Conditional branch

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A conditional branch is an instruction in the CPU which is not always taken; whether it is taken or not depends on some test.

In moderm computers, conditional branches are usually implemented with condition codes, status bits set by previous arithmetic operations. By examining these bits, the complete complement of signed and unsigned conditional branches can be produced.

Example set

On the PDP-11, the rather complete set of conditional branches (copied in many machines since) includes:

  • BEQ - Zero, or equal (after comparing two quantities)
  • BNE - Non-zero, or not equal
  • BPL - Positive
  • BMI - Negative
  • BCS - Carry
  • BCC - No Carry
  • BVS - Overflow
  • BVC - No Oveflow

Signed:

  • BGE - Greater or Equal
  • BGT - Greater
  • BLE - Lesser or Equal
  • BLT - Lesser

Unsigned:

  • BLOS - Lower or the same
  • BLO - Lower
  • BHIS - Higher or the same
  • BHI - Higher