I found this in Sinclair User, it works on a real zeddy so it should also work on an emulator. Does anyone know how it does it?
Here it is as written....
"Here is a way you can use NEW and OLD statements on the 16k ZX-81 in a similar way to the BBC computer:
Load or type in a program on your ZX-81.
To NEW the program,type POKE 16509,100 (newline). this, seemingly, will NEW the program.
To retrieve POKE 16509,0 (newline). This may be useful if You are playing a game or writing a program and You have to interrupt it to write a small program - to total Your shopping list, for example.
It is important to delete Your shopping list program or whatever without using NEW before attempting to retrieve the original program."
Would love to know the answer!!
I don't know anything about BBC computer, but
POKEing 16509 with 100 will rise the numer of the first BASIC-line up to 25600 or more, depending on the contensts of 16510, much more than ZX81 can display, because only 4 digits are reserved to display the line number. Maximum will be 9999
In 16509 you will find the most significant byte of the line number, in 16510 the less significant byte.
After that you can type in BASIC lines with low line numbers for some tests e.g.
You must delete these lines line by line before you continue with the old programm with POKE 16509, 0