ICS331 Homework Assignment #3

ICS 331: System Software (981)

Homework # 3

Date: Novomber 17, 1998 Due Date: Novomber 24, 1998

Question 1 (3- pp. 218) (26 Points)

One method of eliminating the displaying the expansions of macros from the listing file is as follows:

When the macro processor encounters a macro invocation statement, it writes that statement with a special symbol, e. g. +, in column 1 in the source
file without expansion. Later when the assembler assemble that statement, which is recognized by the special symbol in column 1, it does two things:

it writes the statement in the listing file, and
it searches the DEFTAB for the definition of that macro and uses the actual arguments to generate the appropriate object code. This process is
repeated for each macro invocation statement.

So, the process of expanding a macro is done by the assembler not the macro processor.

Question 2 (3- pp. 220) (22 Points)

To include the generation of unique labels we need to modify procedure GETLINE in the algorithm of Figure 4.5 as follows: (modification is shown in bold)

Procedure GETLINE

begin

if EXPANDING then

begin

get next line of macro definition from DEFTAB

substitute arguments from ARGTAB for positional notation

if there is a label which starts with $ then

replace the $ in that label by $ZZ*

end {if}

else

read next line from input file

end{GETLINE}

* ZZ is a two character prefix that changes with each new invocation of the macro. It can be generated either in procedure GETLINE or in procedure
EXPAND

Question 3 (12- pp. 222) (32 Points)

a) RDBUFF F1, BUFFER, LENGTH, (04,12)

30		CLEAR	X	CLEAR LOOP COUNTER
35		CLEAR	A
45		+LDT	#4096	SET MAX LENGTH = 4096
50	$AALOOP	TD	=X'F1'	TEST INPUT DEVICE
55		JEQ	$AALOOP	LOOP UNTIL READY
60		RD	=X'F1'	READ CHARACTER INTO REGISTER A
65		COMP	=X'000004'
70		JEQ	$AAEXIT
65		COMP	=X'000012'
70		JEQ	$AAEXIT
75		STCH	BUFFER,X	STORE CHARACTER IN BUFFER
80		TIXR	T	LOOP UNLESS MAXIMUM LENGTH
85		JLT	$AALOOP	HAS BEEN REACHED
90	$AAEXIT	STX	LENGTH	SAVES RECORD LENGTH

b) LABEL RDBUFF F1, BUFFER, LENGTH, 00

30	LABEL	CLEAR	X	CLEAR LOOP COUNTER
35		CLEAR	A
45		+LDT	#4096	SET MAX LENGTH = 4096
50	$AALOOP	TD	=X'F1'	TEST INPUT DEVICE
55		JEQ	$AALOOP	LOOP UNTIL READY
60		RD	=X'F1'	READ CHARACTER INTO REGISTER A
75		STCH	BUFFER,X	STORE CHARACTER IN BUFFER
80		TIXR	T	LOOP UNLESS MAXIMUM LENGTH
85		JLT	$AALOOP	HAS BEEN REACHED
90	$AAEXIT	STX	LENGTH	SAVES RECORD LENGTH

Question 4 (19- pp. 223) (20 Points)

a) RDBUFF F3, BUF, RECL, ZZ {illegal value specified for &EOR}

        This error will be detected by the assembler during the assembly of line 40 since ZZ is not a hexadecimal digit.

            40 LDCH =X'ZZ'

b) RDBUFF F3, BUF, RECL, 04, 2048, 01 {too many arguments}

        This error will be detected by the macro processor during the one-to-one mapping of actual arguments and parameters

c) RDBUFF F3, , RECL, 04 {no value specified for &BUFADR}

        This error will be detected by the assembler during the assembly of line 40

            75 STCH ,X {&BUFADR is null}

d) RDBUFF F3, RECL, BUF {arguments specified in wrong order}

        This error will be detected by the macro processor during the one-to-one mapping of actual arguments and parameters