A 4x4 game board tracks the coordinates of a hidden item marked with the character 'T'. The rest of the board contains empty values marked with 'E' as shown in the grid below.
| Col 0 | Col 1 | Col 2 | Col 3 | |
|---|---|---|---|---|
| Row 0 | E | E | E | E |
| Row 1 | E | E | T | E |
| Row 2 | E | E | E | E |
| Row 3 | E | E | E | E |
for r in range(4):
for c in range(4):
if checkCell(r, c) == "T":
target_r = r
target_c = c
Explain the purpose of the first iteration structure (for r in range(4)) in this program.