State variables in Blockchain / Solidity - Step-by-Step Execution

Concept Flow - State variables

Contract deployed

↓

State variables created in storage

↓

Function called

↓

Read or update state variables

↓

State variables persist after function ends

↓

Next function call uses updated state

State variables are stored on the blockchain and keep their values between function calls in a smart contract.

Execution Sample

Blockchain / Solidity

contract Example {
  uint count;
  function increment() public {
    count = count + 1;
  }
  function getCount() public view returns (uint) {
    return count;
  }
}

This contract has a state variable 'count' that increments each time 'increment' is called and can be read with 'getCount'.

Execution Table

Step	Action	State Variable 'count'	Output
1	Contract deployed	0 (default)	None
2	Call increment()	count = 0 + 1 = 1	None
3	Call getCount()	count = 1	Returns 1
4	Call increment()	count = 1 + 1 = 2	None
5	Call getCount()	count = 2	Returns 2
6	End of calls	count = 2	State persists on blockchain

💡 Execution stops after calls; state variable 'count' keeps its last value on blockchain.

Variable Tracker

Variable	Start	After Step 2	After Step 4	Final
count	0	1	2	2

Key Moments - 2 Insights

Why does the value of 'count' not reset to 0 after each function call?

Because 'count' is a state variable stored on the blockchain, it keeps its value between calls as shown in steps 2, 3, 4, and 5 in the execution_table.

What happens if we call 'getCount' before any 'increment' calls?

The value returned would be 0, the default initial value of the state variable 'count', as shown in step 1 where 'count' starts at 0.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'count' after the first call to increment()?

A 0

B 1

C 2

D Undefined

💡 Hint

Check Step 2 in the execution_table where 'count' is updated to 1.

At which step does the 'getCount()' function return the value 2?

A Step 5

B Step 3

C Step 2

D Step 4

💡 Hint

Look at Step 5 in the execution_table where 'getCount()' returns 2.

If we never call 'increment()', what will 'getCount()' return?

A Error

B 1

C 0

D Undefined

💡 Hint

Refer to Step 1 in the execution_table where 'count' starts at 0.

Concept Snapshot

State variables store data permanently on the blockchain.
They keep their values between function calls.
Declared inside contracts but outside functions.
Updated by functions and persist after execution.
Used to track contract state like counters or balances.

Full Transcript

State variables in blockchain smart contracts are special variables that store data permanently on the blockchain. When a contract is deployed, these variables are created in the blockchain's storage with default values. Functions in the contract can read or update these state variables. Unlike local variables, state variables keep their values between function calls, so changes persist on the blockchain. For example, a 'count' variable can be incremented by calling a function, and its updated value remains stored for future calls. This behavior is shown step-by-step in the execution table, where 'count' starts at 0, increments to 1, then 2, and can be read anytime. This persistence is key to tracking contract state like balances or counters.