MACRO
&LAB     FACT   &REG,&N            parameters
&F       SETA   1                  f=1
&I       SETA   1                  i=1
.EA      AIF    (&I GT &N).EB      ea: if i>n then goto eb
&F       SETA   &F*&I              f=f*i
&I       SETA   &I+1               i=i+1
         AGO    .EA                goto ea
.EB      ANOP                      eb:
         MNOTE  0,'Load &REG with &N! = &F'   macro note
&LAB     L      &REG,=A(&F)        load reg with factorial
         MEND                      macro end
COMPCALB CSECT
         USING  COMPCALB,R12       base register
         LR     R12,R15            set base register
         FACT   R1,10              macro call
         XDECO  R1,PG
         XPRNT  PG,L'PG            print buffer
         BR     R14                exit
PG       DS     CL12
         YREGS
         END    COMPCALB