ICT (Computer Studies): Computer Data Conversion (1)

Data conversion is the conversion of computer data from one format another

COMPUTER DATA CONVERSION 

REGISTERS

Registers are temporary storage area for instructions or data. They are not a part of memory; rather they are special additional storage locations that offer the advantage of speed. It works under the direction of the control unit to accept, hold, and transfer instructions or data and perform arithmetic or logical comparisons at high speed. Most operations are done on the register; the processor can’t directly perform arithmetic in memory. For example, if you want to add 1 to a memory address, the processor will normally do this by loading the initial value from memory into a register, adding 1 to the register, and then saving the value back to memory.

The width (in bits) of the processor’s register determines how much data it can compute with at a time. This is sometimes used to label the processor’s size.

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 retrieve it. In modern byte – addressable computers, each address identifies a single byte of storage; data too large to be stored in a single byte may reside in multiple bytes occupying a sequence of consecutive addresses. Some microprocessors were designed to be word – addressable, so that the addressable storage unit was larger than a byte. The efficiency of addressing of memory depends on the size of the address bus.

In a computer program, an absolute address, (sometimes called an explicit address or specific address), is a memory address that uniquely identifies a location in memory. This is different from a relative address, which is not unique and specifies a location only in relation to somewhere else (the base address). Virtual memory also adds a level of indirection. Very often, when referring to the word size of a modern computer, one is also describing the size of virtual memory addresses of that computer. For example, a computer said to be “32 bits” usually treats memory addresses as 32 – bit integers; a byte addressable 32 – bit computer can address 2³² = 4,294,967,296 bytes of memory or 4 gigabyte.

BUS

A bus, in computing is a set of physical connections (cables, printed circuits etc.) which can be shared by multiple hardware components in order to communicate with one another. The purpose of bus is to reduce the number of pathways needed for communication between the components, by carrying out all communications over a single data channel.

CHARACTERISTICS OF BUS

A bus is characterised by the amount of information that can be transmitted at once.

Width is used to refer to the number of bits that a bus can transmit at once.

Frequency is the speed of the bus, which is the number of data packets sent or received per second. It is expressed in Hertz (Hz).

Cycle is refers to each time that data is sent or received.

Transfer speed is the amount of data which it can transport per unit of time. It is the product of width and frequency.

BUS SUB-ASSEMBLY

Each bus is generally constituted of 50 to 100 physical lines, divided into three sub-assemblies which are:

(i)                 Address bus (sometimes called memory bus) transports memory addresses which the processor wants to access in order to read or write data. It is unidirectional bus.

(ii)               Data bus transfers instructions coming from or going to the processor. It is bidirectional bus.

(iii)             Control bus (or command bus) transports orders and synchronisation signals coming from the control unit and traveling to all other hardware components. It is bidirectional bus, as it also transmits response signals from the hardware.

PRIMARY BUS

There are two buses within a computer;

Internal bus (also known as front – side bus (FSB)) allows the processor to communicate with the system’s central memory (RAM).

Expansion bus (also known as input/output bus) allows various motherboard components 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.

Exercises:

1.      What is data conversion?

2.      What is a register?

3.      What is a bus?

4.      What determines how much data a processor can compute at a time?

5.      What is a cycle?

6.      What is transfer speed?

7.      What does a bus consist of?

8.      What does the control bus do?

9.      What are the names of the two buses within a computer?