CTF File

What are CTF files and how to open them

Are you having problems opening a CTF file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CTF files.

What is a CTF file?

CTF files have multiple uses, and Casio Calculator Text Format Program is one of them. Read more about the other uses further down the page.

Casio Calculator Text Format Program

Calculator Text Format Program files hold programs written for vintage Casio scientific or graphing calculators. They are plaintext files used to represent calculator programs in a human-editable way so that utilities like the free software CaS or Casetta can exchange, display, or archive them. The format was invented by Tom Wheeley in 1997 as part of community efforts to document Casio formats.

Such files are produced by converting a calculator's built-in program (often in Casio BASIC) into a text representation, with special commands and symbols rendered as named keywords or custom tokens. They can contain multiple program records in one file; each record begins with @@Program and includes the program name, the program source as text, and associated metadata. Casetta and CaS can load these text files, show their contents, and when transferred back to a supported calculator or via an interface, convert them back into executable calculator programs.

Data begins with the ASCII signature @@Program (bytes 0x40402050726F6772616D2022) at file offset zero.

How to open CTF files

Important: Different programs may use files with the CTF file extension for different purposes, so unless you are sure which format your CTF file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested ten different CTF openers which you will find listed below.

Last updated: September 19, 2026

All known file formats using extension .CTF

While Casio Calculator Text Format Program is a popular type of CTF-file, we know of 2 different uses of the .CTF file extension. Different software may use files with the same extension for different types of data.

WhereIsIt? Catalog File

WhereIsIt Catalog File stores all the information that the WhereIsIt media cataloging program keeps about a media collection so that the catalog can be browsed, searched, shared, and updated without re-scanning physical media.

This format is produced and used by the Windows software WhereIsIt, created by Robert Galle. It holds records for items such as CDs, DVDs, disk images, files and folders, along with metadata like names, file sizes, dates, thumbnails, custom descriptions, flags, categories and alias names. The catalog is a single file, not a complex multi-file database.

The catalog file can include data from multiple disks or drives, and supports storing data even when the original media is not present on the computer. It can scan inside compressed archive files (if enabled), generate thumbnails, allow custom metadata up to several kilobytes per item, and be exported to formats like ASCII text, HTML, Excel, or RTF reports. WhereIsIt optimizes the catalog's internal structure for fast searching and compact size, so catalogs with tens of thousands of files use relatively little space.

The file begins with a header identifying it as version 3.00 of the catalog format, starting with the ASCII string "Catalog3.00" at the very beginning, followed by zero bytes at several specific offsets in the header.

Various apps that use files with this extension

These apps are known to open certain types of CTF files. Remember, different programs may use CTF files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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