how to find data type of field dynamically in abap

hi all,

I am hanged up in one issue. There an internal table is filled.

theres one field ,and i want to extract the data type of the field content.

Ex. i_tab is internal table having field var1.

let the content of var1 have data type same as that of matnr (material no.)

so here i want to extract this data type.

thanx in advance for efficient help