1) Pass 1 processes macro definitions by reading source code cards and entering macro names, parameters, and lines into a Macro Definition Table (MDT). 2) Pass 2 processes macro calls by searching for macro names in source code, expanding the macros by retrieving lines from the MDT and substituting arguments, and writing the expanded source code to a new file. 3) The process repeats until all macros are expanded.

1. Macro Processors
Flowcharts
Pass 1-Processing macro definitions
Pass 2-Processing macro calls and expansion

2. Pass 1
Pass 1 – processing macro definitions
MDTC<-1
MNTC<-1
Read next
source card
MACRO No
Write copy of
pseudo-
source card
op?
Yes
END
No
pseudo-
Read next
op?
source card
Yes
Enter macro name and Go to Pass 2
current value of MDTC Read next
in MNT entry number source card
MNTC
Substitute
index
MNTC <- MNTC + 1 notation for
arguments
Prepare argument list array
Enter line into MDT
Enter macro name card
into MDT MDTC <- MDTC + 1
MDTC <- MDTC + 1
MEND
pseudo-
Yes op? No

3. Pass 2
Pass 2 – processing macro calls and expansion
Read next
source card
(copied by
pass 1)
Search MNT for match
with operation code
MACRO No Write into
name expanded
found? source card
file
Yes
END
No
pseudo-
MDTP <- MDT index
op?
from MNT entry
Yes
Supply expanded
Set up argument list
source file to
array
assembler
processing
MDTP <- MDTP + 1
Get line from MDT
Substitute arguments
from macro call
MEND Write
pseudo- expanded
Yes op? source card
No