To: J3                                                     J3/18-120r2
From: Steve Lionel
Subject: Control of leading zero in F and E format
Date: 2018-February-13

Reference: 18-007

When using F format to output a value less than 1, the standard
allows the implementation to choose whether to include a
zero before the decimal symbol.

13.7.2.3.2 (F format) paragraph 11 says (in part):

"Leading zeros are not permitted except for an optional zero
immediately to the left of the decimal symbol if the magnitude
of the value in the output field is less than one. The optional
zero shall appear if there would otherwise be no digits in the
output field."

Similarly for E format, when the scale factor is zero, 13.7.2.3.2p11
says:

"Leading zeros are not permitted except for an optional zero
immediately to the left of the decimal symbol if the magnitude of the
value in the output field is less than one. The optional zero shall
appear if there would otherwise be no digits in the output field."

EN, ES and EX formats do not have this option.

Some implementations always provide the leading zeros, some do
not, and this inconsistency results in user complaints, especially
when test programs produce different results across different
implementations. The inconsistency also occurs for G format when
the value is in a certain range, since E and F formatting is used.

Unlike the optional sign before a positive value, there is no
user control over the optional zero.

The proposal is to add control edit descriptors, analogous to the
SS, SP and S edit descriptors, allowing the programmer to specify
the desired behavior. Proposed:

  ZN - No leading zero
  ZS - Supply leading zero
  ZP - Processor-defined behavior

The requirement of the leading zero when otherwise no digits would
appear is to remain.

Continuing the analogy with SS, SP and S, and the SIGN= OPEN/INQUIRE
specifier, a ZERO= OPEN and INQUIRE specifier would be added with
possible values of 'NO', 'SUPPLY', and 'PROCESSOR_DEFINED'.
The default would be 'PROCESSOR_DEFINED'.