Stepping the EVM

Your Solidity compiles to about 140 possible opcodes. Here is what count = count + 1 actually becomes.

No variables, no registers

The EVM is a stack machine. There is nowhere to put a named value — every operation pops its arguments off a stack and pushes its result back.

ADD takes the top two items and replaces them with their sum. SLOAD takes an address off the stack and pushes back what is stored there. That is the whole model.

Look at the gas column

Six instructions. Total 5,012 gas. Five thousand of it is SLOAD and SSTORE.

The arithmetic is free by comparison. Everything you will ever read about "gas optimisation" is, at bottom, about touching storage less.

Predict

A function reads the same storage variable four times. What is the cheap fix?

Choose one answer

Read it once into a local variable and use thatMark the variable `public` so reads are optimisedNothing — the compiler caches repeated reads for you

Lock in answer

Why so restrictive

No floating point. No randomness. No network access. No system calls. No threads.

Every one of those would let two nodes reach different answers, and consensus would break. The EVM is not a small machine because nobody got round to extending it — it is small because everything it can do, thousands of machines must be able to agree on exactly.

›You will rarely write assembly, but you will read itOptional

Solidity lets you drop into raw opcodes with assembly { }. Production code uses it for things the language cannot express cheaply — reading the size of calldata, custom memory layouts, cheap hashing.

You do not need to write it. You do need to not be frightened of it, because it shows up in exactly the audited, high-value contracts most worth reading — OpenZeppelin and Uniswap both use it in hot paths.

Check

Why has the EVM no floating point arithmetic?

Choose one answer

Because rounding can differ between implementations, which would break consensusBecause it would be too slowBecause money should use integers

Check answer

Worth remembering

• The EVM is a stack machine with 32-byte words and no named variables.
• `uint256` is the natural size; smaller types can cost more due to masking.
• Storage operations dominate gas — arithmetic is nearly free by comparison.
• Cold storage reads cost 2,100, warm ones 100; cache repeated reads in a local.
• No floats, randomness or network access, because every node must reach an identical result.