A question about BBC/Electron bit-pairs

[José Pereira]

Hi.

Starting explaining why I posted here and not on the Programming forum because for sure more people will see and is also A8 related because of things I have in mind and for future stuff.

On most of their games 160x wide screen they're in 4colours 2bpp (because it takes half of the 4bpp and their memory of only 32Kbs wouldn't have much for the game code) that is a similar to ours bitmap mode GR.15 and is usually 3colours more black and the black is also on the borders.

Seeing this can I be sure that like ours BAK colour register that is also on them black is always (00) inside the game area and on the borders?

Thanks.

 

P.s.- By the way and for curiosity are there any games on Beebs that have any other colour or they're restricted to in all/always have black on borders?

I can't seem to remember, find or ever see any game, demo or program that has other than black borders.

[Rybags]

BBC has 16 colour registers. Border colour as far as I can deduce will always be black. Also note modes with blank space mentioned later.

You can set the colour registers to any of the 8 possible RGB based colours, there's also facility for blinking colour settings with variable time between each of the 2 colours.

 

Also, the bitmapping method is like the C64 - cell based rather than linear.

Note also - there are no text modes with character sets as such. The only true character mode is MODE 7, the Teletext mode. It has predefined characters and chunky shapes and attribute bytes but doesn't lend to graphical games well.

Even though you can edit programs in MODES 0 thru 6, they are in fact bitmap modes with the characters rendered by the OS. Not all the modes are useful as bitmap modes either as some have blank space between each character line (modes 3 and 6).

Edited January 20, 2017 by Rybags

[José Pereira]

Thanks that what I thought and if you go to the 2bpp that is 4colours out of those 8.

One game I'm am looking has screen colours black, red, green and yellow and soft sprites black, red and yellow.

The soft sprites were the reason for my question because I was almost sure that they weren't masking having them (00). Now I am sure they have the more common and simplier/faster to code on all computers (01)/(10)/(11) while green (00) is on the background, the transparent colour.

It was the black also on the borders that make me to have doubts.

Yeah, this is different from us.

Edited January 20, 2017 by José Pereira