Casio fx-990
Brief History
Although solar cells were used in calculators in 1976, but mass production of cheap cells became available in the early 1980s. In addition to four-function calculators, scientific ones were developed with solar cells from 1982: Casio's first fx-900 was continously improved. The 10-digit capacity fx-990 was replaced with fx-991 in 1984.
| Manufacturer: | CASIO Computer Co., Ltd. (Japan) |
| Mfg. date: | 1983 |
| Size: | 6,8×12,7×0,9 cm |
| Weight (ready for operate): | 64 g |
| Type: | scientific |
| Capacity: | 10+2 digits (input/display) 11+2 digits (internal precision) |
| Operating logic: | algebraic |
| Registers: | 2 standard (with saving the pending operation) 1 constant (with saving the pending operation) 6 bracket (with saving the pending operation) 1 memory (with aritmetic) |
| Features: | %calculation with percent +/-change sign (direct entry of negative numbers) RVexchange registers (X-Y) Ffloating-point notation Fixfixed-point notation: the listed decimals can be chosen (0-9) Sciscientific (exponential) notation Engengineering notation a b/callows entry and display of fractions BSbackspace (right-shift) function Sqrsquare root x2square pivalue of pi (3.1415..) can be recalled 1/xreciprocal trigtrigonometrical functions (sin, cos, tan and inverses: arcsin, arccos, arctan) hyphyperbolic functions (sinh, cosh, tanh and inverses: ar sinh, ar cosh, ar tanh) DMS-DDconversion of decimal and sexagesimal numbers logexponential and logarithmical functions (10- and e-base) yxraising to power SDone variable statistics: calculating mean and standard deviation P-Rconverting coordinates between rectangular and polar systems n!factorial |
| Display: | 12 digit LCD |
| Power: | solar cell |
| Test results: | trigonometry:result of sin-1(cos-1(tan-1(tan(cos(sin(60°)))))), reference value: 60. 59.999992349 exponential:result of 0.999160000, reference value (first 14 digits): 3.0068804206375×10-70 3.0068804292-70 |
fx-990
PCB of the fx-990 and the CPU
Inside of the fx-990: the keyboard
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