Where is Sys.init defined?

[Henoktes722]

In the bootstrap code,

SP=256
call Sys.init

I know that Sys.init calls the main function of the program to start executing of our program. But I can't say it is already defined, because we are actually build the computer from down, so we know what things had so far. If it is not a primitive, how can I create this function, the logic of finding and executing the main method?

[WBahn]

Sys.init() is simply a function that is compiled just like any other Jack code.

The trick isn't how Sys.init() finds the Main.main() function, it simply calls it just like any other piece of Jack code calls any other function.

The trick is how Sys.init() gets called. That is the role of the bootstrap code that is put at the beginning of the .asm file by the VM translator.

[Henoktes722]

So do I need to define the function or it's a primitive?

[WBahn]

Henoktes722 wrote

So do I need to define the function or it's a primitive?

Eventually you will write that function as part of the operating system. But for now it is supplied. Read the description of the test programs for the function calling commands (p171 of the text).

[Henoktes722]

Sure, I'll definitely check it.