TI SR-50
Encyclopedia
The SR-50 was Texas Instruments
' first scientific pocket calculator
with trigonometric and logarithm
functions. It enhanced their earlier SR-10 and SR-11 calculators, introduced in 1973, which had featured scientific notation
, squares, square root
, and reciprocals, but had no trig or log functions. The SR-50 was introduced in 1974 and sold for US$170. An unusual feature of the SR-50 was that its functions included the hyperbolic trig functions sinh, cosh, and tanh and their inverses, which were found on very few calculators (including the HP-35 and HP-45) at the time. The user invoked the hyperbolic functions by entering the function argument and then pressing the "hyp" key, followed by the "sin", "cos", or "tan" function key. The inverse hyperbolic functions were accessed by first pressing the "arc" and "hyp" keys (in any order) and then pressing the "sin", "cos", or "tan" key. Hyperbolic trig arguments were always assumed to be in radians regardless of the setting of the degree/radian (D/R) mode switch. In addition to its three-register operational stack, consisting of X, Y, and Z registers, the SR-50 also included one memory (M) register to which the value in the X (display) register could be directly added using the "summation" key.
The SR-50 had a red LED display with a signed ten digits mantissa plus a signed two digit exponent for floating point
numbers (negative values were indicated with a leading minus sign and positive values with no sign). Internally, calculations were performed with a 13-digit mantissa
, providing much greater calculation accuracy than the 10-digit precision of most scientific calculators of the time. After the leading sign, digits consisted of 7 segments plus decimal point. A blinking display indicated an error, such as a calculation error or an overflow or underflow condition. Like most scientific calculators, the SR-50 used ordinary infix notation
, as opposed to the postfix reverse Polish notation
employed by its competitor, the Hewlett Packard HP-35
. The SR-50 followed the standard order of operations by performing unary (single-argument) operations (reciprocal, square, square root, log, trig and hyperbolic trig functions) immediately, and multiplication, division, root, and power operations before addition and subtraction operations. As an example, the keypresses to calculate "3 x log(4) + 5" was entered almost as written, namely "3 x 4 log + 5 =". This is because the calculator would execute the log function before performing the multiplication operation, and complete the multiplication operation before executing the addition operation. It did so by having unary operations operate on the X register, addition and subtraction operate on the X and Z registers, and multiplication, division, power, and root functions operate on the X and Y registers in its operational stack.
The SR-50 measured 5-3/4 inches long by 3-1/8 inches wide by 1-3/16 inches high (147 mm by 78 mm by 31 mm) and was powered by a rechargeable NiCad battery pack, built from three soldered AA cells. It had 40 keys, and flat sliding switches for degrees/radian
s and on/off. "SR" stood for "slide rule
."
The SR-50 was followed by the more advanced model SR-51. The SR-51 had the same physical dimensions but added a 2nd function for most buttons. Most notable among the added functions were the ability to enter x:y pairs and do linear regression analysis on them. The later and lighter versions SR-50A and SR-51II and SR-51III were based on smaller ICs and battery packs and reached broadest distribution.
A further update resulted in the programmable model SR-52
in late 1975. It was thicker and longer and could perform 224 program steps recorded on magnetic cards, similar to its competitor HP-65
. The card was pulled through the reader by an electric motor. The matte white upper face of the cards could be marked with pen or pencil to indicate the program and the functions assigned to the calculator's programmable keys. The card could be stored in a slot above the programmable keys with its markings visible.
In 1976 Texas Instruments released the TI-30
budget calculator at one-third the price of the SR-50, so sales of the SR-50 quickly dropped.
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
' first scientific pocket calculator
Calculator
An electronic calculator is a small, portable, usually inexpensive electronic device used to perform the basic operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.The first solid-state electronic...
with trigonometric and logarithm
Logarithm
The logarithm of a number is the exponent by which another fixed value, the base, has to be raised to produce that number. For example, the logarithm of 1000 to base 10 is 3, because 1000 is 10 to the power 3: More generally, if x = by, then y is the logarithm of x to base b, and is written...
functions. It enhanced their earlier SR-10 and SR-11 calculators, introduced in 1973, which had featured scientific notation
Scientific notation
Scientific notation is a way of writing numbers that are too large or too small to be conveniently written in standard decimal notation. Scientific notation has a number of useful properties and is commonly used in calculators and by scientists, mathematicians, doctors, and engineers.In scientific...
, squares, square root
Square root
In mathematics, a square root of a number x is a number r such that r2 = x, or, in other words, a number r whose square is x...
, and reciprocals, but had no trig or log functions. The SR-50 was introduced in 1974 and sold for US$170. An unusual feature of the SR-50 was that its functions included the hyperbolic trig functions sinh, cosh, and tanh and their inverses, which were found on very few calculators (including the HP-35 and HP-45) at the time. The user invoked the hyperbolic functions by entering the function argument and then pressing the "hyp" key, followed by the "sin", "cos", or "tan" function key. The inverse hyperbolic functions were accessed by first pressing the "arc" and "hyp" keys (in any order) and then pressing the "sin", "cos", or "tan" key. Hyperbolic trig arguments were always assumed to be in radians regardless of the setting of the degree/radian (D/R) mode switch. In addition to its three-register operational stack, consisting of X, Y, and Z registers, the SR-50 also included one memory (M) register to which the value in the X (display) register could be directly added using the "summation" key.
The SR-50 had a red LED display with a signed ten digits mantissa plus a signed two digit exponent for floating point
Floating point
In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...
numbers (negative values were indicated with a leading minus sign and positive values with no sign). Internally, calculations were performed with a 13-digit mantissa
Mantissa
* The mantissa is the significand in a common logarithm or floating-point number.* Metaphorically, it is the part of the self that eludes conscious awareness or self-understanding.* An addition of little importance.Mantissa may also refer to:...
, providing much greater calculation accuracy than the 10-digit precision of most scientific calculators of the time. After the leading sign, digits consisted of 7 segments plus decimal point. A blinking display indicated an error, such as a calculation error or an overflow or underflow condition. Like most scientific calculators, the SR-50 used ordinary infix notation
Infix notation
Infix notation is the common arithmetic and logical formula notation, in which operators are written infix-style between the operands they act on . It is not as simple to parse by computers as prefix notation or postfix notation Infix notation is the common arithmetic and logical formula notation,...
, as opposed to the postfix reverse Polish notation
Reverse Polish notation
Reverse Polish notation is a mathematical notation wherein every operator follows all of its operands, in contrast to Polish notation, which puts the operator in the prefix position. It is also known as Postfix notation and is parenthesis-free as long as operator arities are fixed...
employed by its competitor, the Hewlett Packard HP-35
HP-35
The HP-35 was Hewlett-Packard's first pocket calculator and the world's first scientific pocket calculator . Like some of HP's desktop calculators it used reverse Polish notation. Introduced at US$395, the HP-35 was available from 1972 to 1975.Market studies at the time had shown no market for...
. The SR-50 followed the standard order of operations by performing unary (single-argument) operations (reciprocal, square, square root, log, trig and hyperbolic trig functions) immediately, and multiplication, division, root, and power operations before addition and subtraction operations. As an example, the keypresses to calculate "3 x log(4) + 5" was entered almost as written, namely "3 x 4 log + 5 =". This is because the calculator would execute the log function before performing the multiplication operation, and complete the multiplication operation before executing the addition operation. It did so by having unary operations operate on the X register, addition and subtraction operate on the X and Z registers, and multiplication, division, power, and root functions operate on the X and Y registers in its operational stack.
The SR-50 measured 5-3/4 inches long by 3-1/8 inches wide by 1-3/16 inches high (147 mm by 78 mm by 31 mm) and was powered by a rechargeable NiCad battery pack, built from three soldered AA cells. It had 40 keys, and flat sliding switches for degrees/radian
Radian
Radian is the ratio between the length of an arc and its radius. The radian is the standard unit of angular measure, used in many areas of mathematics. The unit was formerly a SI supplementary unit, but this category was abolished in 1995 and the radian is now considered a SI derived unit...
s and on/off. "SR" stood for "slide rule
Slide rule
The slide rule, also known colloquially as a slipstick, is a mechanical analog computer. The slide rule is used primarily for multiplication and division, and also for functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction.Slide rules come in a...
."
The SR-50 was followed by the more advanced model SR-51. The SR-51 had the same physical dimensions but added a 2nd function for most buttons. Most notable among the added functions were the ability to enter x:y pairs and do linear regression analysis on them. The later and lighter versions SR-50A and SR-51II and SR-51III were based on smaller ICs and battery packs and reached broadest distribution.
A further update resulted in the programmable model SR-52
TI-59
The TI-59 was an early programmable calculator, manufactured by Texas Instruments from 1977. It was the successor to the TI SR-52, quadrupling the number of "program steps" of storage, and adding "ROM Program Modules" and a magnetic card reader for external storage...
in late 1975. It was thicker and longer and could perform 224 program steps recorded on magnetic cards, similar to its competitor HP-65
HP-65
The HP-65 was the first magnetic card-programmable handheld calculator. Introduced by Hewlett-Packard in 1974 at an MSRP of $795, it featured nine storage registers and room for 100 keystroke instructions. It also included a magnetic card reader/writer to save and load programs...
. The card was pulled through the reader by an electric motor. The matte white upper face of the cards could be marked with pen or pencil to indicate the program and the functions assigned to the calculator's programmable keys. The card could be stored in a slot above the programmable keys with its markings visible.
In 1976 Texas Instruments released the TI-30
TI-30
The TI-30 was a scientific calculator manufactured by Texas Instruments, the first model of which was introduced in 1976. While the original TI-30 left production in 1983 after several design revisions, TI maintains the TI-30 designation as a branding for its low and mid-range scientific...
budget calculator at one-third the price of the SR-50, so sales of the SR-50 quickly dropped.