Tutorial: OR is not always two separate IFs

A OR B is true when at least one condition is true, including when both are true. A AND B requires both. An IF with an OR condition runs its body once when the condition is true; it does not run the body twice when both sides are true.

# Count students, not qualifying subject marks
Count = 0
for each score card X:
    if X.Mathematics > 90 OR X.Physics > 90:
        Count = Count + 1

# Different result: this counts successful subject tests
Count = 0
for each score card X:
    if X.Mathematics > 90:
        Count = Count + 1
    if X.Physics > 90:
        Count = Count + 1

In the actual scores, 6 students have Maths > 90 OR Physics > 90. Two independent increments produce 8 because Rahul and Deepika pass both tests. The extra 2 is the overlap. “Greater than 90” excludes exactly 90; do not silently change > to ≥.

You can count once using IF A … ELSE IF B … with the same increment, because B is then used only when A is false. But this structure is wrong if you want two separate subject counters that should both increase when both tests pass. Equivalent conditions alone do not make differently placed updates equivalent.