PART A · PRESCRIBED EXERCISE 02

Find the largest of three numbers

Understand the algorithm. Run the code.
Explain the result with confidence.

Read the program Open the playground

Aim & definitionStep-by-step algorithmWorked sampleExtra test cases3 viva answers

LAB A02 · 01

Understand the task.

Aim: Find the largest of three numbers.

DEFINITION

Maximum. The maximum of three numbers is a value greater than or equal to each of the three input values.

Review the related theory in Unit 2.

LAB A02 · 02

Know what goes in and what comes out.

Three integers, each from -10000 to 10000, separated by spaces or newlines.

Sample input

12 40 25

Expected output

Largest = 40

Source programs read the documented input directly, without prompt text, so the same sample works in the embedded compiler’s STDIN field.

LAB A02 · 03

Plan the steps before writing code.

Read and validate a, b and c.
If a is at least b and at least c, choose a.
Otherwise, if b is at least a and at least c, choose b.
Otherwise choose c, then display the chosen value.

LAB A02 · 04

One complete program. Ready to run.

Find the largest of three numbersmain.c

#include <stdio.h>
int main(void)
{
    int a, b, c, largest;
    if (scanf("%d%d%d", &a, &b, &c) != 3 ||
        a < -10000 || a > 10000 || b < -10000 || b > 10000 || c < -10000 || c > 10000) {
        puts("Enter three integers from -10000 to 10000.");
        return 1;
    }
    if (a >= b && a >= c) largest = a;
    else if (b >= a && b >= c) largest = b;
    else largest = c;
    printf("Largest = %d\n", largest);
    return 0;
}

EXPECTED OUTPUT

Largest = 40

Try this program Download A02-largest-of-three.c

Compile on your own computer

gcc A02-largest-of-three.c -o program

Run the generated program and enter the sample input. The examples use standard C90-compatible syntax and explicit function declarations. For these learning programs, enter numeric values representable in the stated C types and within the documented ranges.

LAB A02 · 05

Connect each statement to its purpose.

The && operator requires both comparisons to be true.
Using >= handles ties, including three equal inputs.
Negative values still compare normally; do not initialize a maximum to zero when all inputs may be negative.
This task needs only the maximum value, not the position of every tied input.

LAB A02 · 06

Follow the sample calculation.

Step or component	What happens
Inputs	a = 12, b = 40, c = 25
First condition	12 >= 40 is false; a is not selected.
Second condition	40 >= 12 and 40 >= 25 are both true.
Result	largest = 40

LAB A02 · 07

Check more than one input.

Try this input or case	Expected behaviour
-8 -2 -11	Largest = -2
7 7 3	Largest = 7
5 5 5	Largest = 5

Time and storage

O(1) time and O(1) extra space.

Start with the sample, then test a boundary and a case that changes the result. A correct sample alone does not establish that every input is handled correctly.

LAB A02 · 08

Use the real C compiler.

Choose an example and load it into the embedded C compiler. Select I/O inside the compiler, check the sample STDIN, and press Run. Change the input or edit the source to explore a different case.

Example program

Sample input (STDIN)

12 40 25

Expected output

Largest = 40

Load the compiler when you’re ready to practise.

Your C workspace

Edit real C code and see real compiler output.

Compiler provided by OneCompiler. Opening the editor connects to that service; code and input you run are processed there. If the embed is unavailable, open the C compiler in a new tab and paste the source below.

View / copy the selected source

#include <stdio.h>
int main(void)
{
    int a, b, c, largest;
    if (scanf("%d%d%d", &a, &b, &c) != 3 ||
        a < -10000 || a > 10000 || b < -10000 || b > 10000 || c < -10000 || c > 10000) {
        puts("Enter three integers from -10000 to 10000.");
        return 1;
    }
    if (a >= b && a >= c) largest = a;
    else if (b >= a && b >= c) largest = b;
    else largest = c;
    printf("Largest = %d\n", largest);
    return 0;
}

LAB A02 · 09

Explain why the program works.

Why use && rather than ||?

To be the maximum, a must be at least both other inputs. Being at least only one is insufficient.

What happens when a and b tie for the largest?

The first matching condition selects their shared value. The required largest value remains correct.

Could a loop solve this?

Yes. Start from the first value and update the current maximum for each later value.

LAB A02 · 10

Build the next skill.

Read the viva answers, try the extra cases, and return to the lab index to mark this exercise as practised.

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