Data 88 - Wedding letter code dd = data definition to dd of word address --. giving address space

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Below,    
explains  key word concepts --> 

Wedding letter code
.....dd = data definition to 
.....dd of word address --. giving
...address space

OS/360 and successors - Wikipedia

https://en.wikipedia.org/wiki/OS/360_and_successors

IBM eventually renamed these options and made some significant design changes: Single Sequential Scheduler (SSS). Option 1; Primary Control Program (PCP). Multiple Sequential Schedulers (MSS). Option 2;
 Multiprogramming with a 
Fixed number of Tasks (MFT); 
MFT 2. Multiple Priority Schedulers (MPS). Option 4 ...

End  explanation 
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