The following function printstr prints a character string whose starting address is in the accumulator.  It prints characters in reverse order in each word of memory, continuing with sebsequent words of memory, until a byte of 0s indicates end-of-string.  The contents of the accumulator are lost.

Suppose, at addresses 12 and 13, we have the assembly lines
   C 'ABCD'
   C 'EF'
Then addresses 12 and 13 will contain the characters
12:   DCBA
13:   \\FE
where \ means a byte of 0s.  Calling printstr with address 12 in the accumulator will print the 6 characters ABCDEF .

psC3: I 3
psc: W 1
pszs: B 0
pst: W 1
psC1: I 1
psC256: H 100
printstr: W 1
psL0: STA psadr
   LDA psC3
   STA psc
psadr: W 1 will be LDA
psL1: IOR pszs
   BZE psdone
   OUT opsys
   STA pst
   LDA psc
   IOR pszs
   BZE psnxtwd
   SUB psC1
   STA psc
   LDA pst
   DIV psC256 shift right
   BUN psL1
psnxtwd: LDA psadr
   ADD psC1
   BUN psL0
psdone: BIN printstr