tau is a fast RPN scientific command line math tool with array processing, complex number support, matrix math, unit conversions, built-in help, logic operations, statistics, signal processing, and other advanced functions.

• Reverse Polish Notation, or postfix, refers to the work of Polish logician Jan Łukasiewicz. Its primary advantage is minimal keystrokes, and it quickly becomes intuitive.

• Arguments are entered first, followed by the operator or function that uses them. Parentheses are not used. Think of the operands as cafeteria trays that are pushed onto a stack. Functions pop the requisite number of trays off of the stack again.

• The operands can be combined onto one line, separated by spaces. Numbers may be entered in standard scientific notation: 6.02E23

• Examples of tau syntax: 1 1 +, deg 45 sin, 3 2 ^ 4 2 ^ + sqrt

• The ↑↓ keys scroll through past input.

• The operators are: + - * / ! ^ % ? = Y= , ~ []

• The = operator is used to name a soft constant. E.g., '1.23 x ='. 'x' may then be used as a variable.

• Every function in tau has built-in help: 'cosh?'.

• Unit conversions: e.g., '1 inch cm' yields '1 inch = 2.54 cm'.

• 'convert' lists the categories. Or enter a category name ('area') to list all its units.

• 'consts' lists all predefined physical constants.

• '?' lists all available functions.

• 'stack' (alias 'stk') shows the contents of the stack.

• 'bin', 'dec', or 'hex' put tau in logic mode for bit manipulation functions.

• Arrays. Beginning a line with '~' will treat that line's functions for an entire array. For example, '~cos' will compute the cosine over the entire X array (arx).

• There are two scratchpad arrays: X and Y. X is the primary one. Y may be used to hold values that depend on those of X. For example, we may have data acquisition times in array X, and temperatures in Y.

• 'arx' lists the contents of the X array; 'ary' lists Y. You may name arx using '~SomeName='.

• The duple operator ',' (comma) is useful for making quick two-dimensional ordered-pair arrays. For each pair enter the independent variable x first, then the dependent one y. For example, to calculate a linear regression of temperature data for three sample times, enter

  ~10 25.4, 11 25.8, 12 30.1, fitlin

• 'mtx?' yields help on matrix syntax.

• Complex numbers are easy in tau. The syntax is 'a±bi ' (argand format) without any space. Alternatively, you may say 'ρ<θ ', where ρ is the modulus and θ the phase angle. This is referred to as phasor notation. Many tau functions operate over the complex domain.

Available on disk or USB Flash drive.  Specify on order.