System Variable FPC

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⎕FPC - Floating Point Control

Z←⎕FPC returns the current value of the Floating Point Control precision.
Z is an integer scalar that represents the current value of the number of bits of precision used for Multiple-Precision Floating Point numbers.


⎕FPC←R sets the value of the Floating Point Control precision to R.
⎕FPC←⍬ sets the value of the Floating Point Control precision to its system default state.


The approximate number of digits of precision for a given value of ⎕FPC is about 10⍟2*⎕FPC. The value of ⎕FPC for a given required precision is about ⌈2⍟10*digits.

The minimum value for ⎕FPC is 1; the maximum value is the integer 1073741695 ←→ ¯129+2*30 ←→ 16b3FFFFF7F.

The system default value is 128.


For example:

        ⎕PP←240 
        ⎕FPC←64   ⋄ *1x
  2.7182818284590452354 
        ⎕FPC←128  ⋄ *1x
  2.71828182845904523536028747135266249776 
        ⎕FPC←256  ⋄ *1x
  2.71828182845904523536028747135266249775724709369995957496696762 
➥      772407663035355
        ⎕FPC←512  ⋄ *1x
  2.71828182845904523536028747135266249775724709369995957496696762
➥      7724076630353547594571382178525166427427466391932003059921
➥      8174135966290435729003342952605956 
        ⎕FPC←1024 ⋄ *1x
  2.71828182845904523536028747135266249775724709369995957496696762
➥      7724076630353547594571382178525166427427466391932003059921
➥      8174135966290435729003342952605956307381323286279434907632
➥      3382988075319525101901157383418793070215408914993488416750
➥      924

Whereas, according to Wolfram Alpha, the exact value to 230 digits is

  2.71828182845904523536028747135266249775724709369995957496696762
➥      7724076630353547594571382178525166427427466391932003059921
➥      8174135966290435729003342952605956307381323286279434907632
➥      3382988075319525101901157383418793070215408914993488...

See Also: Comparison Tolerance ⎕CT


System Variables (A value may be assigned to these except for ⎕DM)
⎕ALX ⎕CT ⎕DM ⎕DT ⎕ELX ⎕FC ⎕FEATURE ⎕FPC ⎕IC ⎕IO
⎕LR ⎕LX ⎕PP ⎕PR ⎕PW ⎕RL ⎕SA ⎕WSID
Niladic System Functions (a value cannot be assigned to these)
⎕A ⎕AV ⎕EM ⎕ET ⎕LC ⎕NNAMES ⎕NNUMS ⎕SI ⎕SYSID ⎕SYSVER
⎕T ⎕TC ⎕TCBEL ⎕TCBS ⎕TCESC ⎕TCFF ⎕TCHT ⎕TCLF ⎕TCNL ⎕TCNUL
⎕TS ⎕WA
Monadic or dyadic system functions (a value cannot be assigned to these)
⎕AT ⎕CR ⎕DC ⎕DFT ⎕DL ⎕DR ⎕EA ⎕EC ⎕ERROR ⎕ES
⎕EX ⎕FMT ⎕FX ⎕MF ⎕NAPPEND ⎕NC ⎕NCREATE ⎕NERASE ⎕NINFO ⎕NL
⎕NLOCK ⎕NREAD ⎕NRENAME ⎕NREPLACE ⎕NRESIZE ⎕NSIZE ⎕NTIE ⎕NUNTIE ⎕STOP ⎕TF
⎕TRACE ⎕UCS ⎕VR
Note that quad functions and variables (except for the ⎕A family of functions) are case insensitive


See Also
System Commands System Variables and Functions Operators


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