>> Guess what? You don't. The Sinclairs *only* accepted keywords with the
>> key combinations! The appropriate keywords should be printed on the
>> keyboard. Not until the Spectrum +3 were you finally able to enter
>> keywords in longhand.
I found this a pretty good way to help beginners
in programming - also it was _very_ fast - In fact
I programmed an 'editor' Apple II wich used exactly
the same way than on the ZX.
> O.K. How do I enter programs, then, such as
> 10 CLS
> 20 PRINT "HELLO";
> 30 GOTO 20
> if I can't enter things such as the "hello"?
After entering a keyword that takes parameters, like
Print or Go To the Keyword Cursor [K] changes for
the Character Cursor [C] and you just enter what ever
you want. It will stay this until New Line is pressed.
And with some trick you could even use keywords within
printed strings so save RAM "LET HERCULES GO TO HELL"
is just a 14 Byte string instead of 22 (Send GATES
instead of HERCULES will save another 3 Bytes).
Just try the folowing program:
10 for i = 1 to 255
20 print chr$(i);
30 next i
This worked only because the CPU was interpreting (!)
the 'video' memory and took the representation of a
byte from the character 'generator' for toggeling
the brightnes. If encountering a Basic Token inside
the screen buffer the keyword was generated.
The Video buffer itself was kind of trickey, since
it is only a dynamic buffer - a strem to be interpreted
for display - for every line only as much chars as needed
where stored with an newline as termination, directly
followed by the next line - so an empty screen just consits
of 16 newlines. AFAIR Basic Memory was growing from the
bottom and screen memory from the top, with variable
storage inbetween. this could lees so an out of memory
abortion if to much was printed onscreen.
The CPU based video display is also the reason for
the SLOW and FAST modi - in FAST the CPU uses all
HighRes graphics are also possible via assembler
subroutiens - just stop the ROM routine and generate
your own signal - up to 300x578 interlaced could
be possible - just without a structured display
memory (witch needs an expansion) the generatable
resolution will be more like 200x578.
>> 1K computer, video entirely via TTL logic, Z80A at 3.5MHz. RAM expansion
>> available; 80x50 (I think) character graphics in B&W. Identical to the
>> British Sinclair ZX80 and ZX81, and scads of info are there for the
>> taking on the Web.
Possible to have 2K (just unsolder the 2114s and put in a 6116),
Standard RAM expansion of 16K, but third party modules of 64
and more K, Additional I/O modules, even floppies have been made.
The ZX80 is not 100% compatible.
Gruss
Hans
--
Ich denke, also bin ich, also gut
HRK
Received on Tue Nov 03 1998 - 09:24:41 GMT