The 370A and 371A replaced the earlier 370 and 371. What's the difference?

The 370A and 371A replaced the earlier 370 and 371. What's the difference?

The non-A models employed bubble memory storage for curves and setups. The A models have floppy drives and more storage for curves and setups.

For current Tektronix curve tracers, see Keithley I-V Tracer software for individual instruments, and Keithley Parametric Curve Tracer configurations.