Header Record

The file begins with a 128 byte header record that describes the location and size of the chromatogram data in the file. Nothing is implied about the order in which the components (samples, sequence and comments) appear. The version field is a 4 byte character array representing the version and revision of the SCF format. The current value of this field is "3.00".

/*
 * Basic type definitions
 */
typedef unsigned int   uint_4;
typedef signed   int    int_4;
typedef unsigned short uint_2;
typedef signed   short  int_2;
typedef unsigned char  uint_1;
typedef signed   char   int_1;

/*
 * Type definition for the Header structure
 */
#define SCF_MAGIC (((((uint_4)'.'<<8)+(uint_4)'s'<<8) \
                     +(uint_4)'c'<<8)+(uint_4)'f')

typedef struct {
    uint_4 magic_number;
    uint_4 samples;          /* Number of elements in Samples matrix */
    uint_4 samples_offset;   /* Byte offset from start of file */
    uint_4 bases;            /* Number of bases in Bases matrix */
    uint_4 bases_left_clip;  /* OBSOLETE: No. bases in left clip (vector) */
    uint_4 bases_right_clip; /* OBSOLETE: No. bases in right clip (qual) */
    uint_4 bases_offset;     /* Byte offset from start of file */
    uint_4 comments_size;    /* Number of bytes in Comment section */
    uint_4 comments_offset;  /* Byte offset from start of file */
    char version[4];         /* "version.revision", eg '3' '.' '0' '0' */
    uint_4 sample_size;      /* Size of samples in bytes 1=8bits, 2=16bits*/
    uint_4 code_set;         /* code set used (but ignored!)*/
    uint_4 private_size;     /* No. of bytes of Private data, 0 if none */
    uint_4 private_offset;   /* Byte offset from start of file */
    uint_4 spare[18];        /* Unused */
} Header;

For versions of SCF files 2.0 or greater (Header.version is `greater than' "2.00"), the version number, precision of data, the uncertainty code set are specified in the header. Otherwise, the precision is assumed to be 1 byte, and the code set to be the default code set. The following uncertainty code sets are recognised (but still ignored by our programs!).

0       {A,C,G,T,-}   (default)
1       Staden
2       IUPAC (NC-IUB)
3       Pharmacia A.L.F. (NC-IUB)
4       {A,C,G,T,N}   (ABI 373A)
5       IBI/Pustell
6       DNA*
7       DNASIS
8       IG/PC-Gene
9       MicroGenie