Load upper immediate : Places the 16-bit immediate into the upper 16 bits of $t1 and clears the lower 16 bits to 0. Used to build a full 32-bit constant: first 'lui $t1,upper16' then 'ori $t1,$t1,lower16'. Example: to load 0x12345678 use 'lui $t1,0x1234' then 'ori $t1,$t1,0x5678'.