Conditional Branch Instructions

Step 1: Understand the conditional branch instruction.
In most microprocessors, conditional branch instructions are used to alter the flow of execution based on certain conditions. These conditions are usually determined by the condition code flags (e.g., zero flag, carry flag) that are set during previous arithmetic or logic operations.

Step 2: Explanation of each option.
- **Option (1):** Correct. A conditional branch instruction checks the status of the condition code flag (set by previous instructions) and affects some flag registers based on the outcome of the condition.

- **Option (2):** Incorrect. Conditional branch instructions do check condition code flags.

- **Option (3):** Incorrect. Conditional branch instructions check the condition code flags and may modify some flags.

- **Option (4):** Incorrect. The instruction typically does not affect all flag registers, only those relevant to the branch condition.

Step 3: Conclusion.
The correct answer is option (1), as this correctly describes the behavior of conditional branch instructions in most microprocessors.