ISO/FDIS 25178-71

Geometrical product specifications (GPS) — Surface texture: Areal — Part 71: Surface data file (SDF) file format

ISO 25178-71:2017 defines Type S1 and Type S2 software measurement standards (etalons) for verifying the software of measuring instruments. It also defines the file format of Type S1 software measurement standards for the calibration of instruments for the measurement of surface texture by the areal method as defined in the areal surface texture chain of standards, chain link G. NOTE Throughout ISO 25178-71:2017, the term "softgauge" is used as a substitute for "software measurement standard Type S1".

Spécification géométrique des produits (GPS) — État de surface: Surfacique — Partie 71: Format de fichier de surface (SDF)

L'ISO 25178-71:2017 définit les étalons logiciels de Types S1 et S2 qui permettent de vérifier les logiciels des instruments de mesure. Il définit également le format de fichier des étalons logiciels de Type S1 utilisés pour l'étalonnage des instruments de mesure d'état de surface, conformément à la méthode surfacique telle que définie dans le maillon G de la chaîne de normes sur l'état de surface surfacique. NOTE Dans l'ISO 25178-71:2017, le terme «étalon logiciel» désigne un «étalon logiciel de Type S1».

General Information

• Status: Not Published
• ICS: 17.040.20 - Properties of surfaces
• ICS: 17.040.40 - Geometrical Product Specification (GPS)
• Technical Committee: ISO/TC 213 - Dimensional and geometrical product specifications and verification
• Drafting Committee: ISO/TC 213/WG 16 - Areal and profile surface texture
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 18-May-2026
• Completion Date: 18-May-2026

Relations

• Consolidates: FprEN ISO 25178-71 - Geometrical product specifications (GPS) - Surface texture: Areal - Part 71: Surface data file (SDF) file format (ISO/FDIS 25178‑71:2026)
• Effective Date: 12-Feb-2026
• Revises: ISO 25178-71:2017 - Geometrical product specifications (GPS) — Surface texture: Areal — Part 71: Software measurement standards
• Effective Date: 13-Jan-2024

Overview

ISO/FDIS 25178-71:2026 is an international standard developed by ISO (International Organization for Standardization) that specifies the Surface Data File (SDF) file format for surface texture measurements captured by the areal and profile methods. Falling under the broader framework of Geometrical Product Specifications (GPS), this standard defines two types of software measurement standards:

• Type S1 (softgauges or reference data): Computer-stored reference data for verifying instrument software.
• Type S2 (reference software): Certified software tools for validating measurement results.

The document provides detailed guidance on the SDF format’s ASCII and binary representations, facilitating calibration and software verification for measuring instruments. This ensures reliable and interoperable measurement data in applications involving surface topography.

Key Topics

• Areal and Profile Surface Texture Measurements: The standard supports areal (3D) and profile (2D) data, defined in orthogonal grids with equidistant sampling intervals, as specified in ISO 14406.
• SDF File Format Specification: Details the structure and essential records:
  • Header: Contains metadata (version, creation/modification dates, instrument ID, scale factors, and data types).
  • Data Area: Matrix-formatted encoded surface height values with support for marking non-measured or spurious data points.
  • Trailer: Holds historical information or additional metadata relevant to the measurement.
• Traceability and Calibration: Defines requirements for calibration certificates that accompany software measurement standards, emphasizing traceability, uncertainty declarations (per ISO/IEC Guide 98-3), and identification of used hardware and software.
• Data Integrity and Compatibility: Ensures SDF files are consistently formatted for interoperability across manufacturers and software systems, with explicit definitions for data types, encoding, and scalability.

Applications

The implementation of ISO/FDIS 25178-71:2026 and the SDF file format offers significant practical value in various industrial and research environments, such as:

• Instrument and Software Calibration: Enables manufacturers and users of surface texture measuring instruments to verify and calibrate measurement algorithms and software with certified reference data or reference software.
• Quality Control in Manufacturing: Ensures reliable surface measurement data, supporting consistent quality assurance in sectors like automotive, aerospace, and precision engineering.
• Research and Development: Facilitates the exchange of standardized surface texture measurements in academic and industrial R&D, promoting reproducibility.
• Regulatory Compliance: Assists companies in meeting international and customer-specific requirements for data traceability and measurement integrity.

By adopting this standard, organizations improve accuracy, consistency, and trust in surface texture measurement results, enhancing overall product quality.

Related Standards

ISO/FDIS 25178-71 is closely connected to the ISO GPS matrix and several fundamental standards, including:

• ISO 25178 series: Comprehensive standards for areal surface texture measurements and specifications.
• ISO 14638: Defines the ISO GPS (Geometrical Product Specifications) matrix model, situating this standard within the broader metrological framework.
• ISO 14406: Extraction procedures for measurement data.
• ISO/IEC Guide 98-3 (GUM): Guidelines for the expression of uncertainty in measurement.
• ISO 80000-2: Mathematical quantities and units used in the standard.
• IEEE 754: Floating-point arithmetic representation essentials for encoding numerical data.

Referencing these related standards ensures robust, traceable, and internationally recognized measurement and data management practices for areal and profile surface texture analysis.

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/TC 213
Geometrical product specifications
Secretariat: BSI
(GPS) — Surface texture: Areal —
Voting begins on:
2026-05-18
Part 71:
Surface data file (SDF) file format
Voting terminates on:
2026-07-13
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 213
Geometrical product specifications
Secretariat: BSI
(GPS) — Surface texture: Areal —
Voting begins on:
Part 71:
Surface data file (SDF) file format
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Types of software measurement standards . 4
4.1 General .4
4.2 Type S1, reference data .4
4.3 Type S2, reference software .4
5 File format for Type S1, reference data . 4
5.1 General .4
5.2 Record 1 — Header .5
5.2.1 General .5
5.2.2 Version number .5
5.2.3 Measurement instrument manufacturer's identifier .5
5.2.4 Original creation date and time .5
5.2.5 Last modification date and time.5
5.2.6 Number of columns in the data matrix, M .5
5.2.7 Number of rows in the data matrix, N .5
5.2.8 X-scale factor .5
5.2.9 Y-scale factor .6
5.2.10 Z-scale factor . .6
5.2.11 Z-resolution .6
5.2.12 Compression type .6
5.2.13 Data type .6
5.2.14 Checksum type . .6
5.2.15 Header description .6
5.3 Record 2 — Data area .7
5.3.1 General .7
5.3.2 Handling of non-measured or spurious points . .8
5.4 Record 3 — Trailer .8
6 Software measurement standard certificate . 9
Annex A (normative) ASCII and binary representation of the SDF format .10
Annex B (informative) Relationship to the GPS matrix model.12
Bibliography .13

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product
specifications and verification, in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 290, Dimensional and geometrical product specification and verification, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 25178-71:2017), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— the version number 2.0 has been added, which incorporates a number of new functionalities (see 5.2.2);
— in version number 2.0, the number of columns and the number of rows of the data matrix is represented
as a 4-byte unsigned integer instead of a 2-byte unsigned integer (see 5.2.6 and 5.2.7);
— in version number 2.0, two additional data types are available for data storage: a 1-byte signed integer
and a 4-byte floating point (see 5.2.13).
A list of all parts in the ISO 25178 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
This document is a geometrical product specification (GPS) standard and is to be regarded as a general GPS
standard (see ISO 14638). It influences the chain links F and G of the chains of standards on profile and areal
surface texture.
The ISO GPS matrix model given in ISO 14638 gives an overview of the ISO GPS system of which this document
is a part. The fundamental rules of ISO GPS given in ISO 8015 apply to this document and the default decision
rules given in ISO 14253-1 apply to the specifications made in accordance with this document, unless
otherwise indicated.
For more detailed information of the relation of this document to other standards and the GPS matrix model,
see Annex B.
This document is concerned with Type S1 software measurement standards (reference data), and Type S2
measurement standards (reference software). It also defines the surface data file (SDF) format for reference
data.
The SDF format is already used by the industry, in particular, by instrument manufacturers and academia.
The basic concept of the SDF format was originally developed for tactile measuring instruments as part of
[6]
the European Surfstand project and EUR 15178.

v
FINAL DRAFT International Standard ISO/FDIS 25178-71:2026(en)
Geometrical product specifications (GPS) — Surface texture:
Areal —
Part 71:
Surface data file (SDF) file format
1 Scope
This document specifies Type S1 software measurement standards, reference data, and Type S2 software
measurement standards, reference software, for verifying the software of measuring instruments. It also
specifies the surface data file (SDF) format of Type S1 software measurement standards for the calibration
of instruments for the measurement of surface texture by the profile and areal method as defined in the
profile and areal surface texture chain of standards, the chain links F and G.
The SDF format applies to profile and areal topography measurement data extracted with an orthogonal
grid (see ISO 14406:2010, 5.2) and equidistant sampling intervals, regardless of the measurement principle.
NOTE Throughout this document, the terms “reference data” and “reference software” are used as substitutes
for software measurement standards of Type S1 and Type S2, respectively. In practice, “reference data” is sometimes
referred to as “software gauge” or “softgauge”.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated terms
(VIM)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC Guide 99 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
software measurement standard
reference data or reference software intended to reproduce the value of a measurand with known
specification uncertainty, in order to verify the software used to calculate the value of a measurand
3.2
American Standard Code for Information Interchange
ASCII
7-bit character encoding which is congruent with UTF-8 encoding in the first 128 characters
Note 1 to entry: See ISO/IEC 10646.

3.3
uint8
1-byte (8-bit) representation of an unsigned integer
Note 1 to entry: The value range of "uint8" is from 0 to 255.
Note 2 to entry: In version number 1.0 of the SDF format, the term BYTE was used instead of uint8.
3.4
int8
1-byte (8-bit) representation of a signed integer
Note 1 to entry: The value range of “int8” is from −128 to 127.
3.5
uint16
2-byte representation of an unsigned integer
Note 1 to entry: The value range of “uint16” is from 0 to 65 535.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7]
“little endian” concept.
3.6
int16
2-byte representation of a signed integer
Note 1 to entry: The value range of “int16” is from −32 768 to 32 767.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7]
“little endian” concept.
3.7
uint32
4-byte representation of an unsigned integer
Note 1 to entry: The value range of “uint32” is from 0 to 4 294 967 295.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7]
“little endian” concept.
3.8
int32
4-byte representation of a signed integer
Note 1 to entry: The value range of “int32” is from −2 147 483 648 to 2 147 483 647.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7]
“little endian” concept.
3.9
binary32
4-byte single precision representation of a normalized floating point number according to IEEE 754
38 38
Note 1 to entry: The value range of “binary32” is from 3,402823466 10 to 3,402823466×10 .
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7]
“little endian” concept.
Note 3 to entry: Many programming languages support the 4-byte single precision representation in accordance with
IEEE 754. However, alternative terms are often used instead of “binary32”. For example, “float” in C and C++.

Note 4 to entry: The ASCII representation of a “binary32” number not equal to zero, see Figure 1, shall be a normalized,
signed floating point number in scientific notation with 7 significant digits and a signed two digit exponent in the
range from −38 to +38. If the “binary32” number is equal to zero, the format “0.000000e+00” shall be used.
Key
A sign for the fraction (“+ ” is optional)
B floating point number in the range 11, 0 with one digit before and 6 digits after the decimal point
 
C symbol for the exponent (“e” or “E”)
D sign for the exponent (“+ ” or “− “ is mandatory)
E integer number in the range 03, 8
 
Figure 1 — ASCII representation of “binary32” number
3.10
binary64
8-byte double precision representation of a normalized floating point number according to IEEE 754
Note 1 to entry: The value range of “binary64” is from 1,797693134862315710 to
1,797693134862315710 .
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7]
“little endian” concept.
Note 3 to entry: In version number 1.0 of the SDF format, the term “DOUBLE” was used instead of “binary64”.
Note 4 to entry: Many programming languages support the 8-byte double precision representation in accordance with
IEEE 754. However, alternative terms are often used instead of “binary64”. For example, “double” in C and C++.
Note 5 to entry: The ASCII representation of a “binary64” number not equal to zero, see Figure 2, shall be a normalized,
signed floating point number in scientific notation with 15 significant digits and a signed three digit exponent in the
range from −308 to +308. If the “binary64” number is equal to zero, the format “0.00000000000000e+000” shall be
used.
Key
A sign for the fraction (“+ ” is optional)
B floating point number in the range 11, 0 with one digit before and 14 digits after the decimal point
 
C symbol for the exponent (“e” or “E”)
D sign for the exponent (“+ ” or “− “ is mandatory)
E integer number in the range 0,308
 
Figure 2 — ASCII representation of “binary64” number
3.11
char[n]
array of dat
...

ISO /TC 213/WG 16
Secretariat: BSI
Date: 2026-01-2905-04
Geometrical product specifications (GPS) — Surface texture: Areal —
Part 71: Software measurement standards
Surface data file (SDF) file format
Spécification géométrique des produits (GPS) — État de surface: Surfacique — Partie 71: Étalons logiciels
FDIS stage
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Types of software measurement standards . 4
4.1 General . 4
4.2 Type S1, reference data . 4
4.3 Type S2, reference software . 5
5 File format for Type S1, reference data . 5
5.1 General . 5
5.2 Record 1 — Header . 5
5.3 Record 2 — Data area . 8
5.4 Record 3 — Trailer . 9
6 Software measurement standard certificate . 10
Annex A (normative) ASCII and binary representation of the SDF format . 12
Annex B (informative) Relationship to the GPS matrix model . 14
Bibliography . 16

© ISO 2026 – All rights reserved
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product
specifications and verification, in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 290, Dimensional and geometrical product specification and verification, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 25178--71:2017), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— — the version number 2.0 has been added, which incorporates a number of new functionalities (see
5.2.2);
Field Code Changed
— — in version number 2.0, the number of columns and the number of rows of the data matrix is
represented as a 4-byte unsigned integer instead of a 2-byte unsigned integer (see 5.2.6 and 5.2.7);
Field Code Changed
— — in version number 2.0, two additional data types are available for data storage: a 1-byte signed integer
and a 4-byte floating point (see 5.2.13).
A list of all parts in the ISO 25178 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
This document is a geometrical product specification (GPS) standard and is to be regarded as a general GPS
standard (see ISO 14638). It influences the chain links F and G of the chains of standards on profile and areal
surface texture.
The ISO GPS matrix model given in ISO 14638 gives an overview of the ISO GPS system of which this document
is a part. The fundamental rules of ISO GPS given in ISO 8015 apply to this document and the default decision
rules given in ISO 14253--1 apply to the specifications made in accordance with this document, unless
otherwise indicated.
For more detailed information of the relation of this document to other standards and the GPS matrix model,
see Annex BAnnex B.
This document is concerned with Type S1 software measurement standards (reference data), and Type S2
measurement standards (reference software). It also defines the surface data file (SDF) format for reference
data.
The SDF format is already used by the industry, in particular, by instrument manufacturers and academia. The
basic concept of the SDF format was originally developed for tactile measuring instruments as part of the
[6] [6]
European Surfstand project and EUR 15178. .
© ISO 2026 – All rights reserved
v
DRAFT International Standard ISO/FDIS 25178-71:2026(en)

Geometrical product specifications (GPS) — Surface texture: Areal —
Part 71: Software measurement standards
Surface data file (SDF) file format
1 Scope
This document specifies Type S1 software measurement standards, reference data, and Type S2 software
measurement standards, reference software, for verifying the software of measuring instruments. It also
specifies the surface data file (SDF) format of Type S1 software measurement standards for the calibration of
instruments for the measurement of surface texture by the profile and areal method as defined in the profile
and areal surface texture chain of standards, the chain links F and G.
The SDF format applies to profile and areal topography measurement data extracted with an orthogonal grid
(see ISO 14406:2010, 5.2) and equidistant sampling intervals, regardless of the measurement principle.
NOTE Throughout this document, the terms “reference data” and “reference software” are used as substitutes for
software measurement standards of Type S1 and Type S2, respectively. In practice, “reference data” is sometimes
referred to as “software gauge” or “softgauge”.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated terms
(VIM)
ISO/IEC 10646, Information technology — Universal coded character set (UCS)
ISO 80000-2, Quantities and units — Part 2: Mathematics
IEEE 754:2019, IEEE Standard for Floating-Point Arithmetic
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC Guide 99 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.1 3.1
software measurement standard
reference data or reference software intended to reproduce the value of a measurand with known
specification uncertainty, in order to verify the software used to calculate the value of a measurand
3.2
3.2
ASCII
American Standard Code for Information Interchange
ASCII
7-bit character encoding which is congruent with UTF-8 encoding in the first 128 characters
Note 1 to entry: See ISO/IEC 10646.
3.23.3 3.3
uint8
1-byte (8-bit) representation of an unsigned integer
Note 1 to entry: The value range of "uint8" is from 0 to 255.
Note 2 to entry: In version number 1.0 of the SDF format, the term BYTE was used instead of uint8.
3.33.4 3.4
int8
1-byte (8-bit) representation of a signed integer
Note 1 to entry: The value range of “int8” is from −128 to 127.
3.43.5 3.5
uint16
2-byte representation of an unsigned integer
Note 1 to entry: The value range of “uint16” is from 0 to 65 535.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7] [7]
“little endian” concept. .
3.53.6 3.6
int16
2-byte representation of a signed integer
Note 1 to entry: The value range of “int16” is from −32 768 to 32 767.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7] [7]
“little endian” concept. .
3.63.7 3.7
uint32
4-byte representation of an unsigned integer
Note 1 to entry: The value range of “uint32” is from 0 to 4 294 967 295.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7] [7]
“little endian” concept. .
ISO/DISFDIS 25178-71:2026(en)
3.73.8 3.8
int32
4-byte representation of a signed integer
Note 1 to entry: The value range of “int32” is from −2 147 483 648 to 2 147 483 647.
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7] [7]
“little endian” concept. .
3.83.9 3.9
binary32
4-byte single precision representation of a normalized floating point number according to IEEE 754
38 38 38 38
Note 1 to entry: The value range of “binary32” is from −3,402 823 466 × 10 10 to 3,402 823 466 × 10 10 .
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7] [7]
“little endian” concept. .
Note 3 to entry: Many programming languages support the 4-byte single precision representation in accordance with
IEEE 754. However, alternative terms are often used instead of “binary32”. For example, “float” in C and C++.
Note 4 to entry: The ASCII representation of a “binary32” number not equal to zero, see Figure 1Figure 1,, shall be a
normalized, signed floating point number in scientific notation with 7 significant digits and a signed two digit exponent
in the range from −38 to +38. If the “binary32” number is equal to zero, the format “0.000000e+00” shall be used.

Key
A sign for the fraction (“”(“+” is optional)
B floating point number in the range [1, 10] with one digit before and 6 digits after the decimal point
C symbol for the exponent (“e” or “E”)
D sign for the exponent (“”(“+” or “““−“ is mandatory)
E integer number in the range [0, 38][0,38]
Figure 1 — ASCII representation of “binary32” number
3.93.10 3.10
binary64
8-byte double precision representation of a normalized floating point number according to IEEE 754
308 308
Note 1 to entry: The value range of “binary64” is from −1,797 693 134 862 315 7 × 10 7976931348623157 × 10
308 308
to 1,797 693 134 862 315 7 × 10 7976931348623157 × 10 .
Note 2 to entry: The least significant byte shall be stored first in the lowest memory address, which is known as the
[7] [7]
“little endian” concept. .
Note 3 to entry: In version number 1.0 of the SDF format, the term “DOUBLE” was used instead of “binary64”.
Note 4 to entry: Many programming languages support the 8-byte double precision representation in accordance with
IEEE 754. However, alternative terms are often used instead of “binary64”. For example, “double” in C and C++.
© ISO 2026 – All rights reserved
Note 5 to entry: The ASCII representation of a “binary64” number not equal to zero, see Figure 2Figure 2,, shall be a
normalized, signed floating point number in scientific notation with 15 significant digits and a signed three digit exponent
in the range from −308 to +308. If the “binary64” number is equal to zero, the format “0.00000000000000e+000” shall
be used.
Key
A sign for the fraction (“”(“+” is optional)
B floating point number in the range [1, 10] with one digit before and 14 digits after the decimal point
C symbol for the exponent (“e” or “E”)
D sign for the exponent (“”(“+” or “““−“ is mandatory)
E integer number in the range [0, 308][0,308]
Figure 2 — ASCII representation of “binary64” number
3.103.11 3.11
char[n]
array of data type int8 for representing an ASCII character string
3.113.12 3.12
datetime
char[12] ASCII string representing the date and time in the format DDMMYYYYhhmm
where
DD is a two digit number of the day of month with leading zeros. Range [01, …, 31];
MM is a two digit number of the month with leading zeros. Range [01, …, 12], where 01 = January, …,
12 = December;
YYYY is a four digit number of the year;
hh is a two digit number with hour of day with leading zeros. Range [00, …, 23];
mm is a two digit number with minute of hour with leading zeros. Range [00, ., 59].
Note 1 to entry: For version number 2.0 of the SDF format, the time zone is coordinated universal time (UTC).
4 Types of software measurement standards
4.1 General
Software measurement standards are designed to verify the measuring instrument’s software (i.e. form
removal, filter algorithms, parameter calculation, etc.).
4.2 Type S1, reference data
Type S1 software measurement standards, reference data, are a computer data file that contains a digital
representation of a measured or mathematically generated surface in a suitable recording medium.
ISO/DISFDIS 25178-71:2026(en)
Reference data are used to test software by inputting them as data into the software under test or calibration
and comparing the results from the software under test with the certified results from the calibration
certificate.
NOTE The certified results for mathematically designed synthetic data can often be calculated directly without the
need for certification by Type S2 software measurement standards, reference software.
4.3 Type S2, reference software
Type S2 software measurement standards are reference software. Reference software consists of traceable
computer software against which software in a measuring instrument can be compared.
Reference softwares aresoftware is used to test software by inputting a common data set into the software
under test or calibration and the reference software and comparing the results from the software under test
with the certified results from the reference software. Reference software values shall be traceable.
NOTE 1 Traceable here means a traceable chain of comparisons, with uncertainty, back to a mathematically designed
synthetic data set whose results can be calculated directly.
NOTE 2 Type S2, reference software can also be used to certify Type S1, reference data.
5 File format for Type S1, reference data
5.1 General
The file extension of the SDF format is “.sdf”. The SDF format for the reference data is divided into three
records. This document defines the ASCII and binary representation of the SDF format. ASCII and binary
representation of the SDF format shall be according to Annex AAnnex A.
NOTE In case of a profile, the value of “Number of rows in the data matrix” is 1, and the value of “Y-scale factor” is
meaningless.
...

PROJET FINAL
Norme
internationale
ISO/TC 213
Spécification géométrique des
Secrétariat: BSI
produits (GPS) — État de surface :
Début de vote:
Surfacique —
2026-05-18
Partie 71:
Vote clos le:
2026-07-13
Format de fichier de surface (SDF)
Geometrical product specifications (GPS) — Surface texture:
Areal —
Part 71: Surface data file (SDF) file format
LES DESTINATAIRES DU PRÉSENT PROJET SONT
INVITÉS À PRÉSENTER, AVEC LEURS OBSERVATIONS,
NOTIFICATION DES DROITS DE PROPRIÉTÉ DONT ILS
AURAIENT ÉVENTUELLEMENT CONNAISSANCE ET À
FOURNIR UNE DOCUMENTATION EXPLICATIVE.
OUTRE LE FAIT D’ÊTRE EXAMINÉS POUR
ÉTABLIR S’ILS SONT ACCEPTABLES À DES FINS
INDUSTRIELLES, TECHNOLOGIQUES ET COM-MERCIALES,
AINSI QUE DU POINT DE VUE DES UTILISATEURS, LES
PROJETS DE NORMES
TRAITEMENT PARALLÈLE ISO/CEN
INTERNATIONALES DOIVENT PARFOIS ÊTRE CONSIDÉRÉS
DU POINT DE VUE DE LEUR POSSI BILITÉ DE DEVENIR DES
NORMES POUVANT
SERVIR DE RÉFÉRENCE DANS LA RÉGLEMENTATION
NATIONALE.
Numéro de référence
PROJET FINAL
Norme
internationale
ISO/TC 213
Spécification géométrique des
Secrétariat: BSI
produits (GPS) — État de surface :
Début de vote:
Surfacique —
2026-05-18
Partie 71:
Vote clos le:
2026-07-13
Format de fichier de surface (SDF)
Geometrical product specifications (GPS) — Surface texture:
Areal —
Part 71: Surface data file (SDF) file format
LES DESTINATAIRES DU PRÉSENT PROJET SONT
INVITÉS À PRÉSENTER, AVEC LEURS OBSERVATIONS,
NOTIFICATION DES DROITS DE PROPRIÉTÉ DONT ILS
AURAIENT ÉVENTUELLEMENT CONNAISSANCE ET À
FOURNIR UNE DOCUMENTATION EXPLICATIVE.
DOCUMENT PROTÉGÉ PAR COPYRIGHT
OUTRE LE FAIT D’ÊTRE EXAMINÉS POUR
ÉTABLIR S’ILS SONT ACCEPTABLES À DES FINS
© ISO 2026 INDUSTRIELLES, TECHNOLOGIQUES ET COM-MERCIALES,
AINSI QUE DU POINT DE VUE DES UTILISATEURS, LES
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
PROJETS DE NORMES
TRAITEMENT PARALLÈLE ISO/CEN
INTERNATIONALES DOIVENT PARFOIS ÊTRE CONSIDÉRÉS
publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
DU POINT DE VUE DE LEUR POSSI BILITÉ DE DEVENIR DES
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
NORMES POUVANT
être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
SERVIR DE RÉFÉRENCE DANS LA RÉGLEMENTATION
NATIONALE.
ISO copyright office
Case postale 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Genève
Tél.: [phone]
E-mail: [e-mail]
Web: www.iso.org
Publié en Suisse Numéro de référence
ii
Sommaire Page
Avant-propos .iv
Introduction .v
1 Domaine d'application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Types d'étalons logiciels .4
4.1 Généralités .4
4.2 Données de référence, Type S1 . .4
4.3 Logiciel de référence, Type S2 .5
5 Format de fichier pour les données de référence, Type S1 . 5
5.1 Généralités .5
5.2 Enregistrement 1 — En-tête .5
5.2.1 Généralités .5
5.2.2 Numéro de version . .5
5.2.3 Identifiant du fabricant de l'instrument de mesure .5
5.2.4 Date et heure de création initiale .5
5.2.5 Date et heure de dernière modification .6
5.2.6 Nombre de colonnes dans la matrice de données, M .6
5.2.7 Nombre de lignes dans la matrice de données, N .6
5.2.8 Facteur d’échelle de l’axe X .6
5.2.9 Facteur d’échelle de l’axe Y .6
5.2.10 Facteur d’échelle de l’axe Z .6
5.2.11 Résolution d'axe Z .6
5.2.12 Type de compression .6
5.2.13 Type de données .6
5.2.14 Type de somme pour la vérification .7
5.2.15 Description des en-têtes .7
5.3 Enregistrement 2 — Zone de données .8
5.3.1 Généralités .8
5.3.2 Traitement des points non mesurés ou aberrants .9
5.4 Enregistrement 3 — Section terminale .9
5.5 Certificat de l'étalon logiciel .10
Annexe A (normative) Représentation ASCII et binaire du format SDF .11
Annexe B (informative) Relation avec le modèle de matrice GPS .13
Bibliographie . 14

iii
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes nationaux
de normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est en général
confiée aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude a le droit de faire
partie du comité technique créé à cet effet. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec l'ISO participent également aux travaux. L'ISO collabore étroitement avec
la Commission électrotechnique internationale (IEC) en ce qui concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents
critères d'approbation requis pour les différents types de documents ISO. Le présent document a
été rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir
www.iso.org/directives).
L’ISO attire l’attention sur le fait que la mise en application du présent document peut entraîner l’utilisation
d’un ou de plusieurs brevets. L’ISO ne prend pas position quant à la preuve, à la validité et à l’applicabilité de
tout droit de propriété revendiqué à cet égard. À la date de publication du présent document, l’ISO n'avait pas
reçu notification qu’un ou plusieurs brevets pouvaient être nécessaires à sa mise en application. Toutefois,
il y a lieu d’avertir les responsables de la mise en application du présent document que des informations
plus récentes sont susceptibles de figurer dans la base de données de brevets, disponible à l'adresse
www.iso.org/brevets. L’ISO ne saurait être tenue pour responsable de ne pas avoir identifié tout ou partie de
tels droits de propriété.
Les appellations commerciales éventuellement mentionnées dans le présent document sont données pour
information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion de
l'ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles techniques au
commerce (OTC), voir www.iso.org/avant-propos.
Le présent document a été élaboré par le comité technique ISO/TC 213, Spécifications et vérification
dimensionnelles et géométriques des produits, en collaboration avec le comité technique CEN/TC 290,
Spécification dimensionnelle et géométrique des produits, et vérification correspondante, du Comité européen
de normalisation (CEN) conformément à l’Accord de coopération technique entre l’ISO et le CEN (Accord de
Vienne).
Cette troisième édition annule et remplace la deuxième édition (ISO 25178-71:2017), qui a fait l'objet d'une
révision technique.
Les principales modifications par rapport à l'édition précédente sont les suivantes:
— le numéro de version 2.0 a été ajoutée qui intègre un certain nombre de nouvelles fonctionnalités (voir
5.2.2);
— dans le numéro de version 2.0, le nombre de colonnes et le nombre de lignes de la matrice de données
est représenté par un entier non signé de 4 octets au lieu d’un entier non signé de 2 octets (voir 5.2.6 et
5.2.7);
— dans le numéro de version 2.0, deux types de données supplémentaires sont disponibles pour le stockage
des données: un entier signé d’un octet et une virgule flottante de quatre octets (voir 5.2.13).
Une liste de toutes les parties de la série ISO 25178 se trouve sur le site web de l'ISO.
Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent
document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes se
trouve à l’adresse www.iso.org/members.html.

iv
Introduction
Le présent document est une norme de spécification géométrique des produits (GPS) et est à considérer
comme une norme GPS générale (voir l'ISO 14638). Il influence les maillons F et G des chaînes de normes sur
l’état de surface du profil et surfacique.
Le modèle de matrice ISO GPS de l’ISO 14638 donne une vue d’ensemble du système ISO GPS, dont le présent
document fait partie. Les principes fondamentaux du système ISO GPS donnés dans l’ISO 8015 s’appliquent
au présent document et les règles de décision par défaut données dans l’ISO 14253-1 s’appliquent aux
spécifications faites conformément au présent document, sauf indication contraire.
Pour de plus amples informations sur la relation du présent document avec les autres normes et le modèle de
matrice GPS, voir l’Annexe B.
Le présent document traite des étalons logiciels (données de référence) de Type S1 et les étalons de référence
(logiciel de référence) de Type S2. Il définit également le format (SDF) de fichier de données de surface pour
les données de référence.
Le format SDF est déjà utilisé par l'industrie, en particulier par les fabricants d'instruments et le monde
universitaire. Le concept de base du format SDF a été développé à l’origine pour les instruments de mesure
[6]
tactiles dans le cadre du projet européen Surfstand et de l’EUR 15178 .

v
PROJET FINAL Norme internationale ISO/FDIS 25178-71:2026(fr)
Spécification géométrique des produits (GPS) — État de
surface : Surfacique —
Partie 71:
Format de fichier de surface (SDF)
1 Domaine d'application
Le présent document spécifie les étalons logiciels, données de référence, de Type S1 et les étalons logiciels,
logiciel de référence, de Type S2 qui permettent de vérifier les logiciels des instruments de mesure. Il spécifie
également le format (SDF) de fichier de données de surface des étalons logiciels de Type S1 pour l’étalonnage
des instruments destinés au mesurage de l’état de surface par la méthode du profil et la méthode surfacique
telle que définie dans les maillons F et G de la chaîne de normes sur l'état de surface du profil et surfacique.
Le format SDF s'applique aux données de mesure topographique de profil et surfacique extraites avec une
grille orthogonale (voir l’ISO 14406:2010, 5.2) et des intervalles d’échantillonnage équidistants, quel que
soit le principe de mesure.
NOTE Dans le présent document, les termes «données de référence» et «logiciel de référence» sont utilisés somme
substitut pour étalons logiciel de Type S1 et de Type S2, respectivement. En pratique, «données de référence» est
parfois référencé comme «calibre logiciel» ou «calibre virtuel».
2 Références normatives
Les documents suivants sont cités dans le texte de sorte qu’ils constituent, pour tout ou partie de leur
contenu, des exigences du présent document. Pour les références datées, seule l’édition citée s'applique. Pour
les références non datées, la dernière édition du document de référence s'applique (y compris les éventuels
amendements).
Guide ISO/IEC 99, Vocabulaire international de métrologie — Concepts fondamentaux et généraux et termes
associés (VIM)
3 Termes et définitions
Pour les besoins du présent document, les termes et les définitions de l'ISO/IEC Guide 99, ainsi que les
suivants s’appliquent.
L'ISO et l'IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en normalisation,
consultables aux adresses suivantes:
— ISO Online browsing platform: disponible à l'adresse https:// www .iso .org/ obp
— IEC Electropedia: disponible à l'adresse https:// www .electropedia .org/
3.1
étalon logiciel
donnée de référence ou logiciel de référence destiné(e) à reproduire la valeur d'un mesurande avec une
incertitude de spécification connue, afin de vérifier le logiciel utilisé pour calculer la valeur d'un mesurande

3.2
American Standard Code for Information Interchange
ASCII
encodage de caractères 7-bits qui est conforme à l’encodage UTF-8 dans les 128 premiers caractères
Note 1 à l'article: Voir l’ISO/IEC 10646.
3.3
uint8
représentation d'un entier non signé codée sur 1 octet (8 bits)
Note 1 à l'article: La plage de valeurs de «uint8» est comprise entre 0 et 255.
Note 2 à l'article: Dans le numéro de version 1.0 du format SDF, le terme BYTE a été utilisé à la place de uint8.
3.4
int8
représentation d’un entier signé codée sur 1 octet (8 bits)
Note 1 à l'article: La plage de valeurs de «int8» est comprise entre −128 et 127.
3.5
uint16
représentation d'un entier non signé codée sur 2 octets
Note 1 à l'article: La plage de valeurs de «uint16» est comprise entre 0 et 65 535.
Note 2 à l'article: L’octet de poids faible doit être stocké d’abord dans l’adresse mémoire la plus basse, ce qui est connu
[7]
en tant que concept «little endian».
3.6
int16
représentation d’un entier signé codée sur 2 octets
Note 1 à l'article: La plage de valeurs de «int16» est comprise entre −32 768 et 32 767.
Note 2 à l'article: L’octet de poids faible doit être stocké d’abord dans l’adresse mémoire la plus basse, ce qui est connu
[7]
en tant que concept «little endian».
3.7
uint32
représentation d'un entier non signé codée sur 4 octets
Note 1 à l'article: La plage de valeurs de «uint32» est comprise entre 0 et 4 294 967 295.
Note 2 à l'article: L’octet de poids faible doit être stocké d’abord dans l’adresse mémoire la plus basse, ce qui est connu
[7]
en tant que concept «little endian».
3.8
int32
représentation d’un entier signé codée sur 4 octets
Note 1 à l'article: La plage de valeurs de «int32» est comprise entre −2 147 483 648 et 2 147 483 647.
Note 2 à l'article: L’octet de poids faible doit être stocké d’abord dans l’adresse mémoire la plus basse, ce qui est connu
[7]
en tant que concept «little endian».

3.9
binary32
représentation à précision unique codée sur 4 octets d’un nombre à virgule flottante normalisé
conformément à l’IEEE 754
38 38
Note 1 à l'article: La plage de valeurs de «binary32» est comprise entre 3,402823466 10 et3,402823466×10
.
Note 2 à l'article: L’octet de poids faible doit être stocké d’abord dans l’adresse mémoire la plus basse, ce qui est connu
[7]
en tant que concept «little endian».
Note 3 à l'article: De nombreux langages de programmation prennent en charge la représentation à précision unique
codée sur 4 octets conformément à l’IEEE 754. Cependant, des termes de remplacement sont souvent utilisés à la place
de «binary32». Par exemple, «float» dans C et C++.
Note 4 à l'article: La représentation ASCII d’un nombre «binary32» non égal à zéro, voir Figure 1, doit être un nombre
normalisé, en virgule flottante signé en notation scientifique avec 7 chiffres significatifs et un exposant signé à deux
chiffres dans la plage de −38 à +38. Si le nombre «binary32» est égal à zéro, le format «0.000000e+00» doit être utilisé.
Légende
A signe pour la fraction (“+ ” est facultatif)
B nombre à virgule flottante dans la plage 11, 0 avec un chiffre avant et 6 chiffres après la virgule
 
C symbole pour l’exposant (“e” ou “E”)
D signe pour l’exposant (“+ ” ou “− ” est obligatoire)
E nombre entier dans la plage 03, 8
 
Figure 1 — Représentation ASCII du nombre «binary32»
3.10
binary64
représentation à double précision codée sur 8 octets d’un nombre à virgule flottante normalisé conformément
à l’IEEE 754
Note 1 à l'article: La plage de valeurs de «binary64» est comprise entre 1,797693134862315710 et
1,797693134862315710 .
Note 2 à l'article: L’octet de poids faible doit être stocké d’abord dans l’adresse mémoire la plus basse, ce qui est connu
[7]
en tant que concept «little endian».
Note 3 à l'article: Dans le numéro de version 1.0 du format SDF, le terme «DOUBLE» a été utilisé à la place de «binary64».
Note 4 à l'article: De nombreux langages de programmation prennent en charge la représentation à double précision
codée sur 8 octets, conformément à l’IEEE 754. Cependant, des termes de remplacement sont souvent utilisés à la place
de «binary64». Par exemple, «double» dans C et C++.
Note 5 à l'article: La représentation ASCII d’un nombre «binary64» non égal à zéro, voir Figure 2, doit être un nombre
normalisé, en virgule flottante signé en notation scientifique avec 15 chiffres significatifs et un exposant signé à trois
chiffres dans la plage de −308 à +308. Si le nombre «binary64» est égal à zéro, le format «0.00000000000000e+000»
doit être utilisé.
Légende
A signe pour la fraction (“+ ” est facultatif)
B nombre à virgule flottante dans la plage 11, 0 avec un chiffre avant et 14 chiffres après la virgule
 
 
C symbole pour l’exposant (“e” ou “E”)
D signe pour l’exposant (“+ ” ou “− ” est obligatoire)
E nombre entier dans la plage 0,308
 
Figure 2 — Représentation ASCII du nombre «binary64»
3.11
char[n]
tableau de type de données int8 pour représenter une chaîne de caractères ASCII
3.12
datetime
chaîne ASCII char[12 ] représentant la date et l’heure au format JJMMAAAAhhmm
où
JJ est un nombre à deux chiffres du jour du mois avec des zéros à gauche. Plage [01, …, 31];
MM est un nombre à deux chiffres du mois avec des zéros à gauche. Plage [01, …, 12], où 01 = Janvier
...