Also, when you switch to DOS, often times the file transfer or other process will stop because DOS is not a multitasking operating system. Some vendors have developed a workaround. As the PC becomes a partner with the mainframe, rather than a souped-up terminal, more sophisticated applications are possible. So for example, a loan application can be entered and verified on the PC, then sent to the mainframe. Mostly, APIs are used for far simpler tasks.
Users can automate simple tasks, such as downloading files.
Nearly all gateways have some type of programming interface, whether proprietary to that manufacturer or compatible with IBM's. They allow you to present information in a way different from the traditional mainframe. These APIs are popular because they do not require any changes to be made on the host side. APPC is used in applications where the PC or midrange is considered the peer of the mainframe. APPC is primarily used in high-end transaction processing applications, such as done in airline reservations or banks.