The fixed-location variable allocation strategy the author mentions is called overlaying or compile-time stack[0]. It's still very much alive today, thanks to architectures like 8051 that are not really stack-friendly (even though they do have a stack).

> The Keil C51 C Compiler works with the LX51 Linker to store function arguments and local variables in fixed memory locations using well-defined names

[0] http://www.keil.com/support/man/docs/bl51/bl51_overlaying.ht...