On 2/6/2013 4:26 PM, Lindy Mayfield wrote:
Is there ever a "need" to write an SVC? Or to put it another way, is there sometimes a need to get OS services from a problem state program like in an SVC? And if so, are PC routines the new way?
If you are writing new code, PC is the preferred method. If you just want to experiment, writing an SVC is interesting and educational.
Were once SVC's ok, and now they are not preferred?
When the S/360 was new, the available systems offered no practical way to perform some authorized functions from applications except by SVC, or the less desirable method of source changes to the system. Many installations implemented SVCs that changed a program state to key 0 or supervisor state, something that presented a security exposure. IBM eventually introduced authorized programs and the MODESET facility, then later the PC and related instructions. Gerhard Postpischil Bradford, Vermont
