C File

What are C files and how to open them

Are you having problems opening a C 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 C files.

What is a C file?

C files have multiple uses, and C Source Code is one of them. Read more about the other uses further down the page.

C Source Code File

Files that contain the .c file extension normally contain source code that has been written for C or C++ programs. The C file may contain the source code for an entire program or a single source file that is to be referenced within a specific programming project.

The C programming language was developed as a general-purpose computer language by Dennis Ritchie. It was initially intended to be used for Unix operating systems. In 1983 the C++ programming language was developed by Bjarne Stroustrup as an enhancement to the original C language. Both the C and C+++ languages are two of the most widely-used programming languages in use today.

How to open C files

We have identified eight C openers that are compatible with this specific type of C file.

Programs that open C Source Code files

Last updated: August 25, 2026

All known file formats using extension .C

While C Source Code File is a popular type of C-file, we know of 3 different uses of the .C file extension. Different software may use files with the same extension for different types of data.

Compact Compressed Data File

Compact Compressed Data Files store output produced by the Unix compact utility, which uses adaptive Huffman coding to compress ordinary files. The format enables file contents to be reduced in size by encoding each byte according to a prefix-code that evolves as the file is processed. The utility produces a compressed version of a file and discards the original, naming the new file by appending ".C" to the original name. The compression method works in a streaming, "on-line" manner so that the decoder does not need a separate static codebook - it synchronizes with the encoder's evolving model as data is read. The typical compression reduction depends on file type (for example: about 38 % reduction for plain text, 36 % for C source, and 19 % for binary).

Restoration of the original data is done using the uncompact utility, which reads the compressed .C file, reconstructs the adaptive Huffman model incrementally, and outputs the original file. The compact‐format file includes two special bytes at its beginning which mark that it is already compacted; this prevents compact from compressing a file twice.

Signature details: the first two bytes (at offset 0) encode a fixed marker that identifies the file as compacted data and prevents recompaction. TRiD recognizes this format by the byte pattern 0xFF1F at offset 0.

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

PADS Parts Library Schematic Decals

PADS Parts Library Schematic Decals files store the graphical definitions of schematic symbols (called CAE decals) for PADS Logic ("Logic/CAE") library items. They hold the symbol shapes, terminal placement, drawing primitives, and associated visual attribute data - the parts that define how each component appears on a schematic.

These files are produced by the Library Manager inside PADS Logic when exporting "CAE Decals" to ASCII format. They are used alongside a parts file (which holds the electrical attributes, pins, part number, footprint pointers, etc.) to form a complete PADS schematic symbol library. Reading programs like Altium Designer or KiCad import the CAE decal file together with the parts attribute file in order to reconstruct the full schematic symbol.

Internally the file is a text-based ASCII document using defined keywords and sections. It begins with a header identifying it as a CAE Decal (Logic) export from PADS, version information, and units. It includes schematic decal definitions, text definitions, terminal (pin) definitions, and drawing primitives (lines, arcs) in specified coordinate units (mils) etc.

Various apps that use files with this extension

These apps are known to open certain types of C files. Remember, different programs may use C 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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