Learn to Program with Small Basic

You start by initializing the sum variable (which holds the running
sum) to 0 (line 2). You then use a nested loop to iterate over all the rows
and columns (lines 3–4). For each iteration, you add the number stored in
sales[r][c] to sum (line 5). When the outer loop ends, you display the result
followed by K for thousands (line 8).
Add this subroutine to the program, and then add a statement to call it.
Here’s what you should see when you call the TotalSales() subroutine:
Total Sales: $1340 K
Step 2: Find the Sum of Each Column
Donald also wants to see the total sales for each Duckberg Industries product.
He needs to compare these numbers with those from his competitors
to assess his company’s market share.
To give Donald this information, you’ll use the ColumnSum() subroutine
in Listing 17-6 to compute the sum of each column in the sales matrix.
1 Sub ColumnSum
2 For c = 1 To COLS ' For each column
3 sum = 0 ' Initializes the sum for column c
4 For r = 1 To ROWS ' Iterates over the rows
5 sum = sum + sales[r][c] ' Adds number at row r, column c
6 EndFor
7 colName = product[c] + " Sales: $" ' Name to display
8 TextWindow.WriteLine(colName + sum + " K")
9 EndFor
10 EndSub
Listing 17-6: The ColumnSum() subroutine
You start the outer loop to iterate over the five columns (line 2). For
each column (each value of c), you initialize the column’s sum to 0 (line 3)
and then start a For loop to add the numbers from all the rows in that column
to sum (lines 4–6). When the inner loop completes, you get the name
of the current product (from product[c]), append "Sales: $" to it, and save
the resulting string in colName (line 7). In line 8, you display that string followed
by the sum you just computed. The outer loop then restarts to find
and display the sum for the next column.
Add this subroutine to the program, and then add a statement to call it.
Here’s what you should see when you call the ColumnSum() subroutine:
eShoes Sales: $190 K
iShirt Sales: $200 K
Shampoop Sales: $310 K
dWater Sales: $330 K
iHat Sales: $310 K
Expanding to Higher-Dimension Arrays 251