N5 – Low-level operations and computer architecture

Explanation of the need to translate high-level program code to binary (machine code).  
Computers can only understand binary code, therefore all human readable programming codes have to be translated into binary. Binary code which contains machine specific instructions is called machine code. A machine code file will only work on the computer type it was created for. Therefore one program does not work on different systems (X Box and Play Station)
Comparison of interpreters and compilers.  
Interpreters – These are resident in the computer’s memory when the program is executed. These translate the source code (program) one line at a time into machine code, this can make them appear slow. Syntax errors are often highlighted as they are made.

Compilers – These translate the source code into machine code, this machine code can then be saved and executed without further need for the compiler. Making the program appear to execute faster than the interpreted version. Syntax errors are only apparent at run time.
Description and exemplification of the use of binary to represent positive integers.  
Binary is a base 2 numbering systems where every digit can have two values ( 0 / 1 )

This is because computers can only represent information using electricity which is either on (1) or off (0)
Conversion from Binary to decimal and vice-versa.  
To convert a decimal number to a binary number, we need to start at 1 and double it.

128 64 32 16 8 4 2 1
0 0 1 0 1 0 1 0

So the number above is 42 ( 32+8+2)
Description of floating point representation of real numbers using the terms mantissa and exponent.  
Binary can only store a whole number so to store a real number we use floating point notation. MxBe. The Base is 2 for binary.

The Mantissa stores the number itself and therefore controlling the accuracy.

The Exponent store the magnitude of the number and therefore controls the range.

Mantissa Range Exponent Accuracy (MARE)
Description of ASCII code (7-bit) used to represent characters.  
American Standard Code for Information Interchange.

Every letter is given a number (A = 65) this is then stored as binary. This allows us to store 128 different symbols and commands, this allows for messages and documents to be read by different computer systems. The 1st 32 numbers are reserved for non-printing characters, such as TAB and RETURN.
Description of the vector graphics method of graphic representation.  
Vector Graphics store pictures as a series of objects and their attributes.

To draw a red circle we would need a circle object and then describe it with attributes.

<circle cx=”50″ cy=”50″ r=”40″ stroke=”black” stroke-width=”3″ fill=”red” />

This is very useful for storing non-photographic work as it can be scaled up without losing quality.
Description of the bit-mapped method of graphics representation.  
Bitmap graphics store images as a grid of pixels (Picture Elements). These pixels values can be changed to display an image. Bitmaps can require a large amount of storage, especially when using colour. The greater the number of pixels the higher the resolution therefor the larger the file size.
Describe the purpose of the Basic computer architecture components and how they are linked together including:  
processor  
The processor is the part of the computer which execute the program, controlling the hardware and software of the computer system. It is composed of three parts.

Control Unit, Arithmetic and Logic Unit, and Registers

CU, Ah Luv U, Right.
control unit  
This is the part of the processor which controls the execution of the program. It uses a clock pulse to sync all parts of the computer, measured in Hertz (Hz). This is often used to measure the speed of a computer. You would expect a 3GHz computer to be faster than a 1GHz computer.
Arithmetic and Logic Unit (ALU)  
This part of the processor performs calculation and is used to evaluate logical decisions (AND OR NOT)
registers  
This is a temporary storage area inside the processor. It is used to store instructions, memory locations or values currently in use. Resetting a processor will clear these values.
memory  
Computer memory can either be RAM or ROM.

Random Access Memory is used to store the data currently being processed, it is volatile meaning that its contents are lost when the power is turned off.

Read Only Memory is used to store programs or data that cannot be changed, such as the operating system or serial number. Contents are not lost when power is removed.
Units of storage

  • bit
  • Byte
  • KB
  • MB
  • GB
  • TB
  • PB
  

  • bit = Binary Digit (0 or 1)
  • 1 Byte = 8 bits
  • 1 KiloByte = 1024 Bytes
  • 1 MegaByte = 1024 KB
  • 1 GigaByte = 1024 MB
  • 1 TerraByte = 1024 GB
  • 1 PetaByte = 1024 TB

 

  
Data Bus  
This is used to carry data from the processor to peripherals (other parts of the computer) and vice versa. The data bus is therefore a bi-directional bus. A bus is simply a group of wires.
Address Bus  
This is used to carry the location of the data from the processor to memory and peripherals. This is a Unidirectional bus.
Interfaces  
An Interface is a hardware device that compensates for differences between the processor and peripheral devices. For example, sound data is analogue and the interface would need to change it to digital before it could be used. There are a number of common interfaces, which are disused later.

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