The **Casio FX-19** is a scientific calculator released in 1976. With dimensions of 89mm x 148mm x 28mm and weighing 180g without batteries, it is a relatively compact and portable device. Power is supplied by 4 AA batteries or through an adapter socket on the side, providing 6V DC at 0.35W.

The case consists of a smooth white plastic base and black front panel. The keyboard is set into a brushed aluminum inset printed with black and tan text. The display is a 10-digit vacuum fluorescent tube, though only 8 digits plus a negative sign are used. Additional display modes support scientific notation with 6 mantissa and 2 exponent digits.

Feature-wise, the FX-19 supports the four basic arithmetic operations along with more advanced scientific functions like fractions, reciprocals, roots, logarithms, trigonometry and statistics. Memory storage is available but with no indication of usage. The calculator can operate in degree, radian or gradian modes for trigonometric calculations.

Internally, the FX-19 utilizes a Hitachi HD36130 microprocessor with a 10-digit VFD display driven by an LD8150 driver IC. The keyboard connects to the main board via a bundle of copper wires. Construction involves removing screws from the back and battery compartment to detach the front panel.

Overall, the FX-19 provides a good range of mathematical capabilities in a compact form factor. However, the limited display precision of only 8 digits makes it less suited for demanding scientific work compared to contemporary competitors. Lack of error recovery from overflow or divide by zero is another drawback. On the plus side, fractional arithmetic is a useful addition not always found at the time. The FX-19 represents an early stage in Casio’s long history of affordable scientific calculators.

Logic notes:

- Clear key removes current number, All Clear resets fully
- Overflow suppressed, 9th digit ignored
- Constant second press of operator for multiply/divide
- No memory use indication
- Negative sign takes 9th digit position
- Overflow shows non-recoverable error
- Divide by zero non-recoverable error
- No negative square roots
- Standard notation 6 digits mantissa, 2 digit exponent
- Can change sign mid-number entry
- Precision limited to 8 digits

The Casio FX-19 provides basic scientific math capabilities in a compact 1976 package. With fraction support but limited precision, it marked an early milestone for Casio in affordable calculators.