ALCCS

 

Code: CS22 Subject: SYSTEM SOFTWARE

Flowchart: Alternate Process: MARCH 2010Time: 3 Hours Max. Marks: 100

 

NOTE:

      Question 1 is compulsory and carries 28 marks. Answer any FOUR questions from the rest. Marks are indicated against each question.

      Parts of a question should be answered at the same place.

 

 

 

Q.1 a. Explain context-free grammer with the help of a suitable example.

 

b. Differentiate between Linking loader and Linkage editor.

c. How is forward reference resolved in single-pass assembler?

 

d. Write a macro that swaps two variables.

 

e. List the features of Operator-Precedence Parsing.

 

f. Give a regular expression for all strings of a real number and a real number with optional fraction.

 

g. What are machine-Dependent features in assembly language? (7 4)

 

Q.2 a. Assemble the following program manually, showing the resultant machine code and symbol table (Instruction set table is given at the end)

 

START

101

 

READ

N

 

MOVER

BREG, ONE

 

MOVEM

BREG, TERM

AGAIN

MULT

BREG, TERM

 

MOVER

CREG, TERM

 

ADD

CREG, ONE

 

MOVEM

CREG, TERM

 

COMP

CREG, N

 

BC

LE, AGAIN

 

MOVEM

BREG, RESULT

 

PRINT

RESULT

 

STOP

 

N

DS

1

RESULT

DS

1

ONE

DC

1

TERM

DS

1

 

END

 

 

 

 

b. Describe two methods for collision handling. (12+6)

Q.3 a. What is the aim of code optimization? How is it achieved? Explain two phases of optimization using suitable examples.

b. What are the different phases of a compiler? Explain briefly each phase. (9+9)

 

Q.4 a. Give a parse tree and an AST for the source string a+b*c according to the following grammer rules

E::=T+E|T

T::=T *V|V

V::= <id>

b. Write an algorithm for nave top-down parsing

c. Discuss various categories of statement used in assembly language. (6+6+6)

 

Q.5 a. What is a command dialog? Explain various ways to implement command dialogs. List seven principles to ensure the effectiveness of command dialogs.

 

b. Explain Overlay structured program. (12+6)

Q.6 a. What is an absolute loader? Explain its role, advantages and disadvantages in brief.

b. Differentiate between a macro call and a procedure call.

c. Explain various Data Structures used by One-Pass Macro Processor. (6+6+6)

 

Q.7 a. What is an interpreter? How is it different from a compiler? What is the difference between pure and impure interpreters?

 

b. What is an interactive editor? Describe structure of an editor and its various types. (10+8)

 

Instruction Set Table

Symbol

Instruction opcode

STOP

00

ADD

01

SUB

02

MULT

03

MOVER

04

MOVEM

05

COMP

06

BC

07

DIV

08

READ

09

PRINT

10