Axe Q&A

[Deep Thought]

so i can treat it as a string? is there any way to store the output of "input" directly to a string?

Of course. As long as the input is only capital letters and numbers, it should show up perfectly. If the user inputs other characters, though, they may show up as weird characters.

[willrandship]

He doesn't understand non-OO langs yet. Aka, teach the concept of pointers.

[Deep Thought]

Ah. Well here's a breakdown:

When you get as low-level as Axe, everything's stored as individual bytes. A variable (A-Z and theta) is 2 bytes (in Axe), a floating-poiint number is 9 bytes, etc. Your calculator has 32,768 bytes of RAM for you to work with. They're just stored one after the other, 32,768 in a row. There's no way to tell the bytes apart, so that's why each one is given an address.

Think of it this way: You've got 32,768 houses lined up in a row that look exactly identical. What really matters is what's in each house, which could be a number from 0 to 255. How do you tell them apart? By using addresses. Each address is a number between $8000 and $FFFF, and they all point to a distinct hou-- er, byte. Hence addresses are called pointers

You can literally store anything here, since they're all numbers anyway. You could represent a string as a sequence of bytes; maybe one particular string you need starts at address $C38E and runs to $C390 (three bytes). $C38E would be the pointer that points to the string.

And then since each pointer is just a number, you can store that in a variable too. The input simply asks the user to input a string, stores it to a string structure somewhere in RAM, and returns the pointer to (address of) the string. That's all that input→P does: it gets an input string, stores it somewhere, then stores the pointer to the string into variable P. You can then display the contents of that string by calling Disp P, for example.

(This is because Disp takes a pointer as an argument and displays the string starting at that address. When you do something like "HELLO"→GDB0:Disp GDB0, all that Axe does is stick the bytes of the string "HELLO" into the program memory and define GDB0 as the address of that string.)

Hope that helps (and hope that clears some stuff up for other people, too)!

[willrandship]

Ah. Well here's a breakdown:

When you get as low-level as Axe, everything's stored as individual bytes. A variable (A-Z and theta) is 2 bytes (in Axe), a floating-poiint number is 9 bytes, etc. Your calculator has 32,768 bytes of RAM for you to work with. They're just stored one after the other, 32,768 in a row. There's no way to tell the bytes apart, so that's why each one is given an address.

Think of it this way: You've got 32,768 houses lined up in a row that look exactly identical. What really matters is what's in each house, which could be a number from 0 to 255. How do you tell them apart? By using addresses. Each address is a number between $8000 and $FFFF, and they all point to a distinct hou-- er, byte. Hence addresses are called pointers

You can literally store anything here, since they're all numbers anyway. You could represent a string as a sequence of bytes; maybe one particular string you need starts at address $C38E and runs to $C390 (three bytes). $C38E would be the pointer that points to the string.

And then since each pointer is just a number, you can store that in a variable too. The input simply asks the user to input a string, stores it to a string structure somewhere in RAM, and returns the pointer to (address of) the string. That's all that input→P does: it gets an input string, stores it somewhere, then stores the pointer to the string into variable P. You can then display the contents of that string by calling Disp P, for example.

(This is because Disp takes a pointer as an argument and displays the string starting at that address. When you do something like "HELLO"→GDB0:Disp GDB0, all that Axe does is stick the bytes of the string "HELLO" into the program memory and define GDB0 as the address of that string.)

Hope that helps (and hope that clears some stuff up for other people, too)!

I love pointers sometimes, hate them others. It's useful, and annoying (especially when using disp ), but mostly useful

[Deep Thought]

I like pointers better than references. With pointers you can do anything

[willrandship]

The nice thing about C++ is you can do both

[Binder News]

The nice thing about Java is that because almost everything is a pointer (primitives aren't), you don't need both.

[ralphdspam]

Thanks, Deep Thought!
I wish someone explained it like that when I was first learning Axe.

[ee511]

but how would you store the "input" data to a string? would it be
input->p
copy(p,str1,length(p))

[Freyaday]

How many buffers are there, and how do I use them in Axe?

[aeTIos]

phew... I think 3: L3, L5,L6
L3: I think this is the backbuffer
L5: this is the buffer of the homescreen (where the chars are stored)
L6: this is the buffer for the screen.

You can call the buffers by using the list variables.

[Runer112]

but how would you store the "input" data to a string? would it be
input->p
copy(p,str1,length(p))

Why would you need to copy the string somewhere else? It already exists in RAM at the location pointed to by the output of input. Also, copying the string to a static pointer could be dangerous if the string that the user entered is larger than the space you allocated for the Str1 pointer.

How many buffers are there, and how do I use them in Axe?

There are 3 buffers built into the operating system. L₆ points to one, which is usually treated as the "main" buffer by programmers because that's the buffer the OS treats as the main buffer. This is also the buffer used with Axe's DispGraph by default. Another buffer is pointed to by L₃, which Axe treats as the second buffer for grayscale images. Axe also has the option to use most of its drawing commands to this buffer in addition to the normal L₆, which could be useful whether or not you're using grayscale. The final buffer allocated by the OS is L₁, the last 54 bytes of which are used by the Axe variables by default. However, you can redefine the variables to point somewhere else and then use this whole buffer. And of course, you can always define your own buffers by just allocating 768 bytes of RAM for one. You could do that by adding 768 bytes of data to your program or making a 768-byte appvar.

[aeTIos]

I was partially right, I cee...

[NinjaKnight]

How do I create a program with GetCalc(? I can create appvars just fine, but trying to create a program crashes. (It really just freezes, actually.)

[Darl181]

And speaking of getcalc, did the syntax change by any chance?  b/c in a side program I'm writing GetCalc(Str1,384)→P only works something like a third of the time.
Yes, Str1 is defined, as appvLightSav.

How do I create a program with GetCalc(? I can create appvars just fine, but trying to create a program crashes. (It really just freezes, actually.)

Don't you get the prgm token from the catalog, then type the name of the desired program?