A quick answer for you Mwape!
The SEG-Y file format is one of several standards developed by the Society of Exploration Geophysicists for storing geophysical data. It has an open data specification, and is controlled by the SEG Technical Standards Committee.
It was originally developed in 1973 to store single-line seismic digital data on magnetic tapes. The "rev0" specification was published in 1975. However, since it's release, there have been significant advancements in geophysical data acquisition, such as 3-dimensional seismic techniques and high speed, high capacity recording.
The most recent revision of the SEG-Y format, "rev1", was released in 2002. It still features certain legacies of the original format, such as the 3200 byte data header and support for EBCDIC character encoding.
hope this helped,
Bill