code to dynamically load code from the floppy on-demand, so the program looks like one big piece of compiled code, that is actually too big to fit in memory, and I could just page bits of the code in as I need it.

Sure, it would slow down execution, but I’d keep the pieces of the program loaded that I absolutely need, and only load in that code that I need on occasion.

I could do this with a spell check in a word processing package instead of loading the spell check from ROM where it is stored now.

I could also load extra game levels in as you play through the game.

I figured out how to make the linker generate a program that has a bootstrap piece of code that then loads other parts of the program that are needed to execute.

Right now the linker is hard-coded to break up a large program in to two separate pieces.

I really think this could work for a text adventure game.

I would just load the room description and any special code that only runs in that room, whenever the player goes in to the room.

It could be paged in from floppy when the player enters the room, and then, when the player leaves the room and go somewhere else, the memory gets over-written with code for that new room the player just wandered off too.

I am coming to realise that C is pretty powerful.

Because I can write code very fast.

Much faster than in assembly.

That runs almost as fast.

Or as fast as I need it to for the software I want to write.

And if I am paying by the hour for someone else to write code for me, if the speed of the code is non-critical, I want them to write that code as quickly as possible.

My C compiler for the Beeb works!

Wow!

Wow!

Wow!

It just compiled my test code.

*dances around room*

A linker?

Seriously, who the hell thought that concept up?!?

If computers are so smart how come they cannot figure out how to correctly execute the lousy, buggy code I just wrote?

Progress is both “fast” and “slow” on the C compiler.

This is the first “real compiler” I’ve ever written.

I’ve done a couple of really simple custom languages, and I was able to cobble together a Forth compiler in 6502.

But this is taking my skills to a whole new level.

It is bloody hard.

I’ve got a book, and that’s helping.

And I’ve learned about lexical analysis, and syntactic analysis, and then I got lost at grammars and the tree structure required to figure out what piece of text can be compiled next.

I’m learning C.

It’s a fun little language to work with.

But before I can start really programming in C, I need a C compiler.

And there isn’t one available for the Beeb.

First I have to write a C compiler (in 6502) and then I can start writing C.