Being tied to the future products of a vendor due to the previous investment made in that vendor's proprietary hardware or software. The most common vendor lock-in is the operating system. When custom programs are written for a specific operating system, it is time consuming and costly to convert those programs to another platform.
Lock-In by Format
If an application creates a proprietary data format that no other software recognizes, the customer is forced to use that program and its successors or absorb the expense of having the data converted to a more common format.
Lock-In by Habit
One of the most common vendor lock-ins is experience. After years of working with a software application and being very familiar with its nuances, it is psychologically difficult to embrace a different user interface on another program. Lock-in by habit is perhaps the most insidious lock-in, because there is no technical reason not to switch.
Lock-In by Programming Language
Although programming languages are generally not proprietary, the investment made in source code can be substantial over time. Converting to another language can be difficult and costly.
This term dates back many years and refers to vendors creating strange plugs and sockets that are not easily manufactured in order to prevent compatible equipment to come to market. See vendor neutral
and vendor interoperability