The 403 is a tabulator. It prints bills to customers and checks to vendors. It also prints sorted and totalled reports, similar to Excel's subtotal command.
What is the chief difference between a tabulator and a computer? Is it the stored program versus the wired control panel? Is it the faster internal speed of the computer? Is it the disk drive under program control versus a file of cards that require operator handling?

This is the stored programm card for a 403. Approximately 18" x 13", 17 lbs.

The built-in row and column structure of a spreadsheet program gives you an easy starting point for organizing a task. The 403 control panel did the same thing for tab operators.

It prints a line for each card in a file.

First Reading, Second Reading, and Third Reading. Each card can be read three times as it passes through the machine. Wire each card column (from 1 through 80) to the print position you want it to print in. Also wire amount fields to counter entries to accumulate totals.

The counter control hubs, which tell the counter whether to add or subtract. The data being added is wired from the reading station to the counter entry hubs. Each counter has either 2, 4, 6, or 8 decimal positions.

The comparing unit, for making equal/unequal comparisons. Each card's sort key is compared to the sort key of the following card. When the key changes, a total cycle is started. Similar to Excel's subtotal command.

Selectors perform the IF-THEN-ELSE branch function. A test impulse wired to the C (common) hub comes out the T (transferred) hub if the condition you are testing is true. It comes out the N (normal) hub if the condition is false. The condition you are testing usually comes from reading a card column and wiring that column to one of the pickup hubs (IPU or DPU).