MAT-File Format - SERC

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1 MAT-File FormatMAT-File Header FormatLevel 5 MAT-files begin with a 128-byte header made up of a 124 byte text fieldand two, 16-bit flag fields.This section covers the following topics:• “Header Text Field” on page 1-6• “Header Subsystem Data Offset Field” on page 1-7• “Header Flag Fields” on page 1-7Header Text FieldThe first 116 bytes of the header can contain text data in human-readable form.This text typically provides information that describes how the MAT-file wascreated. For example, MAT-files created by MATLAB include the followinginformation in their headers:• Level of the MAT-file (value equals 1 for Level 5)• Platform on which the file was created• Date and time the file was createdYou can view the text in a MAT-file header using the cat command on UNIXsystems, or the type command on a PC. The output displays the text in thispart of the header. (The display of the header is followed by unreadablecharacters representing the binary data in the file.)cat my_matfile.matMATLAB 5.0 MAT-file, Platform: SOL2, Created on: Thu Nov 1310:10:27 1997Note When creating a MAT-file, you must write data in the first four bytes ofthis header. MATLAB uses these bytes to determine if a MAT-file uses a Level5 format or a Level 4 format. If any of these bytes contain a zero, MATLABwill incorrectly assume the file is a Level 4 MAT-file.1-6
Level 5 MAT-File FormatHeader Subsystem Data Offset FieldBytes 117 through 124 of the header contain an offset to subsystem-specificdata in the MAT-file. All zeros or all spaces in this field indicate that there isno subsystem-specific data stored in the file.Header Flag FieldsThe last four bytes in the header are divided into two, 16-bit flag fields (int16).FieldValueVersion When creating a MAT-file, set this field to 0x0100.EndianIndicatorContains the two characters, M and I, written to theMAT-file in this order, as a 16-bit value. If, when readfrom the MAT-file as a 16-bit value, the characters appearin reversed order (IM rather than MI), it indicates that theprogram reading the MAT-file must performbyte-swapping to interpret the data in the MAT-filecorrectly.Note Programs that create MAT-files always write data in their nativemachine format. Programs that read MAT-files are responsible forbyte-swapping.1-7
Page 1 and 2: MATLAB®The Language of Technical C
Page 3: Revision History:June 1999 Online o
Page 6 and 7: 1 MAT-File FormatIntroductionThis d
Page 8 and 9: 1 MAT-File FormatLevel 5 MAT-File F
Page 12 and 13: 1 MAT-File FormatData Element Forma
Page 14 and 15: 1 MAT-File FormatFor character data
Page 17 and 18: Level 5 MAT-File FormatEach variabl
Page 19 and 20: Level 5 MATLAB Array Data Element F
Page 29: Level 5 MATLAB Array Data Element F
Page 32 and 33: 1 MAT-File Formatsee “Numeric Arr
Page 34 and 35: 1 MAT-File FormatDimensions Array S
Page 36 and 37: 1 MAT-File FormatFigure 1-14: Examp
Page 38 and 39: 1 MAT-File FormatClass. This field
Page 40 and 41: 1 MAT-File FormatLevel 4 MAT-File F
Page 42 and 43: 1 MAT-File FormatTable 1-8: Level 4
Page 44 and 45: 1 MAT-File FormatAgain, we strongly
Page 46 and 47: IndexHheaderdefined 1-4flag fields
Page 48: IndexIndex-4

MAT-File Format - SERC

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