The indie store i worked in was a Chart Return shop.
This meant that we gave our sales data to whoever compiled the charts at the time. During my time it moved from The British Market Research Bureau, to Gallup to CIN to Millward Brown. Initially it was via Pen and paper, but then they introduced computers. Every record has a catalogue number and all you had to do was type this number into the machine and press enter. If you flick through your record collection you will notice that Catalogue numbers changed in the late 80s to accommodate this. There were less nonsensical numbers and letters like epc345278 and more short straight forward wordy ones like BONG3 or FIC 42. It made it easier for sales staff to remember and type them out. You will also notice that once these machines moved away from typed in data to barcode wands, the catalogue numbers on your records dropped letters all together and stuck to really long numbers instead.
But God forbid anyone should forget to type a sale in back then. Anything to make sure you did, anything to make it easy. One miss type would be classed as a missed sale for a record company and every entry was important. Which made any shop contibuting to the top 40 of interest to a record company.
Each night when you closed the shop you had to remember to turn the machine off. In retrospect i now know that by turning it off i was actually flicking it over to a fax like modem that would answer the phone and send the days data direct to Gallup. If you had forgotten to turn it off it couldn't communicate with their main computer and nothing was sent. Sometime during the night Gallup would call, collect the data and add it to that collected from all the other shops on the panel. The charts were actually compiled on a daily basis and they even released a mid week chart to the record companies so they could see how well (or bad) their singles and albums were doing so far that week.
It cost money to rent these little computers and in the end you also had to pay to have your own data sent back to you in chart form. But it was worth every penny. The deals and free stock you received from record companies, just because you were on the chart return panel, far outweighed anything they charged.
One rep once told me in the 80s that they could always tell who was on the chart panel without even going to the shop. All they had to do was ring them at night. If the machine answered the phone they knew they were worth a visit.