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
