How the tape works
Each line of the tape is one entry. A plain number or a number starting with + is added to the running total, and a number starting with − (or -) is subtracted. A line starting with × (or * or x) multiplies the running total, and ÷ (or /) divides it.
S on its own line prints a subtotal without changing anything. T (or =) prints a total and starts a fresh section at zero, and the grand total adds up every section. Any words after a number stay on the tape as a note, which is handy for receipts and expense lists.
| Type | Meaning |
|---|---|
| 125.50 or + 125.50 | Add to the running total |
| - 18.75 | Subtract |
| × 2 or * 2 | Multiply the running total |
| ÷ 4 or / 4 | Divide the running total |
| S | Print a subtotal |
| T or = | Print a total and start a new section |
Worked example
The default tape is 125.50 groceries, + 42.25, − 18.75 refund, S, × 2, T, then + 0.10 and + 0.20.
Running totals: 125.50 → 167.75 → 149.00. The subtotal prints 149.00. Multiplying by 2 gives 298.00, and T prints that total and resets the tape. The new section is 0.10 + 0.20 = 0.30, so the grand total is 298.00 + 0.30 = 298.30.
Exact decimals and order of operations
Many calculators store numbers in binary floating point, which is why 0.1 + 0.2 can show 0.30000000000000004. This tape uses exact decimal arithmetic, so money adds up to the cent. Addition, subtraction and multiplication are exact; division is rounded to 20 decimal places.
Like a real adding machine, entries apply strictly in tape order. × 2 doubles everything above it, not just the previous number. For formulas with brackets or precedence, use the scientific calculator instead.