Low Level Machine Code: Translation Programs

Definition: Translation

The processor's own language made up of binary numbers (0's and 1's only)

If computers can only understand a language of 0's and 1's then there is a problem of

• how can we get computers to understand letters typed in and;
• numbers larger than 1, for example 9, 112 or 2,156

 

Representing Text

Text or characters are stored in binary code. - characters include all the symbols shown on the keyboard such as numbers (0 - 9), text symbols (A - Z and a - z) and punctuation symbols(e.g, ?, :, !) and others (e.g @, £, $, &, * etc)

ASCII (American Standard Code for Information Interchange) is the most common code used to represent text. It uses a series of 8 bits 0's or 1's (or a byte) to code each character.

 

Some examples of ASCII code
Character	Binary Code
Space	0010 0000
!	0010 0001
A	0100 0001
Z	0101 1010

 

Representing Numbers

Like text, numbers are represented in Binary Code. Computers solve the problem of creating numbers larger than 1 by counting using the Binary System. - we count using the Decimal System.

The advantage of the Binary Counting System, is that it goes up in two's, rather than 10's, and this matches the two states of 1 and 0. Consider the table below where place values go up in two's.

Place values	128	64	32	16	8	4	2	1
Bits						1	0	1	= 5
Here the bits indicate that there is (1* 4) + (0*2 ) + (1 * 1). Adding all these together results in 5. From using other bits to represent place holder values other numbers can be created in binary code. For example
Example 1	0	1	0	0	1	1	0	1	= 77
Example 2	0	0	0	1	1	1	1	1	= 31
Example 3	0	0	0	0	0	0	0	0	= 0
What is the largest number that be created with 8 bits i.e coded by a single Byte (8 bits)?

 

Storage: Bits Bytes etc

In order of size
Smallest	bit	1 or 0
	byte	8 Bits e.g. 0101 1010 which represents the letter Z
	Kilobyte (Kb)	1024 Bytes
	Megabyte (Mb)	1024 Kilobytes
	Gigabyte (Gb)	1024 Megabytes
Largest	Terabyte (Tb)	Guess how many Gigabytes?
Main memory and Backing Storage of computers is measured in Megabytes (Mb) or nowadays Gigabytes. And computers with backing storage measured in Terabytes (Tb) are becoming available.

 

Representing Graphics

Graphics or pictures on computer monitors (screens) are represented by PIXELS (picture elements) Each pixel may be' on' (represented in binary by 1) or 'off' (represented in binary by 0).

 

Because each pixel in the graphic is represented by a bit (1 or 0) these pictures are called bit mapped graphics.

The more pixels there are, the better the quality of the picture.

 

 

 

 

 

 

 

 

Calculating the storage requirements of bit mapped graphics

	Steps
	Work out the total number of pixels (width * height). This gives the total number of bits. Divide the total by 8 to get the total number of bytes. Divide the total number of bytes (from step 2) by 1024 to get the file size in number of Kilobytes (Kb) Divide the total number of Kilobytes by 1024 to get the file size in Megabytes (Mb)

 

IPO Cycle
Data is processed in sequence.
Input : Programs and data files have to be 'loaded' into the processor. Processed: Something done to the data by the program according to instructions you give. Output of the results of the processing.
Processor Structure
Processor's or the brain of the computer is split into three parts.
Control Unit: Controls the operation of the processor and makes sure the program instructions are carried out in the right order. ALU (Algorithmic and Logic Unit) Does the sums and makes decisions e.g If, Then etc. Registers. Memory locations where the programmes and data are stored while being processed.

 

 

 

What you should be able to do!

1. Describe binary code.

2. Explain that text is represented by ASCII code.

3. Understand how numbers are represented. in the computer system.

4. Give in order of size bits, bytes, kilobyte, Megabyte, Gigabyte and Terabyte..

5. Explain how graphics are represented in computers.

6. Calculate the storage requirements of simple Black & White Images..

7. Explain the IPO cycle and the structure of the processor.