Is this the structure of the dat files?

struct l1ctl_burst_ind {
uint32_t frame_nr;
uint16_t band_arfcn;    /* ARFCN + band + ul indicator               */
uint8_t chan_nr;        /* GSM 08.58 channel number (9.3.1)          */
uint8_t flags;          /* BI_FLG_xxx + burst_id = 2LSBs             */
uint8_t rx_level;       /* 0 .. 63 in typical GSM notation (dBm+110) */
uint8_t snr;            /* Reported SNR >> 8 (0-255)                 */
uint8_t bits[15];       /* 114 bits + 2 steal bits. Filled MSB first */
} __attribute__((packed));

what does packed mean?