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Computing Revision, 2.4 Computational Logic - Coggle Diagram
Computing Revision
1.2 Memory and Storage
Sound
Sound is sampled which turns analogue waves digital for the computer to process.
Sampling rate is how quickly the computer takes samples from the sound
The more samples or the higher sample rate the closer the sound will be to real life
Images
Bitmaps images are stored as binary digits for each colour. The binary also includes metadata which shows colour depth and width and height of the image. The order of the pixels is shown in the order of binary
A 1 bit image has a chance for 2 different colours: 1,0
A 2 bit image has a chance to have 4 different colour: 00,01,10,11
A 3 bit image has a chance to have 8 different colour: 000, 100,010,001,110,011,101,111
Compression
Compression reduces the file size and this is great because you can store more data on a device
Lossy Compression: Lossy Compression loses some of the data when the file is compressed. Its used for images with small colour range and cannot be used for documents or execute code as info from this cannot be lost.
Lossless Compression: Lossless Compression does not loose any data but just encodes it differently. This type is used for text documents and execute code because the data cannot be lost. the way its encoded is by the colour then the quantity of colour.
Primary Storage
ROM
Its purpose is to store PC boot data so the computer can turn on. Its non-volatile and can only be read.
Read Only Memory
RAM
Its purpose is to temporarily store frequently/ recently used data/instructions. Its volatile and can be read or wrote to
Random Access Memory
Cache
To store the most frequently used data and instructions and is placed very close to the CPU. this is the fastest type of memory
1.1 Systems and Architecture
Central Processor unit (CPU)
The CPU contains many registers
MAR
The Memory Address Register stores the location in memory to be used by the MDR. Holds the address of where data is to be fetched or stored
Cache
This memory provides access to frequently used instructions.
CU
The Control Unit decodes instructions and sends signal to control how data moves around the CPU
ALU
The Arithmetic Logic Unit performs calculations
ACC
The Accumulator holds the result of calculations
PC
The Program Counter holds the address of the next instruction
MDR
Memory Data Register holds data fetched from or to be written to the memory
Fetch Decode Execute cycle
Decode
For the decode stage the Control Unit decodes the instruction and sends the value to the accumulator. The accumulator is where data is stored temporarily while mathematical and logical operations are performed by the Arithmetic Logic Unit. Now the Control Unit can tell the other components to execute the intructions
Execute
The control unit first updates the memory address register and retrieves more information from the memory before that data is sent back. Then it finally makes it way to the accumulator, where the number is stored, bringing the execute stage to an end.
Fetch
The Memory adress held in the Program Counter is carried by the bus to the memory address register. Then this address is sent to the memory to get data. When it finds the address, the instruction is taken by the data bus to the memory address register because its a value. The instruction is copied to the current instruction register which holds it. Then its copied to the control unit. Then the Control Unit sends out an instruction to the program counter moving the address up one digit
Vonn Neumann Architecture
The Von Neumann Architecture is special because it stores instruction data and program data in the same memory.
It is simpler than pre programs and only uses a single processor while also executing programs by doing one instruction at a time
This is done using fetch decode execute cycle which is unique to this architecture
It is based on the concept of stored-program
Embedded systems
An embedded system is a computer system with a dedicated system within a larger electrical ore electrical system
2.4 Computational Logic
Logic Gates
AND gate
This gates means you have to have both inputs on to pass a current
OR gate
This gate allows a current through if either of the inputs are on
NOT gate
This gate inverts your binary input
Truth tables
Truth tables are used with Logic gates to show if the output will be on or off.
There can be more than one logic gate in a table so this is where the depth comes from
Binary
Binary represents the flow of electricity in a computer. This happens because a computer is made up of lots of wires and circuits meaning it cannot understand normal languages. It represents whether a switch is turned on or off. 1 represents on and 0 represents off.
This is the only information a computer can hold
Key terms
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Relational and Logical Operator
<
Less than
<=
Less or equal to
Right Arrow=
More or equal to
True
OR gate
==
Both equal
!=
Both different
Not
NOT gate
And
AND gate
Right Arrow
More than
Mathematical symbols
Exponentiation ^
The power of
/
Division
DIV
Integer division, returns an integer from a division
-
Subtraction
MOD
Modular, returns the remainder from a division
plus
Addition
*
Multiplication
