Info Catalog calc: Help Commands calc: Introduction calc: Numeric Entry

calc: Stack Basics

 
 4.3 Stack Basics
 ================
 
 Calc uses RPN notation.  If you are not familiar with RPN, RPN
 Tutorial.
 
    To add the numbers 1 and 2 in Calc you would type the keys: ‘1 <RET>
 2 +’.  (<RET> corresponds to the <ENTER> key on most calculators.)  The
 first three keystrokes “push” the numbers 1 and 2 onto the stack.  The
 ‘+’ key always “pops” the top two numbers from the stack, adds them, and
 pushes the result (3) back onto the stack.  This number is ready for
 further calculations: ‘5 -’ pushes 5 onto the stack, then pops the 3 and
 5, subtracts them, and pushes the result (-2).
 
    Note that the “top” of the stack actually appears at the _bottom_ of
 the buffer.  A line containing a single ‘.’ character signifies the end
 of the buffer; Calculator commands operate on the number(s) directly
 above this line.  The ‘d t’ (‘calc-truncate-stack’) command allows you
 to move the ‘.’ marker up and down in the stack; Truncating the
 Stack.
 
    Stack elements are numbered consecutively, with number 1 being the
 top of the stack.  These line numbers are ordinarily displayed on the
 lefthand side of the window.  The ‘d l’ (‘calc-line-numbering’) command
 controls whether these numbers appear.  (Line numbers may be turned off
 since they slow the Calculator down a bit and also clutter the display.)
 
    The unshifted letter ‘o’ (‘calc-realign’) command repositions the
 cursor to its top-of-stack “home” position.  It also undoes any
 horizontal scrolling in the window.  If you give it a numeric prefix
 argument, it instead moves the cursor to the specified stack element.
 
    The <RET> (or equivalent <SPC>) key is only required to separate two
 consecutive numbers.  (After all, if you typed ‘1 2’ by themselves the
 Calculator would enter the number 12.)  If you press <RET> or <SPC>
 _not_ right after typing a number, the key duplicates the number on the
 top of the stack.  ‘<RET> *’ is thus a handy way to square a number.
 
    The <DEL> key pops and throws away the top number on the stack.  The
 <TAB> key swaps the top two objects on the stack.  Stack and
 Trail, for descriptions of these and other stack-related commands.
 

Info Catalog calc: Help Commands calc: Introduction calc: Numeric Entry