1.2.4 extension

Question 1

What is the opcode?

Answer 1

Consists of binary digits representing the basic operations such as ADD and 2 digit code representing addressing mode

(Addressing mode attached to opcode)

Question 2

How do you calculate maximum number of operations for instruction set

Answer 2

2^n

Question 3

What indicates the the addressing mode?

Answer 3

Indicated by bit pattern that’s the last 2 bits of opcode

Question 4

What is immediate addressing?

Answer 4

Operand is actual value to be operated on

(Don’t need to go to memory)

Question 5

What is direct addressing?

Answer 5

Operand holds memory address of value to be operated on
Only addressing mode used in LMC assembly language

Question 6

What is indirect addressing?

Answer 6

Operand is location (typically a register) which holds address of data we want

Reference to memory location where we find real address of required data

Enables larger range of addressable locations (without we can’t hold memory addresses larger than 16 if operand only 4 bits!)

Question 7

What is indexed addressing?

Answer 7

Address of operand obtained by adding a constant value to contents of general register (called index register)

Number of index register and constant value are included in instruction code

Used to access an array whose elements are in successive memory locations

Question 8

Why does array need to be stored in contiguous memory?

Question 9

High level languages

Answer 9

3rd generation
Abstraction of machine level steps taken to solve problems
More accessible
Problem-oriented as opposed to machine orientated
One to many relationship w machine code (each instruction gives rise to many lines of machine code)

Question 10

What are imperative languages?

Answer 10

Programs written as lists of commands which describe how problem should be solved (tell comp what to do step by step)

Question 11

What is a procedural language?

Answer 11

Type of imperative Lang that are structured using procedures/subroutines/functions

Program where instructions given in sequence, selection used to decide what program does, iteration dictates how many times it does it
Programs broken down into key blocks called ‘procedures, functions’

Examples - BASIC, C, Pascal

Question 12

What is a declarative language?

Answer 12

Describe problem to be solved or what program should achieve rather than how to solve it

Eg SQL

Question 13

What is procedural programming

Answer 13

Type of imperative programming paradigm where program is built from 1 or more subroutines (procedures, functions etc)