# Problem
Which addressing modes are used in the following instructions?
1. `LDR r1, [r0]`.
2. `LDR r1, [r0, #4]`.
3. `LDR r1, [r0, #4]!`.
4. `LDR r1, [r0], #4`.
# Process
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# Answer
1. Register Indirect.
2. Register Indirect With Constant.
3. Pre-Indexed.
4. Post-Indexed.