Introduction
Introduction
The Von-Neuman Architecture is based on the principle of processes instructions that are stored within the computer’s main memory (RAM). When a program is opened the program code must first be copied from secondary storage(such as the HDD or SSD) into the computer’s RAM before the code can be executed.
Once the code is loaded into the RAM the Fetch-Decode-Execute cycle begins.
- Fetch an Instruction
- Decode the Instruction
- Execute the Instruction
The process above is repeated indefinitely, and is known as the fetch, decode, execute cycle.
Video
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Fetch
Fetch
In the fetch stage of the machine cycle the CPU retrieves the data located in the memory address indicated by the program counter. Once the instruction has been fetched the program counter is incremented by one.
Decode
Decode
In the decode stage of the cycle the CPU reads the instruction that has been fetched from memory and updates the registers so that they are ready for the execute stage
Execute
Execute
In the execute stage of the cycle the instruction given is executed.