Update realgu.md

Author: ChengruiGu

realgu.md

@@ -56,6 +56,32 @@ func stf(parent types.Block, block types.Block, state state.StateDB) (state.Stat
 ```
 问题: what exactly does a 'state' contains? what are the tries?
 
+### 2024.02.12
+Ethereum state is stored in four different modified merkle patricia tries (MMPTs):
+- Transaction Trie
+- Receipt Trie
+- World State Trie
+- Account State Trie
+
+计算机组成课flashback：  
+
+1 word = 32 bytes, 1 byte = 8 digits = 2 digits in hexadecimal  
+
+The EVM stack has a maximum size of 1024 items. PUSH -> PUSH -> ADD  
+Also there's a program counter and JUMP. But where is compare and jump insn like bne, bge, blt?  
+And there's an available gas counter.  
+
+
+EVM memory is a byte array of 2<sup>256</sup> (or practically infinite) bytes . All locations in memory are well-defined initially as zero.  
+MSTORE takes two values from the stack: an address offset and a 32-byte value. It then writes the value to memory at the specified offset.  
+
+In EVM, memory is dynamically allocated in multiples of 1 word “pages”. Gas is charged for the number of pages expanded.  
+MSIZE: number of words/pages allocated  
+
+Storage can only be accessed via the code of its associated account. External accounts don't have code and therefore cannot access their own storage.  
+
+SSTORE takes two values from the stack: a storage slot and a 32-byte value. It then writes the value to storage of the account. So an account have associated storage
+
 
 
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