Computer technology The history of computer technology video clip The history of computer technology video clip The history of computer technology video.

Computer technologyComputer technology

The history of computer technology The history of computer technology video clipvideo clip

Low Level MachineLow Level Machine

how a computer handles the smallest amounts of data in its

processor.


how data is represented inside the computer.


INPUT

PROCESS

OUTPUT


INPUT the entering of the data.

PROCESS the calculation is done

OUTPUT

Random Access Memory stores the data

by the central processing unit and the answeris the


The CPU consists of three parts:

Memory to store small amounts of instructions

Arithmetic Logic Unitto do the calculations

Control Unit controlling the input and outputsof the CPU


The CPU

Memory

ALUControl Unit

Input line from keyboard

Watch a video clip

Low Level MachineLow Level MachineThe CPU

Memory

Arithmetic and Logic Unit

Control Unit

RAM


01010110 101010b1 01010101 010111000 10101110 1001i111 11010101000010101 11111000 1n110000 110100101 10010101 1011011a 00111010101010101 011011101 010r0101 01110101 01011101 11000111 1y100010

bin

ar

y


Binary is also known as machine code, as it’s the code which instructs the machine

Every 0 or 1 is called a binary digit or bit

Eight bits represent a character for example,0100 0001 represents the letter A

Eight bits together are called a byte

We use the byte to measure capacity of a computersfor example, kilobyte, megabyte and gigabyte.


Eight bits = 1 byte

1 kilobyte = 1024 bytes and is written as 1kb

1 megabyte = 1024*1024 kilobytes or= 1 048 576 bytes written as 1mb

1 gigabyte = 1024 * 1024 * 1024 kilobytes= 1 073 741 824 bytes or 1gb


If the computer has to process data it must store it

All data is stored in the computers memory

The memory of the computer is measured in bytes

Each memory location can hold one byte of data (or a multiple of bytes)

Each memory location has an unique address

This way of identifying each memory location is called addressability

Low Level MachineLow Level Machine0101001111011011

memory locations

11011011110110111101101111011011110110111101101111011011110110111101101111011011

Each memory locationwill have its own unique address

0000000100000010000000110000010000000101000001100000011100001000000010010000101000001011000011000000110100001111

memory addressesOne byte

Low Level MachineLow Level MachineData travels from input devices to the processor, or between RAM and the processor or to and fromthe different parts of the processor in groups of bits

This group is called a WORD

Older computers had a WORD LENGTH of 2 bits thisincreased to 4 and then 8 now most modern PC’s havea WORD LENGTH of 16, 32 or 64 bits

This means that data is passed around much fasterand tasks carried more quickly


A 2 bit machine would transfer the data 2 bits at a timeThis would mean time for a total of 16 transfers

A 8 bit machine would need only time for 4 transfers

A 16 bit machine would need only time for 2 transfers

A 32 bit machine would need only time for 1 transfer

The data to be processed 01011100 1010110001011100 10101100


Doing a simple calculation (and not accurately reflecting)

The 2 bit machine is 16 times slower than the 32 bit machine

The data being processed will take 4 minutes on the 2 bit machine

and only 15 seconds on a 32 bit


Each character that appears on the keyboard has a specialcode to represent it consisting of 1s and 0s these are knownas alphanumeric characters

Each country and language has a special collection of characters and so a collection of characters is known as acharacter set

Computer manufactures have had to standardise on thebinary code that they have allocated to each character andthe most popular one is the ASCII set


A American

S Standard

C Code

I Information

I Interchange

ASCII allows different Computer systems to communicate with each other because text is represented by the same code

Low Level MachineLow Level MachineControl Characters control certain operations the computer carries out

For example ctrl-p will tell the operating system to print the current screen

Other codes may tell the computer to print condensed ortake a new line – the return key

Control Characters are also represented by ASCII

ASCII uses 7 bits and therefore one character set can have up to 127 individual characters

computing

the MSB the eighth bit is 0 and is not used to distinguish ASCCII code characters

Low Level MachineLow Level MachineGraphics on the screen are made up of tiny dots called pixels

The more pixels on the screen the better the picture

The more pixels – the higher the resolution and the more memory needed to store each pixel

In a black and white picture all black pixels would be stored as a 1 and all white pixels as a 0

So high resolution screens and graphics need morememory than low resolution ones


If we increase the size of this graphic we will begin to see the pixels

Click here to see the graphic at 1000%


0 0 0 0 0 0 0 0 0 0 00 0 0 1 1 1 1 1 0 0 00 0 1 0 0 0 0 0 1 0 0

Black pixels are represented by a 1 and white pixels by a 0

Low Level MachineLow Level MachineBinary can represent any number whole and real

The binary number system is a base 2 systemDecimal is a base 10 system

128 64 32 16 8 4 2 1

0 0 0 0 0 1 0 1 =50 1 0 1 1 0 1 0

=901 1 1 1 1 1 1 1

=2550 1 0 1 1 0 0 0 =

88

Low Level MachineLow Level MachineUsing binary to represent non negative integers is very straightforward

Of course numbers larger than 255 will require more than 1 byte to represent them

4 bytes can be used to represent a number this gives the

binary number 232 or thirty two 1s

11111111 11111111 11111111 11111111

This is 4,294,967,295 although the top of the range is about half of this to allow for negative numbers

Low Level MachineLow Level MachineBut what happens when the number is bigger than 2000 million?

The computer uses Floating Point Representation also known as standard form or scientific notation

FPR is also used to represent real numbers i.e. numbersthat are not whole numbers e.g. 51.6784, very small andand very large numbers.

In decimal 60 420 000 000 can be represented as

6.042*1010


Sign (+ or -) positive numbers are not signed

Decimal FPR has four components:

Exponent (10)

Mantissa (6.042) Base (10)

6.042*1010


The sign indicates whether the number is positive ornegative

The exponent indicates how many places the point hasbeen moved

The base indicates the number system being used

The mantissa indicates how many places the point has been floated


In binary the position of the point is always the same

The number base is always two

All that is needed to be stored is the mantissa and theexponent

28.5 = 11100.0101=0.111000101 * 0101

Decimal Binary FPR

111000101 0101

Mantissa Exponent

Low Level MachineLow Level MachineReturn to picture at 100%

The pixels are the small squares

Computer technology The history of computer technology video clip The history of computer technology video clip The history of computer technology video.

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