Stepping (debugging)

This allows the programmer to evaluate the effects of each statement or instruction in isolation, and thereby gain insight into the behavior (or misbehavior) of the executing program.

For this to be possible, three things are required: On the IBM System 360 processor range announced in 1964, these facilities were provided by front panel switches, buttons and banks of neon lights.

This led to the development of proprietary software from several independent vendors that provided similar features but deliberately restricted breakpoints and instruction stepping to particular application programs in particular address spaces and threads.

The program state (as applicable to the chosen application/thread) was saved for examination at each step and restored before resumption, giving the impression of a single user environment.

For this reason, the widespread use of these full screen animators in the mainframe world had to await the arrival of transaction processing systems - such as CICS in the early 1970s and were initially limited to debugging application programs operating within that environment.