ELF II
The Netronics ELF II was an early microcomputer trainer kit featuring the RCA 1802 microprocessor, 256 bytes of RAM, DMA-based bitmap graphics, hexadecimal keypad, two digit hexadecimal LED display, a single "Q" LED, and 5 expansion slots. The system was developed and sold by Netronics Research and Development Limited in New Milford, CT, USA.

Hardware 
Available hardware accessories included:
 The "Giant Board" (ROM monitor, serial and parallel I/O, Cassette interface)
 4KB and 16KB (static) RAM boards
 ASCII Keyboard 
 Video display card (monochrome text)
 Low resolution color graphics board
 "Full BASIC" board with BASIC preloaded in ROM chips
 EPROM burner board
 External Power Supply
 Attractive, heavy duty metal cases for the CPU, keyboard, and power supply

Software
Available software included:
 6800 Tiny BASIC (integer BASIC interpreter)
 Text Editor
 Full BASIC (floating point BASIC interpreter using Reverse Polish Notation)

Notable Innovations
 Unlike similar "bare circuit card" trainer/experimenter computers of the day, the ELF II could be easily expanded thanks to its built-in bus. 
 The video card is mounted underneath the keyboard inside the metal case. This allows it to be used as a standalone computer terminal if needed.
 The Elf II used a simple and low-cost math coprocessor. The "Full BASIC" ROM card contained an RPN calculator chip.  As a result, floating point operations were an order of magnitude faster than what was possible in software. However, the BASIC syntax for math was non-standard as it used postfix RPN (see code example below). Historically, this was also the heyday of Hewlett Packard calculators, so it was a fair bet that any technically minded person willing to assemble a computer either already knew RPN or could easily learn it and adapt.

10 REM This program will print the number 30
20 A=10,B=20
30 C=A#B+
40 PRINT C
50 END
In the code above, the "#" symbol is equivalent to the "Enter" key on a RPN calculator.

The Name 
The ELF part of the name came from an earlier machine called the "COSMAC ELF", published as a construction project in Popular Electronics magazine. Improvements on its predecessor included an etched PCB, a hexadecimal keypad instead of toggle switches for program entry, the CDP1861 Pixie-graphics chip, and the 5 slot 86-line bus for expansion cards.

See also
COSMAC ELF
RCA COSMAC VIP
Quest SuperELF
RCA 1802 microprocessor
Early Microcomputers
Competing 6502 microprocessor based trainers KIM-1 and Rockwell AIM-65
8080 Based machines: MITS Altair 8800 and IMSAI 8080
RCA Studio II

References

External links 
 

Early microcomputers