John Von Neumann

Von Neumann Architecture: A von Neumann architecture machine, designed by physicist and mathematician John von Neumann (1903–1957) is a theoretical design for a stored program computer that serves as the basis for almost all modern computers.


MAR(Memory Address Register): In a computer, the Memory Address Register (MAR) is the CPU register that either stores the memory address from which data will be fetched from the CPU, or the address to which data will be sent and stored. In other words, MAR holds the memory location of data that needs to be accessed.




MDR(Memory Data Register): A memory buffer register (MBR) or memory data register (MDR) is the register in a computer's processor, or central processing unit, CPU, that stores the data being transferred to and from the immediate access storage. ... When data is fetched from memory and placed into the MDR, it is written to go in one direction.




Program Counter: A program counter is a register in a computer processor that contains the address (location) of the instruction being executed at the current time. As each instruction gets fetched, the program counter increases its stored value by 1.


Accumulator: In a computer's central processing unit (CPU), an accumulator is a register in which intermediate arithmetic and logic results are stored. ... Modern computer systems often have multiple general purpose registers that operate as accumulators, and the term is no longer as common as it once was.




ALU(Arithmetic Logic Unit): An arithmetic logic unit is a combinational digital electronic circuit that performs arithmetic and bitwise operations on integer binary numbers. This is in contrast to a floating-point unit, which operates on floating point numbers.






CU(Control Unit): The control unit (CU) is a component of a computer's central processing unit (CPU) that directs the operation of the processor. It tells the computer's memory, arithmetic/logic unit and input and output devices how to respond to the instructions that have been sent to the processor.




Cache: Definition of: cache (1) To store data locally in order to speed up subsequent retrievals. Pronounced "cash." See Web cache and browser cache. (2) Reserved areas of memory (RAM) in every computer that are used to speed up processing.




Fetch/Execute: The fetch execute cycle is the basic operation (instruction) cycle of a computer. During the fetch execute cycle, the computer retrieves a program instruction from its memory. It then establishes and carries out the actions that are required for that instruction.




Busses: The bus in a PC is the common hardware interface between the CPU and peripheral devices. Parallel buses use multiple lines (wires) for data. Serial buses use one line for data.

Embedded Systems

An embedded system is a combination of computer hardware and software that is fixed in capability or programmable. This means you don't need to use a keyboard and mouse to operate an appliance.
-vending machines
-microwaves
-freezers
-dish washers
-printer
-washing machine
-car

Binary and Hexadecimal

Hexadecimal (or hex) is a base 16 system used to simplify how binary is represented. A hex digit can be any of the following 16 digits: 0 1 2 3 4 5 6 7 8 9 A B C D E F.

Each hex digit reflects a 4-bit binary sequence.

This table shows each hex digit with the equivalent values in binary and denary.

There are a number of very common needs for a computer, including the need to store and view data.

Computers use electrical signals that are on or off, so they have to see everything as a series of binary numbers. This data is represented as a sequence of 1s and 0s (on and off). All data that we want a computer to process needs to be converted into this binary format.

What is binary?

Binary is a number system that only uses two digits: 1 and 0. All information that is processed by a computer is in the form of a sequence of 1s and 0s. Therefore, all data that we want a computer to process needs to be converted into binary.

The binary system is known as a ‘base 2’ system. This is because:

• there are only two digits to select from (1 and 0)
• when using the binary system, data is converted using the power of two.

Examples Of Binary


8 4 2 U

0 1 0 1 = 5

1 1 1 1 = 15

1 0 1 1 = 11

0 0 0 1 = 1

128 64 32 16 8 4 2 U
00000111=7
10000000=128
00001101=14
11111111=255

Boolean

Logic gates 1

There are different types of logic gate, depending upon what the gate is needed to do.

OR gates

An OR gate will give a high output if any of the inputs is high. For example, in a simple lighting circuit with two switches in parallel the lamp will light if either switch is pressed.

The relationship between the inputs and the output can be captured in a truth table. A and B represent the inputs and Q is the output.

Truth table for an OR gate

A	B	Q
0	0	0
0	1	1
1	0	1
1	1	1

OR gate symbol

AND gates

An AND gate will give a high output only if all of the inputs are high. For example, in a simple lighting circuit with two switches in series the lamp will light only if both switches are pressed.

Truth table for an AND gate

A	B	Q
0	0	0
0	1	0
1	0	0
1	1	1

AND gate symbol


http://wiki.schoolcoders.com/gcse/computational-logic/logic-gates/

Introduction

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