Also Known As: North American Presentation Layer Protocol Syntax

Type Graphics Protocol/Metafile
Colors NA
Compression None
Maximum Image Size NA
Multiple Images Per File Yes
Numerical Format ASCII
Originator ISO/ANSI/CSA
Platform All
Supporting Applications Videotex services, Prodigy
See Also None

Transfer of graphics information to devices such as modems and terminals.

Although not strictly a file format, NAPLPS is likely to become the basis of one, because it is in wide use in a rapidly growing segment of the computer communications industry.

Vendor specifications are available for this format.

Sample images are available for this format.

NAPLPS (North American Presentation Layer Protocol Syntax) was designed as an information transfer protocol rather than as a file format. However, because NAPLPS data is occasionally written to disk and saved in file form, it is only a matter of time before an actual format stabilizes. For this reason, we are including summary information about NAPLPS in this book.

For Further Information

NAPLPS is used by a number of Videotex services, is supported by special NAPLPS terminals, and is used by Prodigy, a well-known commercial online service. NAPLPS was designed to extend ASCII to provide efficient transmission of text and picture information. It was specifically designed to provide usable information transfer rates even at 2400 baud. Data is sent as a stream of 7-bit or 8-bit ASCII characters to provide maximum compatibility with all ASCII-based operating platforms, network hardware, and network software.

NAPLPS defines line, box, circle, arc, polyline, polygon, spline, bitmaps, and fonts, both in palette and 24-bit color. The coordinate model is right-handed Cartesian, meaning that X and Y coordinates increase toward the upper-right of the screen.

A NAPLPS code sequence begins with the characters ESC 25 41 and ends with the sequence ESC 25 40. NAPLPS code sequences are designed with an eye toward avoiding standard terminal escape sequences such as those provided by VT100 and ANSI. NAPLPS files are basically segments of the NAPLPS data stream redirected to a file. Properly formatted, NAPLPS data files are not unlike uuencoded binary files. Proponents of NAPLPS claim great efficiencies from the encoding scheme. Much of the burden for image reconstruction falls on the rendering application, so a combination of low-bandwidth transmission channels and high-performance workstations would work well with NAPLPS. Unfortunately, the trend in recent years has been for data to be sent in bitmap format across channels of increasing bandwidth, so it's not clear what the future of NAPLPS will be.

A number of terminal programs currently support NAPLPS on both the PC and the Macintosh platforms.

For Further Information

For further information about NAPLPS, see the excellent article by Michael Dillon included on the CD-ROM. This article provides an overview and some detailed information about NAPLPS. You can also contact Mr. Dillon at:

Michael Dillon
CompuServe: 71532,137

Also check out the TurBoard NAPLPS BBS homepage at:

NAPLPS is formally defined in standards documents available for purchase from the International Standards Organization (ISO), the American National Standards Institute (ANSI), and the Canadian Standards Association (CSA). Note that information contained in the CSA supplement (see below) is not included in the ANSI version of the document.

International Standards Organization (ISO)
1 rue de Varembe
Case Postal 56
CH-1211 Geneva 20 Switzerland
Voice: +41 22 749 01 11
FAX: +41 22 733 34 30

Ask ISO for the NAPLPS specification.

American National Standards Institute (ANSI)
Attn: Sales Department
1430 Broadway
New York NY 10018
Voice: 212-642-4900

Ask ANSI for document number X3.110-1983.

Canadian Standards Association (CSA)
Attn: Sales Group
178 Rexdale Blvd.
Rexdale, Ontario M9W 1R3
Voice: 416-747-4044

Ask CSA for document number T500-1983 and supplement number 1-1991.

Further information about the NAPLPS format can be found in the February, March, April, and May 1983 issues of Byte magazine.

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