Computer Systems Flashcards
Binary
All the circuits in a computer are based on two-states
The states are ON (1) and OFF (0)
These states are represented by voltages on llines inside a computer
Two states are easy and econimic to produce
Arithmetic rules are simpler in using 0 and 1
The patterns of 0 and 1 are called binary
Units in Binary
0 ir 1 = 1 bit (binary digit) 8 bits = 1 byte 1024 bytes = 1 kibiyte (kb) 1024 kibibytes = 1 mebibyte (mb) 1024 mebibytes = 1 gibibyte (gb) 1024 gibibytes = 1 tebibyte (tb) ect...
Decimal to Binary
There are 2 ways that we can turn a decimal into a binary number
We can write down our culumn headings and work it out from there
Or we can keep dividing the number by 2, writing down the remainder until we are at 0
Floating-Point Representation
In order to store very large, very small and decimal (real) numbers (1,2, ,ect), they are stored as floating point numbers
A floating point number is made of two parts called the Mantissa and Expoent
E.g.
3x10^8
3 = mantissa
8 = exponent
This is how to represent the number 300000000
Floating-Point Representation (more)
If you want to store really percise decimal numbers, ie lots of numbers after the decimal place, then you need to have a large mantissa
If you want to store large numbers then you need to have a large exponent
Storing Text
To store text in a computer we give each character its own special number
This number is called its code
We can then store this code in the computer using binary
There are many systems in place for storing text but for National 5 we will concentrate on Extended ASCII
Extended ASCII
Extended ASCII uses 9 bits to store each letter, number or symbol
Each letter, numebr or symbol is given a number code from 0 to 255
E.g. Captial A = 65 (binary 01000001)
The number of characters that can be stored in Extended ASCII is 256 (2^8)
There are 32 control characters
Control characters are keys on the keyboard taht are non-printable and dont appear on your screen
Bit-Mapped Graphics
A bit=mapped image stores every pixel that makes up an image, even if it has no data
Resolution - number of pixels in width and height
The number of bits used to represent each pixel is called the bit-depth or colour depth
The numebr of bits will vary depending on the number of colours that can be represented
Bit-Mapped Graphics
Advantages and Disadvantages
Advantages:
- Image can be manipulated at pixel level
- A wider range of shapes can be produced
Disadvantages:
- Requires large amounts of storage
- Image can become jagged when scaled
Vector Graphics
Vector graphics stores the attributes of the objects which make up the image
E.g. line length, line colour, line thickness, starting coordinate
They are resolution independent, which means that they do not lose quality when they are scales up and down
Vector Graphics
Advantages and Disadvantages
Advantages:
- No loss of quality during resizing
- Less storage space required
- Can be edited at object level
- Objects can be grouped
Disadvantages:
- Not so many options (free drawing)
- Cannot be edited in detail
Processor
The processor is the part of the computer system that handels the instruction used to ensure hardware and software responds to the user as expected
Processors can handle millions of instructuins per second
The processor is made up of 3 parts:
-The Control Unit
-The Arithmetic Logic Unit (ALU)
-Registers
Registers
Tempprary storage locations
Stores locations to access - addresses
Stores data it needs to write to memory
Stores the results of calculations
ALU
Performs all the calculations
Makes decisions based on logic
AND, OR, NOT, >,
Control Unit
The control unit controls the flow of data within a computer system
It controls and monitors communications between the hardware attached to the computer
It controls:
-the input and output of data
-checks that signals have been delivered successfully
-makes sure that data goes ti tge correct place at the correct time
Main Memory (RAM)
When a program is running, the data that will be processed by the processor is temporarily stored in RAM
RAM will hold data until it is needed by the processor
When a program is closed the data held in RAM is deleted
When the computer system shuts down, RAM is cleared completely as it requires power to operate
Memory Locations
There are many different locations in RAM and each location has its own unique address
The more RAM that is available, the more programs it is possible to run cocurrently withpit slowing system performance
New desktop PCs will usually have between 8Gb abd 16Gb of RAM
Buses
Buses are the sets of wires connecting the processor to the main memory and peripherals
Adderss Bus
This carries address information from the processor to main memory or peripherals
It is uni-directional (this means the address can only be transmitted from the processor to the memory)
The processor keeps track of the addresses being used by a program
Data Bus
This buss carries the actual data from the processor to the memory or peripherals
It is bi-directional (this means that it is possible to transfer data both to and from the processor and memory)
Translation
Most software is written by programmers using a high level language
High level languages make writing program code easy because they use words from the English language and mathmatical signs you are familial with
Computers only understand machine code. Machine code is made up of binary digits (1’s and 0’s)
So that a computer can carry out a program written in high level language the program must be translated into machine code
Interoreter
Translates code one line at a time
Gives accurate error messages where the error occurs
Easier to spot/edit mistakes
BUT every time code is run you must use the interpreter
Compiler
Compiles whole code in one go therefore faster than interpreter
Only needs to be compiled once and produces object code
Once compiled it doesn’t need to be translated again
Can be harder to spot/edit mistakes
Interpreter VS Compiler
An interpreter is used for program development as it is easier to debug and partially test the code
Once the program is error free and complete, the program should then be compiled, as compiling only needs to be done once
Energy Use of Computer Systems
Any company using electronic equipment must evaluate their energy use
This will save them money and also prolong the life of much of their equipment
Monitor Settings
Use energy efficient monitors
Reduce brightness on monitors during the day
Avoid the use of screensavers
Power Down Settings
Only switch peripherals on when they are needed
Switch off all machines at the end of the day or when not in use
Computers on Stand-By
Activate standby settings for Desktops
Activate standby settings for laptops
Activate standby settings on energy efficient monitors
Implications on the Environment
Creating and running computer systems requires a lot of energy
This energy comes form electricity that is mostly generated from fossil fuel
This released harmful gases and emissions that damage the atmosphere
Carbon Footprint
The amount of Carbon Dioxide used in the manufacture, use and disposal of computer equipment
Manufacturing
The materials and resources used to create and build computer systems during manyfacture
Use
Electricity usage
Replacement parts ect, as the device used in its everyday life
Disposal
Energy is used to:
- Collect
- Take apart
- Dispose
of an electronic device
