1. A method of executing instructions in a computer system on operands containing a plurality of packed objects in respective lanes of the operand wherein each instruction defines an operation and contains a condition setting indicator settable independently of the operation, the method comprising: determining the status of the condition setting indicator and, when the condition setting indicator is set; carrying out an operation specified in the instruction on each lane of the operand and generating a set of multibit condition codes depending on the results of carrying out the operation for each lane.