.TAP File Format

Introduction

A KC-TAP file holds one program (or several, one after another) as the tape of the VEB Mikroelektronik home computers KC 85/1, KC 87, Z 9001 and KC 85/2 to 5 stores it. The format comes from the emulator tools of Arne Fitzenreiter (the signature reads “KC-TAPE by AF”) and is read by several KC emulators. The extension .tap is shared with unrelated tape files; the explorer tells this one by its 16-byte signature, which begins with the byte C3.

Structure

A signature of 16 bytes, then blocks of 129 bytes: a lead byte and 128 data bytes. The first block is the header (128 bytes as in a KCC file: name, number of addresses, load, end and start address); the next blocks carry the program, from the load address to the end address, 128 bytes to a block. See Signature, header and data blocks.

In the explorer

Drop a KC-TAP file on the explorer to see:

• the tree: every tape file with its signature, the header block with its fields (name, number of addresses, load, end and start address), the data blocks;
• a table of the files (name, addresses, bytes, blocks), each file to open as bytes (the program without the lead bytes);
• the program disassembled as Z80 code at its load address with our decoder (the KC 85 and Z 9001 CPU is the U880, a Z80 clone), starting at the start address when the header gives one;
• the problems found: a cut file, an end address not above the load address, more than 3 addresses, a data length that the blocks do not hold, bytes that are not a following signature.

Not described

Known, not yet covered

• Viewer: the file type of the program (the loader’s kind: machine code, BASIC, the “COM” name extension) is not interpreted, the KC BASIC token table is not used, and no KC 85 or Z 9001 system labels are shown in the disassembly; the lead bytes are shown but not checked.
• Reference: the KCC file format (the same header without the signature and lead bytes) has no page of its own.

Unknown

• Reference: the meaning of the five bytes after the 8 + 3 name in the 16-byte name field: zero in several real files, other values in others (see the layout page).
• Reference: no specification by the format’s author was found; the layout rests on the chips source and the wiki page.

Also used for

• Acorn Atom tape file – The programs of an Acorn Atom cassette: ATM files, each a 22-byte header and its data.
• Amstrad CPC tape file – The blocks an Amstrad CPC writes to cassette: header and data blocks, each with a length and a flag byte.
• Commodore 64 tape image – The length of every pulse on a C64, VIC-20, C16 or PET tape, after the text C64-TAPE-RAW.
• Oric tape image – Oric-1 and Atmos tapes: a $16 leader, sync byte $24, a 9-byte header, name and data.
• SIMH tape image – The magnetic tape of the SIMH simulators: records framed by a 32-bit length at both ends, and tape marks.
• ZX Spectrum tape image – Spectrum tape blocks as plain bytes, each after a 2-byte length.

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