**************************************************************
** HELLO - Program to print "Hello, World" on device 009 **
**************************************************************
| HELLO | CSECT | ||
| STM | R14,R12,12(R13) | Save Registers | |
| LR | R12,R15 | Load Base Register | |
| USING | HELLO,R12 | Establish Addressability | |
| SSM | =X'00' | Disable Interrupts | |
| SPKA | 0(0) | Disable storage protection | |
| LA | R2,CCWS | Store pointer to CCW chain | |
| ST | R2,CAW | ... in Channel Address Word | |
| LA | R2,9 | Put device address in R2 | |
| CLEARIO | TIO | 0(R2) | Test for device busy |
| BC | CC1+CC2,CLEARIO | Wait until device not busy | |
| BC | CC3,IOERROR | Abort if device error | |
| STARTIO | SIO | 0(R2) | Start I/O to the console |
| BC | CC1,CSWSTORE | A CSW Has been stored | |
| BC | CC2,CLEARIO | Device busy. Wait until clear | |
| BC | CC3,IOERROR | Abort if device error | |
| TESTIO | TIO | 0(R2) | Wait for I/O completion |
| BC | CC2,TESTIO | Busy, Wait for completion | |
| BC | CC3,IOERROR | Abort if device error | |
| CSWSTORE | CLI | CSW+4,CE | Channel End w/o Device End? |
| BE | TESTIO | Yes - wait for Device End too | |
| TM | CSW+4,BY | Channel Busy? | |
| BO | TESTIO | Yes - Keep Waiting | |
| TM | CSW+4,DE | Device End? | |
| BNO | IOERROR | No - The CSW is bad | |
| SUCCESS | SSM | =X'FF' | Reenable Interrupts |
| LM | R14,R12,12(R13) | Restore Caller's Registers | |
| XR | R15,R15 | Clear Return Code | |
| BR | R14 | Return to Caller | |
| IOERROR | SSM | =X'FF' | Reenable Interrupts |
| LM | R14,R12,12(R13) | Restore Caller's Registers | |
| LA | R15,4 | Set Return Code 4 | |
| BR | R14 | Return to Caller | |
| DS | 0D | CCW must be doubleword aligned | |
| CCWS | CCW | X'09',MESSAGE,X'20' | ,L'MESSAGE |
| MESSAGE | DC | C'Hello, World' | |
| CSW | EQU | X'40' Addre | ss of Channel Status Word |
| BY | EQU | X'10' Chann | el Busy |
| CE | EQU | X'08' Chann | el End |
| DE | EQU | X'04' Devic | e End |
| CAW | EQU | X'48' Addre | ss of Channel Address Word |
| R2 | EQU | 2 Regis | ter 2 |
| R12 | EQU | 12 Regis | ter 12 |
| R13 | EQU | 13 Regis | ter 13 |
| R14 | EQU | 14 Regis | ter 14 |
| R15 | EQU | 15 Regis | ter 15 |
| CC0 | EQU | 8 Condi | tion Code 0 |
| CC1 | EQU | 4 Condi | tion Code 1 |
| CC2 | EQU | 2 Condi | tion Code 2 |
| CC3 | EQU | 1 Condi | tion Code 3 |
| END |
The only part of that post that remotely qualifies as modern is the mixed-case comments, which were likely added later on a 3270l, probably using the likes of XEDIT, some time in the 80's. XEDIT was a creature of CP/CMS, a virtual operating system which allowed one to run privileged code such as your example without needing exclusive use of an expensive mainframe. Using CP/CMS, you could treat a mainframe as if it were a PC.
Looks like there was a tabbing problem down in those EQUs. Still assembles due to a white space break, but it's ugly.
w "Hello world"