Condition Codes (sometimes called Return Codes) are simply a method to let the caller know how the program ended. The program itself sets the COND CODE prior to ending.
The degree of severity for certain errors conditions are typically related to the rising COND CODE.
0 = OK
4 = Informational
8 = Warning
12 = Error
16 = Severe error
Using a value that is a mutiple of 4 makes a handy "offset" into an array of BRANCH instructions, each of which use 4 bytes of machine code.
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