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Punix

This is a Unix-like operating system for the TI-89 and TI-92+ graphing calculators.

The name "Punix" is a combination of the words "puny" and "Unix". The other explanation for the name is that the "p" stands for "pico", meaning extremely small. Either way, "Punix" is a nicer, more politically-correct name than my other ideas for a name for my system: "Anux" and "Penix". :D

Features

Here are some current and planned features of Punix:

True multi-tasking (preemptive)
Networking
Filesystem in FlashROM
Floating-point emulation
VT100 terminal emulation (difficult with only a 60×20-character screen!)
Emulation of TI-OS, so it can run programs written for TI-OS (this will probably be an application similar to Wine)
And more!

Progress

So far I've implemented the following:

Some working system calls (most of the simple ones)
True multi-tasking (useless, as only the boot-up process runs now)
60×20-character display with a 4×6-pixel font I designed

2006-11-13

I changed the width of size_t from 16 bits to 32 bits. I discovered that the sizeof operator always returns a 32-bit number in TIGCC, and POSIX states that the size_t is an "unsigned integer type of the result of the sizeof operator" (stddef.h). The same applies to ssize_t, except it is signed. This required me to change several pieces of 68k assembly code, since the exact size of a number needs to be in the code. I also had to change sysent.c, which lists every system call and the number of words of arguments each one takes. I also fixed the sizes for some other syscalls that were wrong already (such as setuid, which had a "0" where it should've been "1").
This change is very good news, because I thought that malloc took an int argument, so I was debating whether to make int 16 bits or 32. Since malloc actually takes a size_t argument, I will make int 16 bits.
I implemented screen scrolling for text. Prior to this the function responsible for this (scrollcellup) was a stub, so the screen did not scroll up when text went past the end of the bottom line or there was a new-line on the bottom line. Now the it scrolls as you would expect.
I also changed the text that shows on start-up of the system. Now it displays one of a few different texts (depending on which is uncommented in the source), two of which are ASCII art. :) The ASCII art makes the screen scroll (they are taller than the screen), so I used them to test the scrolling feature.
I've written some more of the standard header files (those that go in /usr/include/ and /usr/include/sys/) to make them more compliant with POSIX. Boy, there are a lot of standard headers in POSIX! Not only that, but some of them cross-reference types in each other, so I had to write quite a few to make the others work right.
I added a little counter to the bottom-right corner of the screen to show the number of times the nextproc function is called. The number is written directly to video memory, so it's read as a binary number (black pixel=1, white pixel=0). It's just a debugging tool anyway, and it won't be in a release version.

Here's a screenshot of this version so far. Notice that I used the "Achtung!" joke warning message. :) The pixels in the bottom-right corner are the counter I mentioned above.

2006-11-15

I've improved the kputchar function, so now it interprets carriage return, horizontal tab, vertical tab, formfeed, and backspace characters correctly. I also improved how it wraps at the end of the line: now it wraps to the next line only before a printable character or a tab. This means the screen can display a whole line of characters (60 characters wide), and a newline at the end will not add an extraneous blank line.
I also added a horizontal line to show the bottom of the text screen.

Here's a new screenshot. This has text I used for testing the new features of the text screen. Some of the lines have tabs and backspaces in different combinations: