Point of sale or point of service (POS or PoS) can mean a retail shop, a checkout counter in a shop, or the location where a transaction occurs. More specifically, the point of sale often refers to the hardware and software used for checkouts -- the equivalent of an electronic cash register. Point of sale systems are used in supermarkets, restaurants, hotels, stadiums, and casinos, as well as almost any type of retail establishment.

Point-of-sale technology
POS systems evolved from the mechanical cash registers of the first half of the 20th century. Examples included the NCR registers, operated by a crank, and the lever-operated Burroughs registers. These cash registers recorded data on journal tapes or paper tape and required an extra step to transcribe the information into the retailer's accounting system.

Later cash registers moved to operation by electricity, such as the NCR Class 5 cash register. The first computer-based systems were introduced in 1973, such as the IBM 3653 Store System and the NCR 2150. Other computer-based manufacturers were Regitel, TRW, and Datachecker. 1973 also brought about the introduction of the UPC/EAN Barcode readers for POS systems. In 1986, the IBM 4683 introduced PC-based POS systems.

During the late 1980s and 90s, manufacturers developed stand-alone credit card devices to easily and securely add credit card processing to POS systems. Some popular models include the VeriFone Tranz 330, Hypercom T7 Plus, and Lipman Nurit 2085. These relatively simple devices have evolved to handle multiple applications (credit card processing, gift card activation, age verification, employee time tracking) on one device. Some wireless POS systems for restaurants not only allow for mobile payment processing, they also allow servers to process the entire food order right at tableside.

Most retail POS systems do much more than just "point of sale" tasks. Even for smaller tier 4 & 5 retailers, many POS systems can include fully integrated accounting, inventory management, open to buy forecasting, customer relation management (CRM), service management, rental, and payroll modules. Due to this wide range of functionality, vendors sometimes refer to POS solutions as retail management software or business management software.

Early POS software
The early electronic cash registers (ECR) were programmed in proprietary software and were very limited in function and communications capability. In August of 1973 IBM announced the IBM 3650 and 3660 Store Systems that were, in essence, a mainframe computer packaged as a store controller that could control 128 IBM 3653/3663 Point of Sale Registers. This system was the first commercial use of client-server technology, peer to peer communications, Local Area Network (LAN) simultaneous backup, and remote initialization. By mid-1974, it was installed in Pathmark Stores in New Jersey and Dillards Department Stores.

Programmability allowed retailers to be more creative. In 1979 Gene Mosher's Old Canal Cafe in Syracuse, New York was using POS software written by Mosher that ran on an Apple II to take customer orders at the restaurant's front entrance and print complete preparation details in the restaurant's kitchen. In that novel context, customers would often proceed to their tables to find their food waiting for them already. This software included real time labor and food cost reports.

POS hardware interface standardization
Vendors and retailers are working to standardize development of computerized POS systems and simplify interconnecting POS devices. Two such initiatives are OPOS and JavaPOS, both of which conform to the UnifiedPOS standard led by The National Retail Foundation.

OPOS, short for OLE for POS, was the first commonly-adopted standard and was created by Microsoft, NCR Corporation, Epson and Fujitsu-ICL. OPOS is a COM-based interface compatible with all COM-enabled programming languages for Microsoft Windows. OPOS was first released in 1996. JavaPOS was developed by Sun Microsystems, IBM, and NCR Corporation in 1997 and first released in 1999. JavaPOS is for Java what OPOS is for Windows, and thus largely platform independent.