Question 1

What does this tool do?

Accepted Answer

It parses Psion TCR files by reading the 8-byte PCF magic header, loading the 256-entry code dictionary (variable-length codes 1-2 bytes each), decoding the compressed text stream bit-by-bit, splitting the resulting text into chapters by heading detection, and generating a valid EPUB 3 archive with both NCX (EPUB 2) and NAV (EPUB 3) tables of contents. The result opens in Apple Books, Calibre, Kobo, Nook, and most e-readers.

Question 2

What is the TCR format?

Accepted Answer

TCR is a simple text compression format used by Psion Series 3/5 PDAs and the EPOC operating system. It's essentially a Huffman-style code dictionary compressor: the file starts with a 'PCF' magic, then a 256-entry dictionary where each entry is a variable-length byte string (1-2 bytes), then the compressed text stream. Each byte in the compressed stream indexes into the dictionary to produce 1-2 output bytes.

Question 3

Is TCR the same as compressed text?

Accepted Answer

Yes — TCR is essentially a static dictionary compressor. The dictionary is per-file (stored at the start), so each TCR file is self-describing. Compression ratio is typically 40-50% for English text. We decompress fully client-side and report the compression ratio in the stats.

Question 4

What extra features does this tool have compared to others?

Accepted Answer

10 extras: (1) Drag-drop input. (2) Custom title and author metadata. (3) Stats — words, characters, compression ratio. (4) Live preview of the first chapter's XHTML. (5) Custom CSS injection into the EPUB stylesheet. (6) Configurable base font size (10–36pt). (7) Conversion history in localStorage (last 10). (8) Shareable URL with conversion options. (9) Chapter detection by heading. (10) Both NCX (EPUB 2) and NAV (EPUB 3) tables of contents for maximum reader compatibility.

Question 5

Is my TCR file uploaded anywhere?

Accepted Answer

No. All TCR parsing, dictionary decompression, EPUB XML generation, and ZIP packaging happens in your browser. File contents never leave your device.

Question 6

What is the compression ratio I see in stats?

Accepted Answer

The compression ratio is calculated as compressedBytes / decompressedBytes. For example, a ratio of 0.55 means the compressed TCR file is 55% the size of the decompressed text. A ratio near 1.0 means little compression was achieved (e.g., the file was already random or had a poor dictionary).

TCR to EPUB Converter

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