Excel formula to verify cell and skip to next row

it is possible the answer is "IF" statement. Here is the question.

Column A ABC ABC XYX XYX AAA

Column B 12 22 1 23 3

Column C If Cell A = ABC then display Column B, If Cell A doesn't = ABC then go to next row.

Question 1: I would like the formula to check A1, A2, etc. and return result in C1, C2, etc. with value equals to B1, B2.

Question 2: Just say A8 is the last entry. A9 is blank. Is there a formula to know to stop if A1 is blank and stop validation.