One name, many values.

Declaring an array.

The declaration gives the identifier, the range of indexes and the data type of every element.

DECLARE Scores : ARRAY[1:5] OF INTEGER
Scores[1] ← 12
Scores[2] ← 7
Scores[3] ← 15
Scores[4] ← 9
Scores[5] ← 11
OUTPUT Scores[3]

This outputs 15, the value in element 3.

• Fixed length: ARRAY[1:5] has exactly 5 elements, indexes 1 to 5.
• Same data type: every element of Scores is an INTEGER.
• Why use one: one identifier instead of many variables, and loops can process every element with the same few lines.

The same idea in Python (for comparison only: the exam uses pseudocode)

scores = [12, 7, 15, 9, 11]    # a Python list; the first index is 0
print(scores[2])               # 15, the third element

Arrays and loops.

In the lab, choose Maximum and minimum. Six scores are input into an array by one loop, and a second loop compares each element with the largest and smallest so far.

DECLARE Temps : ARRAY[1:7] OF REAL
DECLARE Day : INTEGER
DECLARE Total : REAL
FOR Day ← 1 TO 7
    INPUT Temps[Day]
NEXT Day
Total ← 0
FOR Day ← 1 TO 7
    Total ← Total + Temps[Day]
NEXT Day
OUTPUT "Average: ", Total / 7

The same idea in Python (for comparison only: the exam uses pseudocode)

temps = []
for day in range(7):
    temps.append(float(input()))
print("Average:", sum(temps) / 7)

Using the index.

The index can be any expression that gives an integer, so a program can search an array, or move values between neighbouring elements, such as Names[Count + 1].

DECLARE Found : BOOLEAN
DECLARE Index : INTEGER
DECLARE Target : INTEGER
INPUT Target
Found ← FALSE
Index ← 1
WHILE Found = FALSE AND Index <= 5 DO
    IF Scores[Index] = Target
      THEN
        Found ← TRUE
      ELSE
        Index ← Index + 1
    ENDIF
ENDWHILE
IF Found = TRUE
  THEN
    OUTPUT "Found at position ", Index
  ELSE
    OUTPUT "Not found"
ENDIF