Systems
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Two main types of translators
Compiler Interpreter
Compiler
A compiler translates a complete high level program by converting every instruction into machine code before it executes the program.
Interpreters
An interpreter translates a high level language program one line at a time then performs the high level command. This is repeated until the whole program has been interpreted.
Compiler Advantages
• Only translate once • Immediately available for use • Runs faster than interpreted programs • Can be loaded and executed on other computers which do not have the translator programs
Compiler Disadvantages
• Program errors are only detected when the program is compiled • Development of programs is awkward as the whole program has to be compiled before it can be run
Interpreter Advantages
It error checks each line of a program as it is written which is useful for people learning to program
Interpreter Disadvantages
• The program has to be translated every time it is executed - Runs slower than compiled programs
How many bits are in a byte?
8
01100110
102
67
01000011
What is the Mantissa of 0.75843 x 10³
75843
What is the exponent of 0.75843 x 10³
3
How are real numbers stored
Floating point representation - Mantissa and Exponent
How is text stored in the computer?
ASCII 8 bits Each character has its own 8 bit number
What does ASCII stand for?
American Standard Code for Information Interchange
Vector Graphic Shapes
• Rectangle • Ellipse • Line • Polygon
Vector Graphics Attributes
x/y co-ordinates Fill colour Line colour
Vector Graphics Advantages
• Do not lose quality when scaled • Require less storage space • Objects are easily moved/manipulated • Resolution independent
Bitmap Graphics Advantages
• Can be manipulated at pixel level • Can create a wide array of graphic effects • Can represent photo-realistic images
Bitmap Graphics Disadvantages
• Requires large storage space - Image becomes jagged when scaled
The two types of main memory
RAM (random access memory) ROM (read only memory)
RAM
Random Access Memory The computers short term memory It’s volatile - when power is lost, contents of RAM are also lost
ROM
Read only memory Always retain it’s memory even when power is lost Used by mobile phones to store operating systems
Backing Storage
Used to store permanent copies of our files Examples: Hard Disk Drives, USB Flash Drives, Magnetic Tapes, CD/DVD