Constants and literals - Step-by-Step Execution

Concept Flow - Constants and literals

Start

↓

Write literal value

↓

Assign to constant

↓

Use constant in code

↓

Constant value remains unchanged

↓

End

This flow shows how a literal value is assigned to a constant and used without changing its value.

Execution Sample

C

const int DAYS_IN_WEEK = 7;
int main() {
  int totalDays = DAYS_IN_WEEK * 4;
  return totalDays;
}

This code assigns a literal 7 to a constant DAYS_IN_WEEK and calculates totalDays as 7 times 4.

Execution Table

Step	Action	Variable/Constant	Value	Note
1	Declare constant DAYS_IN_WEEK	DAYS_IN_WEEK	7	Constant assigned literal 7
2	Enter main function	-	-	Program starts main
3	Calculate totalDays = DAYS_IN_WEEK * 4	totalDays	28	28 = 7 * 4
4	Return totalDays	return	28	Program returns 28
5	End	-	-	Program ends

💡 Program ends after returning totalDays value 28

Variable Tracker

Variable/Constant	Start	After Step 3	Final
DAYS_IN_WEEK	undefined	7	7
totalDays	undefined	28	28

Key Moments - 2 Insights

Why can't we change the value of DAYS_IN_WEEK after assigning it?

Because DAYS_IN_WEEK is declared as a constant (const), its value is fixed after initialization as shown in step 1 and cannot be changed later.

What is the difference between a literal and a constant here?

A literal is the actual value written in code (like 7), while a constant is a named storage (DAYS_IN_WEEK) that holds that literal and cannot be changed, as shown in steps 1 and 3.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of DAYS_IN_WEEK after step 1?

A 28

B 4

C 7

D undefined

💡 Hint

Check the value assigned to DAYS_IN_WEEK in step 1 of the execution table.

At which step is totalDays calculated?

A Step 1

B Step 3

C Step 4

D Step 2

💡 Hint

Look for the step where totalDays gets a value in the execution table.

If we tried to assign DAYS_IN_WEEK = 10 after step 1, what would happen?

A The program would give a compile-time error

B The program would ignore the assignment

C The program would compile and DAYS_IN_WEEK would be 10

D The program would run but return 40

💡 Hint

Constants declared with const cannot be changed after initialization, causing a compile error.

Concept Snapshot

Constants hold fixed values that cannot change.
Literals are actual fixed values in code.
Use 'const' keyword to declare constants.
Constants improve code safety and readability.
Example: const int DAYS = 7;
DAYS cannot be changed later.

Full Transcript

This example shows how constants and literals work in C. A literal is a fixed value like 7. We assign this literal to a constant named DAYS_IN_WEEK using the const keyword. Once assigned, DAYS_IN_WEEK cannot be changed. In the main function, we use this constant to calculate totalDays as 7 times 4, which equals 28. The program returns 28 and ends. Constants help keep values safe from accidental changes and make code easier to understand.