16. What is assembler?

Ans: The assembler translates the assembly language program text which is given as input to the assembler to their binary equivalents known as object code. The time required to translate the assembly code to object code is called access time. The assembler checks for syntax errors & displays them before giving the object code.

17. What is loader?

Ans:The loader copies the program into the computer’s main memory at load time and begins the program execution at execution time.

18. What is linker?

A linker is a program used to join together several object files into one large object file. For large programs it is more efficient to divide the large program modules into smaller modules. Each module is individually written, tested & debugged. When all the modules work they are linked together to form a large functioning program.

19. Explain ALIGN & ASSUME:

Ans: The ALIGN directive forces the assembler to align the next segment at an address divisible by specified divisor. The format is ALIGN number where number can be 2, 4, 8 or 16. Example ALIGN 8.
The ASSUME directive assigns a logical segment to a physical segment at any given time. It tells the assembler what address will be in the segment registers at execution time. Example ASSUME CS: code, DS: data, SS: stack

20. Explain PTR & GROUP

Ans: A program may contain several segments of the same type. The GROUP directive collects them under a single name so they can reside in a single segment, usually a data segment. The format is Name GROUP Seg-name,…..Seg-name PTR is used to assign a specific type to a variable or a label. It is also used to override the declared type of a variable.

21. What are the three classifications of 8086 interrupts?

Ans:

(1) Predefined interrupts
(2) User defined Hardware interrupts
(3) User defined software interrupts.

22. What are the functions of status pins in 8086?

Ans:

S5 --Status of interrupt enable flag
S6 --Hold acknowledge for system bus
S7 --Address transfer.

23. What are the schemes for establishing priority in order to resolve bus arbitration problem?

Ans: There are three basic bus access control and arbitration schemes

1. Daisy Chaining
2. Independent Request
3. Polling

24.What are the different types of methods used for data transmission?

Ans: The data transmission between two points involves unidirectional or bi-directional transmission of meaningful digital data through a medium. There are basically there modes of data transmission.

(a) Simplex
(b) Duplex
(c) Half Duplex

In simplex mode, data is transmitted only in one direction over a single communication channel.For example, a computer (CPU) may transmit data for a CRT display unit in this mode.
In duplex mode, data may be transferred between two transreceivers in both directions simultaneously.
In half duplex mode, on the other hand, data transmission may take pace in either direction, but at a time data may be transmitted only in one direction. For example, a computer may communicate with a terminal in this mode. When the terminal sends data (i.e. terminal is sender). The message is received by the computer (i.e the computer is receiver). However, it is not possible to transmit data from the computer to terminal and from terminal to the computer simultaneously.

25.What are the various programmed data transfer methods?

Ans:

i) Synchronous data transfer
ii) Asynchronous data transfer
iii) Interrupt driven data transfer

26. What is synchronous data transfer?

Ans: It is a data method which is used when the I/O device and the microprocessor match in speed. To transfer a data to or from the device, the user program issues a suitable instruction addressing the device. The data transfer is completed at the end of the execution of this instruction.

27. What is asynchronous data transfer?

Ans: It is a data transfer method which is used when the speed of an I/O device does not match with the speed of the microprocessor. Asynchronous data transfer is also called as Handshaking.

28.What are the different inter connection topologies?

Ans:

• Shared bus
• Multiport Memory
• Linked Input/Output
• Bus window
• Crossbar Switching.

29. What are the configurations used for physical interconnections?

Ans:

• Star Configuration
• Loop configuration
• Complete interconnection
• Regular topologies
• Irregular topologies

30. Give the instruction set of 8087?

Ans:

1. Data Transfer Instructions
2. Arithmetic Instructions
3. Comparison Instructions.
4. Transcendental Operations.
5. Constant Operations.
6. Coprocessor Control Operations.

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