View and pure functions in Blockchain / Solidity - Step-by-Step Execution

Concept Flow - View and pure functions

Call function

↓

Is function view or pure?

No→Modify state allowed

Yes↓

Read-only or no state access

↓

Return data without state change

↓

End function

This flow shows how view and pure functions are called and how they only read or do not access state, returning data without changing blockchain state.

Execution Sample

Blockchain / Solidity

contract Example {
  uint x = 10;
  function getX() public view returns (uint) {
    return x;
  }
  function add(uint a, uint b) public pure returns (uint) {
    return a + b;
  }
}

This contract has a view function that reads state and a pure function that only uses inputs to return a result.

Execution Table

Step	Function Called	State Access	Action	Return Value
1	getX()	Reads state variable x	Returns x value	10
2	add(3, 4)	No state access	Calculates sum 3+4	7
3	getX()	Reads state variable x	Returns x value	10
4	add(10, 20)	No state access	Calculates sum 10+20	30
5	End	-	No more calls	-

💡 Execution stops after all function calls return their results without modifying state.

Variable Tracker

Variable	Start	After getX()	After add(3,4)	After getX() again	After add(10,20)	Final
x	10	10	10	10	10	10
a	-	-	3	-	10	-
b	-	-	4	-	20	-

Key Moments - 2 Insights

Why does the view function getX() not change the state variable x?

Because view functions are read-only and cannot modify state, as shown in execution_table rows 1 and 3 where x remains 10.

Why can the pure function add() not access the state variable x?

Pure functions do not read or modify state; they only use input parameters, as seen in execution_table rows 2 and 4 where add() uses only a and b.

Visual Quiz - 3 Questions

Look at the execution_table, what is the return value of getX() at step 3?

A 7

B 10

C 30

D 0

💡 Hint

Check the 'Return Value' column at step 3 in execution_table.

At which step does the function add() calculate the sum of 10 and 20?

A Step 4

B Step 1

C Step 2

D Step 5

💡 Hint

Look at the 'Function Called' and 'Action' columns in execution_table.

If the function getX() tried to modify x, what would happen according to the concept flow?

A It would succeed and change x

B It would ignore the change silently

C It would cause an error because view functions cannot modify state

D It would convert to a pure function

💡 Hint

Refer to the decision step 'Is function view or pure?' in concept_flow.

Concept Snapshot

View and pure functions in blockchain:
- View functions read state but do not modify it.
- Pure functions neither read nor modify state.
- Both return data without changing blockchain state.
- Use view for reading variables.
- Use pure for calculations using only inputs.

Full Transcript

This visual execution shows how view and pure functions work in blockchain smart contracts. View functions can read state variables but cannot change them, while pure functions cannot read or change state and only use their input parameters. The example contract has a state variable x set to 10. The getX() function is view and returns x's value without changing it. The add() function is pure and returns the sum of two inputs without accessing state. The execution table traces calls to these functions, showing their actions and return values. Variables like x remain unchanged throughout. Key moments clarify why view functions cannot modify state and why pure functions cannot access state. The quiz tests understanding of return values, function steps, and rules about state modification. The snapshot summarizes the key rules for using view and pure functions in blockchain programming.