View source for Hello world and hello Texas from Database

Install VistA with something like Astronaut. 
Get to a Mumps [[Prompt~|prompt:]] choose item 3 if you are using VistA Commander.
 
 MUMPS>write "hello world"
 hello world
 MUMPS>write "hello " write $P(^DIC(5,48,0),"^",1)
 hello TEXAS
 MUMPS>write "hello ",$$GET1^DIQ(5,48,0.01,,,"ZERROR")
 hello TEXAS

What the first hello TEXAS line does:

* Invokes the [[MUMPS Functions $PIECE|Mumps function $P[iece]]], which is similar to but not exactly like the substring command in many other languages.
* The ^ indicates that this is not a local variable; Mumps will look for a [[Global~|global]] stored on disk and visible to other users.
* The global DIC holds the [[File Of Files~|File of Files]], but ^DIC with the subscript 5 says to look in file 5 (The STATE File)
* The ^DIC(5, is followed by a 48, which means entry 48 in the STATE File.
* The ^DIC(5,48, is followed by 0 because the NAME Field is stored in node 0 and the first piece.
* Then $P uses the ^ in this case as a delimiter, and returns the first piece.
* Since ^DIC(5,48,0)="TEXAS^TX^48^^1^1", MUMPS writes "TEXAS".

What the second hello TEXAS line does:

* invokes a FileMan function named $$GET1^DIQ  which does the same thing as the first hello TEXAS line.
& the first argument is the number of the file as the source of data.