1-D arrays

A list of the same type

• An array holds a fixed number of values of one type.
• The guide's lower bound is 1 unless a question says otherwise.
• One index, in square brackets, picks an element.

DECLARE Score : ARRAY[1:5] OF INTEGER
Score[1] ← 4
Score[2] ← 8
OUTPUT Score[1]

A loop visits every cell

• A FOR loop from the lower bound to the upper bound is how you fill or read the array.

DECLARE Score : ARRAY[1:3] OF INTEGER
Score[1] ← 4
Score[2] ← 8
Score[3] ← 6
DECLARE Total : INTEGER
DECLARE I : INTEGER
Total ← 0
FOR I ← 1 TO 3
  Total ← Total + Score[I]
NEXT I
OUTPUT Total

Watch out

• Score[1] is the first cell when the array was declared [1:5].
• The index can be an expression: Score[I + 1].

Common mistakes

For a maximum search, a stored candidate represents the best item seen so far. Trace an all-negative array: an initial candidate that is not an array item can give a wrong result.

• Declare the array before you store into a cell.
• The index must stay inside the declared bounds.

Now you try

• Store three numbers and total them.

Independent transfer

The final task has no supplied algorithm. Plan its inputs, processing and outputs, then solve it before opening support. Check more than the sample case.