From the principles of operation: Operands are signed and 32 bits long. 
Negative quantities are held in two's-complement form. 
<br>'''Multiplication:'''<br>
The product of the multiplier (the second operand) and the multiplicand 
(the first operand) replaces the multiplicand. Both multiplier and 
multiplicand are 32-bit signed integers. The product is always a 64-bit 
signed integer and occupies an even/odd register pair.
<br>'''Division:'''<br>
The dividend (first operand) is divided by the divisor (second operand) 
and replaced by the quotient and remainder. The dividend is a 64-bit 
signed integer and occupies the even/odd pair of registers. 
A 32-bit signed remainder and a 32-bit signed quotient replace the dividend 
in the even-numbered and odd-numbered registers, respectively.
The sign of the quotient is determined by the rules of algebra. 
The remainder has the same sign as the dividend.
*        Arithmetic/Integer        04/09/2015
ARITHINT CSECT
         USING  ARITHINT,R12
         LR     R12,R15
ADD      L      R1,A
         A      R1,B               r1=a+b
         XDECO  R1,BUF
         MVI    BUF,C'+'
         XPRNT  BUF,12
SUB      L      R1,A
         S      R1,B               r1=a-b
         XDECO  R1,BUF
         MVI    BUF,C'-'
         XPRNT  BUF,12
MUL      L      R1,A 
         M      R0,B               r0r1=a*b
         XDECO  R1,BUF             so r1 has the lower part
         MVI    BUF,C'*'
         XPRNT  BUF,12
DIV      L      R0,A
         SRDA   R0,32              to shift the sign
         D      R0,B               r1=a/b and r0 has the remainder
         XDECO  R1,BUF             so r1 has quotient
         MVI    BUF,C'/'
         XPRNT  BUF,12
MOD      L      R0,A
         SRDA   R0,32              to shift the sign
         D      R0,B               r1=a/b and r0 has the remainder
         XDECO  R0,BUF             so r0 has the remainder
         MVI    BUF,C'R'
         XPRNT  BUF,12
RETURN   XR     R15,R15
         BR     R14
         CNOP   0,4
A        DC     F'53'
B        DC     F'11'
BUF      DC     CL12' '
         YREGS
         END    ARITHINT
Inputs are in the code: a=53, b=11