Simplify the following text for a Grade 10 native English-speaking person.
Original: A one instruction set computer ( OISC ) , sometimes called an ultimate reduced instruction set computer ( URISC ) , is an abstract machine that uses only one instruction â `` obviating the need for a machine language opcode .
Simplified: A One Instruction Set Computer ( OISC ) is an abstract computer that uses only one instruction ( with no need for a machine language opcode ) .