1.1 The characteristics of contemporary processors, input, output and storage devices

Arithmetic Logic Unit - performs arithmetic and logical operations on the data

Control Unit - controls and coordinates the activities of the CPU, directing the flow of data between the CPU and other devices

Registers

Program Counter - holds the address of the next instruction to be executed

Accumulator - the register where all the calculations take place 

Memory Address Register - holds the address of the memory location from which the data or an instruction has to be fetched or written to

Memory Data Register - temporarily stores the data read from or written to memory; acts as a buffer 

Current Instruction Register - holds the current instruction being executed divided into operand (data) and opcode (instructions)

General Purpose Register - used temporarily to store data in order to be quicker than sending it to memory

Buses 

Data Bus - typically consists of 8,16,32 or 64 separate lines providing a bi-directional path for moving data and instructions between system components.

The address bus carries the address the address of the memory location being read from or written to 

Control bus - a bi-directional bus meaning that signals can be carried in both directions. Control lines must therefore be provided to ensure that access to and use of data and address buses by the different components of the system does not lead to conflict. The purpose of the control bus is to transmit command, timing and specific status information between system components. 

How does this relate to assembly language?

The basic structure of a machine code instruction in a computer with a 16-bit word may take the format shown below:

Operation Code

Operand

Basic Machine Operation

Addressing Mode

0

1

0

0

0

1

0

1

0

0

0

0

0

0

1

1

In assembly language, the opcode will be expressed as a mnemonic such as ADD, SUB and LDA. With only six bits for the opcode  there can't be more than 64  different instructions. The operand has to be held in only 8 bits. This is not practical for a general purpose computer which is…