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# Predefined constants

* `byte nullchar` – the null terminator for strings in the default encoding, equivalent to `""z[0]`, can be overriden by the `NULLCHAR` feature

* `byte nullchar_scr` – the null terminator for strings in the screen encoding, equivalent to `""scrz[0]`, can be overriden by the `NULLCHAR_SCR` feature

* `null$ nullptr` – the invalid pointer value; the value of the `NULLPTR` feature

* `bool true`, `bool false` – boolean constants

* `pointer segment.N.start` – the value of `segment_N_start` from the platform definition

* `pointer segment.N.codeend` – the value of `segment_N_codeend` from the platform definition

* `pointer segment.N.datastart` – the value of `segment_N_datastart` from the platform definition

* `pointer segment.N.end` – the value of `segment_N_end` from the platform definition

* `pointer segment.N.heapstart` – the address of the first byte in the `N` segment that was not automatically allocated

* `word segment.N.length` – the number of byte locations between `segment_N_start` and `segment_N_end`, inclusive

* `byte segment.N.bank` – the value of `segment_N_bank` from the platform definition

* `byte segment.N.fill` – the value of `segment_N_fill` from the platform definition