OCRBlocks is a game played on a 5 x 5 grid - OCR - GCSE Computer Science - Question 6 - 2021 - Paper 1

The returned value is "B" since player B has placed a block at that coordinate.

The returned value is "FREE" as this position has not been filled by either player.

One feature that indicates checkblock() is a function is that it returns a value to the caller. Procedures typically do not return values.

The function call checkblock(-1, 6) will produce an error because the parameters -1 and 6 are outside the valid index range of the gamegrid array.

Validation can be added by checking if r (row) and c (column) are within the bounds of the array. For example:

if r < 0 or r >= 5 or c < 0 or c >= 5 then
   return "INVALID"
endif

This checks if the coordinates are valid before accessing the array.

1. Prompt the player for the position (r, c) of their block on the board.
2. Call checkblock(r, c) to check if the position is free.
3. If the return value is "FREE":
   • Update gamegrid[r][c] to "A".
4. If the return value is not "FREE":
   • Display a message indicating the position is taken.
   • Repeat steps 1-4 until a free position is chosen.