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.

System Software - Unit 1

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 without 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.