/usr/share/calc/help/base is in apcalc-common 2.12.4.4-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 | NAME
    base - set default output base
SYNOPSIS
    base([mode])
TYPES
    mode	real
    return	real
DESCRIPTION
    The base function allows one to specify how numbers should be
    printed.  The base function provides a numeric shorthand to the
    config("mode") interface.  With no args, base() will return the
    current mode.  With 1 arg, base(val) will set the mode according to
    the arg and return the previous mode.
    The following convention is used to declare modes:
	     base	equivalent
		      config("mode")'s
	       2	"binary"	base 2 fractions
			"bin"
	       8	"octal"		base 8 fractions
			"oct"
	      10	"real"		base 10 floating point
			"float"
			"default"
	     -10	"integer"	base 10 integers
			"int"
	      16	"hexadecimal"	base 16 fractions
			"hex"
	     1/3	"fraction"	base 10 fractions
			"frac"
	    1e20	"scientific"	base 10 scientific notation
			"sci"
			"exp"
    For convenience, any non-integer value is assumed to mean base 10
    fractions and any integer >= 2^64 is assumed to mean base 10
    scientific notation.
    These base() calls have the same meaning as config("mode", "fraction"):
	base(1/3)	base(0.1415)	base(16/37)
    These base() calls have the same meaning as config("mode", "scientific"):
	base(1e20)	base(2^64)	base(2^8191-1)
    However the base() function will only return one of the base values
    listed in the table above.
EXAMPLE
    ; base()
	    10
    ; base(8)
	    012
    ; print 10
    012
LIMITS
    none
LINK LIBRARY
    int math_setmode(int newmode)
    NOTE: newmode must be one of MODE_DEFAULT, MODE_FRAC, MODE_INT,
	  MODE_REAL, MODE_EXP, MODE_HEX, MODE_OCTAL, MODE_BINARY
SEE ALSO
    base2, config, str
## Copyright (C) 1999  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
##
## @(#) $Revision: 30.1 $
## @(#) $Id: base,v 30.1 2007/03/16 11:10:42 chongo Exp $
## @(#) $Source: /usr/local/src/cmd/calc/help/RCS/base,v $
##
## Under source code control:	1994/09/30 00:09:39
## File existed as early as:	1994
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/
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