Finding the largest of three numbers is one of the first real decisions a C program has to make. It sounds simple, but it teaches you conditional logic, how the if-else ladder works, and why wrapping repeated logic in a function pays off immediately. This post shows three approaches — a plain if-else, a ternary one-liner, and a reusable function — so you can see how each trades off readability against compactness.
Method 1 — if-else Ladder
The most readable approach. Check each number in turn; the first condition that is true wins.
#include <stdio.h>
int main(void)
{
int a, b, c;
printf("Enter three numbers: ");
scanf("%d %d %d", &a, &b, &c);
if (a >= b && a >= c)
printf("Largest: %d\n", a);
else if (b >= a && b >= c)
printf("Largest: %d\n", b);
else
printf("Largest: %d\n", c);
return 0;
}
Method 2 — Ternary Operator
A nested ternary resolves the same logic in a single expression. Useful when you need the result as a value rather than printing directly.
#include <stdio.h>
int main(void)
{
int a, b, c, largest;
printf("Enter three numbers: ");
scanf("%d %d %d", &a, &b, &c);
largest = (a >= b) ? ((a >= c) ? a : c) : ((b >= c) ? b : c);
printf("Largest: %d\n", largest);
return 0;
}
Method 3 — Reusable Function
When the same comparison appears in multiple places, pull it into a function. main() stays clean, and the logic is easy to test in isolation.
#include <stdio.h>
int largest_of_three(int a, int b, int c)
{
if (a >= b && a >= c)
return a;
if (b >= a && b >= c)
return b;
return c;
}
int main(void)
{
int a, b, c;
printf("Enter three numbers: ");
scanf("%d %d %d", &a, &b, &c);
printf("Largest: %d\n", largest_of_three(a, b, c));
return 0;
}
How to Compile and Run
gcc -ansi -Wall -Wextra -o largest largest.c
./largest
Sample Input and Output
Enter three numbers: 14 72 31
Largest: 72
Enter three numbers: -5 -5 -5
Largest: -5
Enter three numbers: 100 100 99
Largest: 100
Code Explanation
Method 1 uses a two-condition check for each candidate: a >= b && a >= c confirms that a is at least as large as both others. Using >= instead of > handles ties correctly — when two or three numbers are equal, the first matching branch wins and any of the equal values is printed, which is correct.
Method 2 nests two ternary expressions. Read it inside-out: (a >= c) ? a : c picks the larger of a and c; the outer ternary selects that result only when a >= b, otherwise falling through to the b vs c comparison.
Method 3 separates the concern from main(). The function returns early as soon as a winner is identified — no else needed because return exits the function immediately. If neither a nor b wins, c must be largest (or tied for largest), so the final return c is always correct.
What This Program Teaches
- How
if-elseladders evaluate conditions top to bottom and stop at the first true branch - How to use the ternary operator
? :to produce a value from a condition - Why returning early from a function is cleaner than deeply nested
elseblocks - How to handle ties: using
>=instead of>makes all three methods correct when numbers are equal
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