System Software Unit 1

1. 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.

2. 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. 

3. 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.

4. 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

5. Write the sequence of instructions to perform the operation BETA = ALPHA+5 using SIC/XE instructions.

LDA          ALPHA 

ADD          #1 

STA         BETA 

…. …. 

ALPHA      RESW       1

 BETA       RESW   1

6. 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.

7. Give the instruction set of SIC / XE.

 Load and store instruction 

Arithmetic instruction 

Register Move

Floating point arithmetic operations 

Supervisor call instruction 

Conditional jump 

Subroutine linkages

 8. Give the instruction set of SIC.

 Load and store instruction

 Arithmetic instruction 

Conditional jump instruction 

Subroutine linkages

9. What are the various data formats of SIC. 

Integers – 24 bits

Negative no. - 2‟s complement form 

Characters - 8 bits ASCII code

10. What is the format of floating pt data type in SIC/XE? 

S   exponent   fraction

1    11            36

11. What are the various data formats of SIC / XE? 

Integers – 24 bits 

Negative no. - 2‟s complement form 

Characters - 8 bits ASCII code 

Floating point - 48 bits.