Invoice and Sales Ledger

Two programs for a small business. The invoicing program keeps a file of up to 100 customers with four address lines each and produces numbered invoices: it prints a four-line letterhead, the invoice number, the date and the customer’s address, then takes item descriptions of up to 22 characters, each with a price, totals them and sends the screen to the printer with COPY. Its menu can also list every invoice on the printer with a grand total, and SAVE the invoice list for the ledger followed by the program itself, so the customers and invoice numbers carry over to the next session. The sales ledger loads that invoice list, gathers each customer’s invoices, lets you post dated payments, and shows invoice and payment totals and the outstanding balance for each customer, ending with the total outstanding. It then saves itself so the posted payments are kept.

From pages 33–39 (“Invoicing” and “Sales Ledger”) of Roger Valentine’s The Timex Sinclair 2068. The letterhead DATA lines hold placeholders.

Neither part carries a credit. They were CASH pt1 and CASH pt2 on a SNUG library disk, where the saved invoice and payment arrays were empty. They are different programs from the Invoice and Cash Flow programs elsewhere on this site.

Program Analysis

Invoicing (CASH pt1)

• Customers are held in a$(100,4,20), four 20-character address lines each, with the count in no. Each invoice keeps its date, the customer’s first address line and its total in o$(100,3,10), with the invoice count in in.
• Lines 60–85 show the menu: 1 Produce Invoice, 2 List Invoices, 3 SAVE.
• Lines 130–230 list the customers by number; 0 adds a new one, whose address lines are typed at INPUT AT positions.
• Line 240 READs the letterhead from DATA lines 90–120 and centres each line with (32-LEN t$)/2. Lines 250–350 take the date and the items, and lines 360–410 show the total with “C= COPY :X= CANC.”.
• Lines 420–490 LPRINT the date, customer and total of every invoice and a grand total.
• Lines 500–540 save o$() as "INVOICES" DATA, then the program as "INVOICING" LINE 50, which skips the DIM statements so the customer file survives.

Sales Ledger (CASH pt2)

• Line 80 loads "INVOICES" DATA o$(). Payments are kept in p$(100,3,10) (date, customer, amount) with the count in np.
• Lines 90–520 take each invoice in turn. The customer name is overwritten with “x” once it has been handled, a blank name marks the end of the list, and the inner loop at lines 180–250 collects that customer’s other invoices.
• Lines 260–400 list the customer’s earlier payments and offer to post new ones. Lines 410–470 print the totals and the outstanding (“O/S”) balance, worked out in whole cents in line 460 to avoid rounding errors.
• Line 570 saves the program as "SALES" LINE 40, which keeps the payments array and reloads the invoice list on the next run, then ends with GO TO 9999, a line that does not exist.

Money Formatting

The subroutine at line 550 (line 580 in the ledger) formats an amount in an eight-character fixed-length string m$. It assigns STR$ p, which is left-aligned and padded with spaces, moves it right until the last character is not a space, then adds “.00” or a final “0” as needed. If the decimal point does not end up in position 6, the subroutine sets x, and the price prompt asks again, which rejects amounts with more than two decimal places.

Notable Techniques

• Saving the program with SAVE … LINE to a line after the DIM statements keeps the customer file and the payments with the program, while SAVE … DATA passes the invoice list from one program to the other.
• Assigning to a fixed-length DIM string pads and truncates automatically, which the money subroutine uses to align amounts.
• Invoices are printed with COPY, after the prompt line is blanked by printing a 32-space string over it.

Potential Issues

• Line 390 offers “C= COPY” but accepts a capital C or a lower-case o; a lower-case c does nothing.
• X (“CANC.”) starts the same invoice again rather than cancelling it. The only way back to the menu from an invoice is C, which prints it.
• After the second SAVE in line 540 the program runs on into the money subroutine, which appears to end with “7 RETURN without GO SUB”. Both files have been saved by then.
• An invoice stores only the first 10 characters of the customer’s first address line, and the ledger groups invoices by that, so two customers whose names begin with the same 10 characters would be merged.
• Whole-number amounts of 100,000 or more appear to lose their leading digit instead of being rejected.
• Nothing checks the limits of 100 customers, 100 invoices or 100 payments. The ledger’s column heading is misspelled “PAYNENTS”.

Both programs came from an Oliger (JLO SAFE) disk and were converted for tape. The letterhead lines now hold placeholder text. Three bugs were repaired: menu option 3 could not be reached because line 85 tested for “2” instead of “3”; line 520 had a colon before DATA, which made it save the program instead of the invoice list; and the ledger’s lines 160–170 used an undefined variable a where q was meant, which stopped it with “2 Variable not found”. The tape starts with a short menu that loads either part, and ends with a small sample INVOICES file of three invoices for two made-up customers so the ledger has something to load. It was tested in ZEsarUX: the menu, an invoice for a sample customer with two items, the ledger with a posted payment, and the SAVE option.