The first step in the algorithm to calculate the positive difference between two given values, x and y, is to declare the variable Diff. This is essential as it initializes the variable that will be used to store the calculated difference between x and y. The subsequent steps involve conditional statements and arithmetic operations that utilize this declared variable to compute and store the positive difference. References: N/A (as per image provided) The image shows steps of an algorithm listed in no particular order for calculating the positive difference between two values, making it relevant for understanding or teaching algorithmic logic and sequence.