Computer Architecture CA134 First Unit-1 Important 2 marks Question and Answer

1. What are the elements of computers?
The computer consists of
i) Main memory
ii) Central processing unit (CPU)
iii) Program control unit
iv) Arithmetic - logic unit (ALU).
2. What is "Arithmetic logic unit (ALU)?
Arithmetic - logic unit, (ALU), which is part of the CPU's data processing or execution unit, carries out the instructions. ALU is so called because many instructions specify either arithmetic operations or various forms of non numerical operations that loosely correspond to logical reasoning or
3. What is a program?
A program is a set of instructions that specify the operations, operands and the sequence by which processing has to occur
4. What is a computer instruction?
A computer instruction is a binary code that specifies a sequence of micro; operations for the computer.
5. What is an instruction code?
An instruction code is a group of bits that instruct the computer to perform a specific operation.
6. What is an operation code?
The operation code of ah instruction is a group of bits that define operations as add, subtract, multiply, shift, and complement.
7. Define the effective address (EA)
The effective address is the address of the operand in a computation instruction or tie, target, address in a branch - type instruction.
8. What is a stack?
A stack is a storage device that stores information in such a manner that the item stored last is the first item retrieved, .It is also called as Last - In, First
out (LIFO) list.
9. What is a stack pointer?
The register that holds the address for the stack fs called stack pointer (SP) because its value always points at the top item in the stack.
10. What are the operations of a stack?
The two operations of a stack are
i) Insertion of items ii) Deletion of items
11. What is push and pop? ,
The operation of insertion is called push because it can be thought of as the result of pushing a new item on top.
The operation of deletion is called pop because ft can be thought of as the -result of removing one item so that the stack pops up.
12. What are the types of stack?
Stack can be of two types. These are
1. Register stack 2. Memory stack
13. What is the polish notation?
The polish mathematician Lukasiewicz showed that arithmetic expressions can be represented in prefix notation. This representation often referred to as polish notation, places the operator before the operands.
14. What is the reverse polish notation (RPN)?
The postfix notation, referred to as reverse polish no the operator after the operands.
15. What is an instruction format?
The format of an instruction is usually depicted in a symbolizing the bits of the instruction as they appear in memo control register. The bits of the instruction are divided into groups called fields
16. What are the fields of an instruction format?
The most common fields found in instruction formats are
1. An operation code field that specifies the operation to be performed.
2. An address field that designates, a memory address or register.
3. A mode field that specifies the way the operand or the effective address is determined.

17. What is a register address?
A register address is a binary number of kbits that defines one of 2k registers
in the CPU

18) What are the types of CPU organizations?
Three types of CPU organizations are:
1. Single accumulator organization.
2. General register organization.
3. Stack organization.
19) What is an addressing mode?
The addressing mode specifies a rule for interpreting or modifying the address field of the instruction before the operand is actually referenced.
20) What is the use of addressing modes in computers?
Computers us addressing mode techniques for the purpose of accommodating one or both of the following provision.
1. To give programming versatility to the user by providing such facilities as pointers to memory, counters for loop control, indexing of data and program relocation.
2. To reduce the number of bits in the addressing field of the instruction.

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