= i. 4 NB. create an Identity matrix of size 4
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1
makeI=: =@i. NB. define as a verb with a user-defined name
makeI 5 NB. create an Identity matrix of size 5
1 0 0 0 0
0 1 0 0 0
0 0 1 0 0
0 0 0 1 0
0 0 0 0 1