C PROGRAMMING PROGRAM • DECISION MAKING

Check Whether a Number Is Positive, Negative or Zero

Learn how to check whether a number is positive, negative or zero using a clear C program.

Beginnerif-elseComparisonThree-way decision

PROBLEM UNDERSTANDING

Input and expected output

Sample input

-8.5

Sample output

Negative

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    double number;

    printf("Enter a number: ");
    scanf("%lf", &number);
    if (number > 0)
        printf("Positive\n");
    else if (number < 0)
        printf("Negative\n");
    else
        printf("Zero\n");
    return 0;
}

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

No line selected

EXPECTED OUTPUT FOR THE SAMPLE

Negative

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Compare the number with zero using an if–else-if chain.
Display the computed result.

Compare the number with zero using an if–else-if chain.

EFFICIENCY

Time and space complexity

Time complexity

O(1)

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

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Initialize variables before using their values.

Check this

Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.