Data Source enhancement with ABAP....Explain

Hi,

Can any one please explain me what this code is performing

(Convert this machine language into human language in detail please)

This code is used in CMOD for enchancement of Transaction Data Source

Data: i_t_data like ZOXWRD0054.

case i_datasource.

when ' Z_TRM_LMS'.

Loop at c_t_data into i_t_data.

Select single bonus_cat perfinc active from ztrm_labdlycat into

(i_t_data-zzbonus, i_t_data-zzperf, i_t_data-zzactive)

Where locat = i_t_data-locat and

exrsn = i_t_data-exrsn and

apobj = i_t_data-apobj.

Modify c_t_data from i_t_data.

Endloop.

Endcase.

Thanks in advance