Arrays

A FOR loop is the natural way to visit every element of an array in turn. The counter variable becomes the index.

DECLARE Index : INTEGER
FOR Index ← 1 TO 5
   OUTPUT Scores[Index]
NEXT Index

This prints every element of Scores in turn:

12
100
5
2
8

Common array-processing patterns

Sum every element of a numeric array:

DECLARE Total : INTEGER
Total ← 0
FOR Index ← 1 TO 5
   Total ← Total + Scores[Index]
NEXT Index
OUTPUT "Total: ", Total

Find the largest element (assumes at least one element exists):

DECLARE Highest : INTEGER
Highest ← Scores[1]
FOR Index ← 2 TO 5
   IF Scores[Index] > Highest THEN
      Highest ← Scores[Index]
   ENDIF
NEXT Index
OUTPUT "Highest: ", Highest

Count how many elements satisfy a condition (e.g. count pass marks ≥ 50):

DECLARE Passes : INTEGER
Passes ← 0
FOR Index ← 1 TO 30
   IF Marks[Index] >= 50 THEN
      Passes ← Passes + 1
   ENDIF
NEXT Index
OUTPUT "Number of passes: ", Passes

Search for a value (linear search, topic 20):

DECLARE Found : BOOLEAN
Found ← FALSE
FOR Index ← 1 TO 30
   IF Marks[Index] = Target THEN
      Found ← TRUE
      OUTPUT "Found at position ", Index
   ENDIF
NEXT Index
IF Found = FALSE THEN
   OUTPUT "Not found"
ENDIF

Storing the array size in a variable

Real algorithms usually need to know the array's size at run time, not as a hard-coded number. A common idiom:

DECLARE Size : INTEGER
Size ← 30
DECLARE Marks : ARRAY[1:Size] OF INTEGER

FOR Index ← 1 TO Size
   OUTPUT Marks[Index]
NEXT Index

Now if the class size changes, only the line Size ← 30 needs to be edited.