HP-28 series
With HP- 28C (from 1987) and HP- 28S (from 1988 ) two scientific calculators by Hewlett- Packard were called. It is the forerunner of the model series, HP- 39G, HP- 48, HP- 49 and HP- 50th
Some of the key features of the HP- 28C / S:
- It was the first time a computer algebra system (CAS ) is installed, which permits the use of algebraic expressions and symbolic operations, such as deriving of functions Taylor expansions and easy integrations
- Programming in Reverse Polish Lisp ( RPL)
- Calculations are carried out in the Reverse Polish Notation (RPN )
- Any number of stack registers, which record any type of data, expressions in symbolic algebra and programs
- Complex arithmetic functions and matrix, or in combination with each other.
- High accuracy by the BCD arithmetic
In a calculator developed by HP and produced by NEC Electronics HP Saturn processor used.
HP design associated with a folding mechanism, in which both parts of the housing will receive a movement corresponding to the spiral binding of a book. When closed, the controls of the machine are protected. The lid contains an additional alpha-numeric keyboard (see picture, left half) and can be in the open state, both next to the computer are, as well as be completely folded up behind the computer. In the latter position, the usual purely numerical calculations can be performed while the computer as a calculator single width is held in the hand.
The storage capacity of the HP - 28C was only 2048 bytes, and the CPU was working at a processor clock rate of 640 kHz. This model was replaced about a year later by the 28S with 32 kiB permanent storage at 1 MHz, which in turn was until 1992 on the market. Hewlett -Packard put then from 1991 with the HP- 48S a competitor and successor to the HP- 28S on. Users found new ways to synthetic programming the HP -28, a term which arose with the programming of the HP -41 and the discovery and use of undocumented functions and register says.
As a forerunner of the HP -48 ( the first time in 1990 came on the market as HP- 48SX ) of the HP -28 is very similar to this technically. The main differences were:
- The 28 models are not upgradeable
- The infrared interface is only used to send data to the printer. The exchange of programs / data is not possible.
- Reduced storage capacity on the HP - 28C compared to the HP- 48SX
- Smaller display with 137 × 32 pixels ( 4 lines ), with the bottom line disappears when the soft key labels are displayed.
- No real-time clock ( RTC) and alarm functions, only access to the internal clock counter
- Reduced labor rate
A disadvantage of this design is that it is considered beyond repair in defects because of the welded housing.