A computer program product for executing a machine instruction in a central processing unit, the computer program product comprising: a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: obtaining, by a processor, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising: at least one opcode field to provide an opcode; a register field to be used to designate a register (Ri), the register comprising a first operand; and at least one field for indicating a location of a second operand, the second operand comprising a starting address of the block of main memory, and characterised in that the opcode identifies a Load Count to Block Boundary operation, the Load Count to Block Boundary operation to compute a distance from a location in main memory to a boundary of a block of main memory and in that the method further comprises executing the machine instruction to perform the Load Count to Block Boundary operation, the execution comprising: determining the distance from the location of the second operand to the boundary of the block of main memory, the determining the distance comprising counting by the processor the number of bytes from the location of the second operand to the boundary of the block of memory; and placing a value representing the distance in the first operand, the value being a result of executing the Load Count to Block Boundary operation. obtaining, by a processor, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising: at least one opcode field to provide an opcode; a register field to be used to designate a register (Ri), the register comprising a first operand; and at least one field for indicating a location of a second operand, the second operand comprising a starting address of the block of main memory, and characterised in that the opcode identifies a Load Count to Block at least one opcode field to provide an opcode; a register field to be used to designate a register (Ri), the register comprising a first operand; and at least one field for indicating a location of a second operand, the second operand comprising a starting address of the block of main memory, Boundary operation, the Load Count to Block Boundary operation to compute a distance from a location in main memory to a boundary of a block of main memory and in that the method further comprises executing the machine instruction to perform the Load Count to Block Boundary operation, the execution comprising: determining the distance from the location of the second operand to the boundary of the block of main memory, the determining the distance comprising counting by the processor the number of bytes from the location of the second operand to the boundary of the block of memory; and placing a value representing the distance in the first operand, the value being a result of executing the Load Count to Block Boundary operation. determining the distance from the location of the second operand to the boundary of the block of main memory, the determining the distance comprising counting by the processor the number of bytes from the location of the second operand to the boundary of the block of memory; and placing a value representing the distance in the first operand, the value being a result of executing the Load Count to Block Boundary operation.