What Pseudo Code Is

• Informal, high-level description of an algorithm's logic using structured English + programming constructs (loops, conditionals, assignments) — not tied to any specific language's syntax
• Bridges the gap between natural-language algorithm description and actual source code

Common Conventions

BEGIN
  READ n
  SET sum = 0
  FOR i = 1 TO n DO
     sum = sum + i
  END FOR
  PRINT sum
END

• Keywords like BEGIN/END, IF/THEN/ELSE, WHILE, FOR, READ/PRINT used consistently but loosely
• Indentation shows nesting/control flow, like real code

Why It's Used

• Language-independent — focuses reviewer's attention on logic, not syntax errors
• Easier to translate into any programming language (C++, Python, Java) once the logic is verified
• Standard tool for algorithm design/communication in textbooks, interviews, and CSS papers

Exam Angle

When asked to "write an algorithm" in the CS-optional paper, pseudo code (not full C++ syntax) is usually the expected answer format — focus on clear structured steps over compilable syntax.

📌 Sample & Repeated FPSC Questions (2016–2026)

2026, Paper I, Q3(c) (8 marks) — Write pseudocode to reverse an array using pointers.

Function ReverseArray(arr, n):
    left  <- pointer to arr[0]           // first element
    right <- pointer to arr[n-1]         // last element

    while left < right:                  // pointers haven't crossed
        temp   <- *left
        *left  <- *right
        *right <- temp
        left   <- left + 1
        right  <- right - 1

    return arr

Key reasoning points:

• Two pointers converge from opposite ends, swapping as they move — runs in O(n) time using only O(1) extra space (in-place, unlike copying into a new reversed array).
• Loop invariant: at every iteration, everything outside [left, right] is already correctly reversed.
• Equivalent C++: int* left = arr; int* right = arr + n - 1; inside the same swap-and-converge while loop.