(SS) System Software Viva Question and Answers
VIVA VOCE QUESTIONS WITH ANSWERS INTRODUCTION
1. Define system software.
It consists of variety of programs that supports the operation of the
computer. This software makes it possible for the user to focus on the
other problems to be solved with out needing to know how the machine works
internally.
Eg: operating system, assembler, loader.
2. Give some applications of operating system.
• to make the computer easier to use
• to manage the resources in computer
• process management
• data and memory management
• to provide security to the user.
Operating system acts as an interface between the user and the system
Eg:windows,linux,unix,dos
3. Define compiler and interpreter.
Compiler is a set of program which converts the whole high level
language program to machine language program. Interpreter is a set of
programs which converts high level language program to machine
language program line by line.
4. Define loader.
Loader is a set of program that loads the machine language translated by
the translator into the main memory and makes it ready for execution.
5. What is the need of MAR register?
MAR (memory address register) is used to store the address of the
memory from which the data is to be read or to which the data is to be
written.
6. Draw SS instruction format.
opcode L B1 D1 B2 D2
0 7 8 15 16 19 20 31 32 35 36 47
It is a 6 byte instruction used to move L+I bytes data fro the storage
location1 to the storage location2.
Storage location1 = D1+[B1]
Storage location2 = D2+[B2]
Eg: MOV 60,400(3),500(4)
7. Give any two differences between base relative addressing and program
counter
relative addressing used in SIC/XE.
8. Define indirect addressing
In the case of immediate addressing the operand field gives the memory
location. The word from the given address is fetched and it gives the
address of the operand.
Eg:ADD R5, [600]
Here the second operand is given in indirect addressing mode. First the
word in memory location 600 is fetched and which will give the address of the
operand.
9. Define immediate addressing.
In this addressing mode the operand value is given directly. There is no
need to refer memory. The immediate addressing is indicated by the prefix ‘#’.
Eg: ADD #5
In this instruction one operand is in accumulator and the second operand is
an immediate value the value 5 is directly added with the accumulator content
and the result is stored in accumulator.
10. List out any two CISC and RISC machine.
CISC –Power PC, Cray T3E
RISC – VAX,Pentium Pro architecture
11. Following is a memory configuration:
Address Value Register R
1 5 5
5 7
6 5
What is the result of the following statement?
Base relative addressing PC relative addressing Here the Target address is
calculated using the formula
Target address = Displacement + [B] B-base register
Here the target address is calculated using the formula Target address =
Displacement + [PC]
PC-program counter
Displacement lies between 0 to 4095 Displacement lies between –2048 to
2047
21
ADD 6(immediate) to R (indirect)
Here 6 is the immediate data and the next value is indirect data. ie, the
register contains the address of the operand. Here the address of the operand
is 5 and its corresponding value is 7.
6 + [R] = 6+ [5] = 6+ 7 =13
12. Following is a memory configuration:
Address Value Register R
4 9 6
5 7
6 2
What is the result of the following statement?
SUB 4(direct) to R (direct)
Here one operand is in the address location 4(direct addressing) and the
next operand is in the register (register direct).
The resultant value is 9 –6 =3.
13. What is the name of A and L register in SIC machine and also specify
its use.
A-accumulator
Used for arithmetic operation. i.e., in the case of arithmetic operations
one operand is in the accumulator, and other operand may be an immediate value,
register operand or memory content. The operation given in the instruction is
performed and the result is stored in the accumulator register.
L-linkage register
It is used to store the return address in the case of jump to subroutine
(JSUB) instructions.
14. What are the instruction formats used in SIC/XE architecture? Give any
one format.
Format 1 (1 byte), Format 2 (2 bytes), Format 3 (3 bytes) & Format 4(4
bytes)
Format 2:
8 4 4
OPCODE R1 R2
15. Consider the instructions in SIC/ XE programming
10 1000 LENGTH RESW 4
22
20 ----- NEW WORD 3
What is the value assign to the symbol NEW?
In the line 10 the address is 1000 and the instruction is RESW 4.It
reserves 4 word (3 x 4 =12) areas for the symbol LENGTH. hence 12 is added
to the LOCCTR. Thus the value of the symbol NEW is 1000+12 =100C.
16. What is the difference between the instructions LDA # 3 and LDA THREE?
In the first instruction immediate addressing is used. Here the value 3 is
directly loaded into the accumulator register. In the second instruction the
memory reference is used. Here the address(address
assigned for the symbol THREE) is loaded into the accumulator register.
17. Differentiate trailing numeric and leading separate numeric.
The numeric format is used to represent numeric values with one digit per
byte. In the numeric format if the sign appears in the last byte it is known as
the trailing numeric. If the sign appears in a separate byte preceding the
first digit then it is called as leading separate
numeric.
18. What are the addressing modes used in VAX architecture?
Register direct; register deferred, auto increment and decrement,
program counter relative, base relative, index register mode and indirect
addressing are the various addressing modes in VAX architecture.
19. How do you calculate the actual address in the case of register
indirect with immediate index mode?
Here the target address is calculated using the formula
T.A =(register) + displacement.
20. Write the sequence of instructions to perform the operation BETA =
ALPHA + 1 using SIC instructions.
LDA ALPHA
ADD ONE
STA BETA
…. ….
ALPHA RESW 1
BETA RESW 1
ONE RESW 1
21. Write the sequence of instructions to perform the operation
BETA = ALPHA+5
using SIC/XE instructions.
23
LDA ALPHA
ADD #1
STA BETA
…. ….
ALPHA RESW 1
BETA RESW 1
22. What is the use of TD instruction in SIC architecture?
The test device (TD) instruction tests whether the addressed device is
ready to send or receive a byte of data. The condition code is set to
indicate the result of this test. Setting of < means the device is ready to
send or receive, and = means the device is not ready.
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