SLR 19 – Thinking ahead 120. OCR A Level (H046-H446) SLR19 – 2.1 Identify inputs & outputs 121. OCR A Level (H046-H446) SLR19 – 2.1 Determining preconditions 123. OCR A Level (H046-H446) SLR19 – 2.1 Reusable components 122. OCR A Level (H446) SLR19 – 2.1 Caching