6 replies to this topic

[bluetriforce]

Hi, I am a newbie with no atari 2600 programming skills, but willing to learn. Right now I am just now learning pre algebra and trying to study binary numbers, and my goal is learn from pre algebra to algebra 2, calculus, binary numbers, binary logic, booleam algebra, and someday to making a atari 2600 game. What I do know about binary numbers is converting decimal numbers to binary and binary to decimal and binary addition. Can someone please explain binary subtraction, and binary negative numbers and binary logic to me.

Thanks for your help!

[Scuttle130]

I tried the 2600 programming, but some of this get pretty thick pretty quick!!! And until Andrew can help us out more, I am at a standstill.

I have been working on programming the 5200 if you want to take a look at my work, its coming along decently. I started programming when I was in 6th grade and picked up BASIC pretty quick. The 5200 language is pretty close with some weird formatting, but still far, far, far easier than figuring out the 2600 programming to start with...

Check out my progress...
http://www.atariage....pic.php?t=44890

[Nukey Shay]

Decimal to binary is simple. You just subtract a power of 2 from each result until you get down to the last 1/0. If the remainder of each result is not high enough to subtract the next lower power of 2, you'd stick a zero in that "bit".

In a single byte, the maximum decimal amount that can be stored is 255 - the value you'd have if all of the "bits" in that byte held a 1 instead of a zero. The binary number %11111111 equals the decimal 128+64+32+16+8+4+2+1. Subtracting a binary value from another binary value works the same way as decimal subraction...you just need to remember that you'd be working with base 2 (only using digits 0 and 1)numbers and not base 10 (using digits 0 to 9).

At least that is how it works when you are treating all of those 256 combinations as positive values.

Since you only have 256 possible combinations, that doesn't leave any room for negative values. The 65xx chip provides a way of using negative values by including instructions that will treat half of those combinations as being positive (decimal values 0 to 127), and the other half negative (decimal values 128-255). This is signified by the state of the leftmost bit. If this bit is zero, the number is positive. When it's 1, the number is negative. And then the remaining bits signify what you would subtract. For example, %01111111 is equal to 64+32+16+8+4+2+1 decimal, or 127... but %11111111 is equal to 64+32+16+8+4+2+1 decimal minus the leftmost bit (128). 127-128= -1.

[Serguei2]

bluetriforce said:

Hi,  I am a newbie with no atari 2600 programming skills, but willing to learn.

I have the same situation than you. I begin to follow Andrew's tutorials.

Now I can draw playgrounds on the 2600. But I still hard learning how to use sprites.


Serguei.

[Mord]

Serguei2 said:

bluetriforce said:

Hi,  I am a newbie with no atari 2600 programming skills, but willing to learn.

I have the same situation than you. I begin to follow Andrew's tutorials.

Now I can draw playgrounds on the 2600. But I still hard learning how to use sprites.

Andrew's tutorials are indeed invaluable, and hopefully he'll get around to finishing them one way or another!

Also consider subscribing to the Stella mailing list and lurk. Watching the big guys go on about the various topics is worth the time, even if it's a bit high traffic at times.

--
Mord

[MrAtari2600_Old]

i really want to know who andrew is and were i can get his tortuals please tell me wer i can get these urls please i would really like to be able to program an atari2600 game please respond someone asap

[Gateway]

MrAtari2600 said:

i really want to know who andrew is and were i can get his tortuals please tell me wer i can get these urls please i would really like to be able to program an atari2600 game        please respond someone asap

You are in the right place. Try this. http://www.atariage....pic.php?t=33233