SEC                        SEC Set carry flag                         SEC

  Operation:  1 -> C                                    N V - B D I Z C
                                                        . . . . . . . 1

  +----------------+-----------------------+---------+---------+----------+
  | Addressing Mode| Assembly Language Form| OP CODE |No. Bytes|No. Cycles|
  +----------------+-----------------------+---------+---------+----------+
  |  Implied       |   SEC                 |   $38   |    1    |    2     |
  +----------------+-----------------------+---------+---------+----------+

What it does: Sets the carry (C) flag (in the processor Status Register byte).

Major uses: This instruction is always used before any SBC operation to show if the result of the subtraction was negative (if the Accumulator contained a smaller number than the byte in memory being subtracted from it). See SBC.