Design Sinclair Scientific

1 design

1.1 sinclair scientific

1.1.1 assembly kit
1.1.2 giant scientific


1.2 sinclair scientific programmable
1.3 calculations using sinclair scientific

design
sinclair scientific

the hp-35 used 5 chips, , had been developed twenty engineers @ cost of million dollars, leading texas instruments engineers think sinclair s aim build scientific calculator around tms0805 chip, barely handle four-function arithmetic, impossible. however, sacrificing speed , accuracy, sinclair used clever algorithms run scientific operations on chip room 320 instructions. constants, rather being stored in calculator, printed under screen.

it displays in scientific notation, 5 digit mantissa , 2 digit exponent, although sixth digit of mantissa stored internally. because of way processor designed, uses reverse polish notation (rpn) inputting calculations. rpn meant difficult implementation of brackets, , associated recursive logic, not necessary implement in hardware, effort instead offloaded user. instead of equals button, there enter button tells calculator when value has been entered, , operators entered in after operands. example, on devices evaluate (1+2) x 3 , sequence entered 3 enter 2 enter 1 + x. sinclair scientific entry procedure different lacks enter key , has limited number of internal registers.

to fit program 320 words available on chip, significant modification used. not using regular floating point numbers, require lots of instructions keep decimal point in right place, space freed up. trigonometric functions implemented in 40 instructions, , inverse trigonometric functions 30 more instructions. logarithms 40 instructions, anti-log 20 on top of that. code normalize , display computed values same in both ti , sinclair programs.

the design of algorithms meant calculations, such arccos0.2, take 15 seconds, whereas hp-35 designed complete calculations in under second. accuracy in scientific functions limited around 3 digits @ most, , there number of bugs , limitations.

ken shirriff, employee of google, reverse engineered sinclair scientific , built simulator using original algorithms.

assembly kit

the assembly kit consisted of 8 groups of components, plus carry case. build time advertised being around 3 hours, , required soldering iron , pair of cutters. in january 1975, kit available us$49.95, half price @ time of introduction year earlier, , in december 1975 available gb£9.95, less quarter of introductory price.

giant scientific

a version of scientific, same functionality, made 30 68 centimetres (12 in × 27 in), , known giant scientific. powered 240v ac, , used discrete leds display.

sinclair scientific programmable

the sinclair scientific programmable introduced in 1975, same case sinclair oxford. larger scientific, @ 73 155 34 millimetres (2.9 in × 6.1 in × 1.3 in), , used larger pp3 battery, powered mains electricity.

it had 24-step programming abilities, meant highly limited many purposes. lacked functions natural logarithm , exponential function. constants used in programs required integers, , programming wasteful, start , end quotes needed use constant in program.

however, included calculator library of on 120 programs performed common operations in mathematics, geometry, statistics, finance, physics, electronics, engineering, fluid mechanics , materials science. full library of standard programs contained on 400 programs in sinclair program library.

calculations using sinclair scientific

the sinclair used different reverse polish notation method; lacking enter key, operation keys enter number appropriate register , calculation performed. example, (1+2) * 3 calculated as: c 1 + 2 + 3 × give result of 9.0000 00 (7000900000000000000♠9.0000×10, or 9). c key performs clear; pressing sets calculator state 0 in internal registers. pressing c followed number keys + adds number entered 0 , stores internally worked on in subsequent calculations. if - key pressed instead, number subtracted zero, entering negative number.

all numbers entered in scientific notation. after entering mantissa part of number e exponent key pressed prior entering integer exponent of number. respect order of operations placed on user, , there no bracket keys. display shows 5 digits, 6 digits can entered. example 12.3*(-123.4+123.456) entered c 1 2 3 4 e 2 - 1 2 3 4 5 6 e 2 + 1 2 3 e 1 × displayed result of 6.8880 -01 (representing 6999688800000000000♠6.8880×10, or 0.68880).

four constants printed on calculator case easy reference. converting , base 10 logarithms , natural logarithms natural logarithm of 10 (2.30259) , e (2.71828) printed on case. pi (3.14159) , 57.2958 (180 / pi) on case trigonometry calculations. there not enough internal memory store these constants internally. angles computed using radians; degree values must converted radians dividing 57.2958. example, calculate 25 sin (600*0.05°) 1 enter c 6 e 2 + 0 0 5 × 5 7 2 9 5 8 e 1 ÷ ▲ + 2 5 e 1 × result of 1.2500 01 (representing 12.5 equal 25 sin(30°) ). sine selected combination of ▲ key followed + key. ▼ (down) , ▲ (up) arrow keys function select keys. 4 operation keys ( -, +, ÷ , × ) have 2 other function activated using 1 of arrow keys. function available sine, arcsine, cosine, arccosine, tangent, arctangent, logarithm , antilogarithm.