Computer Data Conversion

Definition of Terms

Data Conversion

Data conversion is the transformation of computer data from one format to another.

Registers

Registers are temporary storage areas for instruction or data.
It can also be defined as a special, high-speed storage area within the CPU.
Registers are not part of the memory; but rather, they are additional storage locations that offer the advantage of speed. Register works under the direction of the control unit to accept, hold and transfer instruction or data and perform arithmetic or logical comparison at high speed. Registers are the fastest memory available for use in the PC because they are hard-wired right into the processor logic.

Address

A memory address is an identifier for a memory location at which a computer program or a hardware device can store data and later receive it.

Bus

A bus is a set of physical connections (cables, printed circuits, etc.) which can be shared by multiple hardware components to communicate with one another. The purpose of buses is to reduce the number of "pathways" needed for communication between components, by carrying out all communications over a single data channel. This is why the metaphor of a "data highway" is sometimes used. If only two hardware components communicate over the line, it is called a hardware port (such as a serial port or parallel port).

A bus is characterized by the amount of information that can be transmitted at once. This amount, expressed in bits, corresponds to the number of physical lines over which data are sent simultaneously. A 32-wire ribbon cable can transmit 32 bits in parallel. The term, "width" refers to the number of bits a bus can transmit at once. In addition, the bus speed is also defined by its frequency (expressed in Hertz), the number of data packets sent or received per second. Each time that data is sent or received is called a cycle. This way, it is possible to find the maximum transfer speed of the bus, the amount of data which it can transport per unit of time, by multiplying its width by its frequency.

Example: What is the speed of a bus with a width of 16 bits and a frequency of 133 MHz?
Solution

Types of Computer Buses

Internal Bus: The internal bus (sometimes called the front-side bus, or FSB for short). The internal bus allows the processor to communicate with the system's central memory (the RAM).
Expansion Bus: The expansion bus (sometimes called the input/output bus) allows various motherboard components (USB, serial, and parallel ports, cards inserted in PCI connectors, hard drives, CD-ROM and CD-RW drives, etc.) to communicate with one another. However, it is mainly used to add new devices using what are called expansion slots connected to the input/output
Address bus: carries memory addresses from the processor to other components such as primary storage and input/output devices. The address bus is unidirectional, that is, data only move in one direction.
Data bus: carries the data between the processor and other components. The data bus is bidirectional, that is, data can move in two directions (to and fro simultaneously)
Control bus: carries control signals from the processor to other components. The control bus also carries the clock's pulses. The control bus is unidirectional, that is, data only move in one direction.

Types of Register and their Functions

There are many types of registers; some of them are examined below:
Memory Data Register (MDR): This register contains the data to be stored in the computer storage or the data after a fetch from the computer storage.
Current Instruction Register (CIR): CIR stores the instruction currently being executed or decoded.
Memory Address Register (MAR): MAR holds the memory address of data and instruction.
Program Counter (PC): PC is commonly called instruction pointer (IP) and sometimes called instruction address register. It is a register that holds the address of the memory location of the next instruction when the current instruction is executed by the microprocessor.
Accumulator Register: This register is used for storing the results that are produced by the system.

Functions of Registers

Functions of the registers are:
i.Registers hold the address of memory where the CPU wants to read or write data
ii. They hold the contents of data instruction read from or written in memory
iii.They are used to specify the address of a particular I/O device
iv. Registers are used for exchanging data between the I/O module and the processor
v. They store current instructions being executed or coded
vi. Registers allow the bits of its content to be moved to left or right (shift register)
vii.They hold the memory addresses of data and instructions during the execution phase
viii. Registers store the result produced by the system

Differences between Registers and Main Memory

Register	Main Memory
Registers are located inside the processor	Main memory is located outside the processor
They are very fast	They are slow
They are small in capacity	They are large in capacity

Fetch-Execute Cycle

The fetch-execute cycle is the sequence the computer follows to transform data from one format to another.
The steps in the processing cycle are as follows:
Fetch the next instruction: The program counter contains the address of the next instruction to be executed; the control unit goes to the address in the memory specified in the program counter, makes a copy of the contents and places the copy in the instruction register.
Decode the Instruction: To execute the instruction in the instruction register, the control unit has to determine what the instruction is.
Get Data If Needed: It may be that the instruction to be executed requires additional memory accesses to complete its task. If this is the case, the control unit must get the content of the memory location.
Execute the Instruction: Once an instruction has been decoded and any data fetched, the control unit is ready to execute the instruction. Execution involves sending signals to the arithmetic/logic unit to carry out the processing. When the execution is complete, the cycle begins again.

Fetch-Execute Cycle Flow Diagram

Factors Affecting the Speed of Data Transfer

i. The amount of RAM: The larger the size of the computer RAM the faster the speed of data transfer and vice versa.
ii. The speed and generation of your CPU (the system clock): The speed of the computer is measured in Hertz (Hz) which is the number of tasks it can process per second. A computer with a specification 2GHz can process 2 billion tasks in one second. This implies that the faster the speed of the computer the faster the speed of data transfer.
iii. The size of the Register on your CPU: The speed of data transfer will be faster if the size of the register is also large and vice versa.
iv. The Bus width: The larger the width of a bus, the faster the number of bits that bus can transmit at once.
v. The Bus speed: High bus speed will favour faster speed of data transfers
vi. The amount of Cache memory: Cache memory is a temporary memory that holds frequently accessed data and instructions for faster and more efficient processing by the CPU. The higher the size of cache memory the faster the speed of data transfer. The downside of the cache memory is that it trades off capacity for speed.