Multiple answers.

Which of the following interrupt service requests are initiated from software $($i$.$e$.,$ exception or trap$)?$

Timer generated an interrupt so that the operating system switches between processes.

The computer lacks enough memory to allow a program continue its execution.

The program counter of the CPU jumps to an illegal address.

During the interrupt service of the hard disk, an illegal instruction is executed.

The direct memory access unit has finished the transfer of data from device controller to the memory and informs CPU.

The user program asks operating system to perform an I$/$O operation on its behalf.