System Variable 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 VFP 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 minimum value for ⎕FPC is 53; the maximum value is the largest positive integer 9223372036854775807.

The system default value is 53.

For example,

      ⎕PP←200
      ⎕FPC←53 ⋄ *1x
2.7182818284590450908
      ⎕FPC←64 ⋄ *1x
2.71828182845904523543
      ⎕FPC←128 ⋄ *1x
2.718281828459045235360287471352662497759
      ⎕FPC←256 ⋄ *1x
2.718281828459045235360287471352662497757247093699959574966967627724076630353555
      ⎕FPC←512 ⋄ *1x
2.71828182845904523536028747135266249775724709369995957496696762772407663035354759457138217852516642742746639193200305992181741359662904357290033429526059559

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

2.71828182845904523536028747135266249775724709369995957496696762772407663035354759457138217852516642742746639193200305992181741359662904357290033429526059563073813232862794349076323382988075319525101901157383418793070215408914993488...