C program examples

Small programs you can understand, run, and change. Each example includes its logic, sample output, and the concepts to watch.

“Try in Circuit” opens a new saved copy. Your existing programs stay intact. Interactive examples accept input in the terminal; sample responses shown on each page are for you to enter.

Basic Programs

Hello World

Print a greeting and learn the smallest useful structure of a C program.

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Add Two Numbers

Read two integers interactively, validate input, and print their sum.

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Conditions

Even or Odd

Use the remainder operator to classify a positive, negative, or zero integer.

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Largest of Three Numbers

Compare three integers while keeping track of the largest value seen so far.

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Loops

Factorial

Multiply a sequence of integers with a bounded loop and handle zero factorial.

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Fibonacci Sequence

Generate Fibonacci numbers by retaining only the previous two values.

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Prime Number

Determine primality using trial division and a safe stopping condition.

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Reverse a Number

Extract decimal digits from a nonnegative integer and rebuild them in reverse order.

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Palindrome Number

Compare a number with its reversed digits to recognize numeric palindromes.

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Multiplication Table

Read three inputs in sequence and print a chosen range of multiplication facts.

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Functions

Function Example

Separate a reusable calculation from main using a typed function.

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Arrays

Array Sum

Walk through a fixed array and accumulate its values without stepping past its bounds.

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Reverse an Array

Reverse an array in place by swapping pairs from opposite ends.

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Matrix Addition

Add corresponding entries of two small matrices using nested loops.

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Strings

String Length

Count characters in a null-terminated string and distinguish length from capacity.

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Pointers

Pointer Example: Swap Two Values

Use addresses to let a function update variables that belong to its caller.

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Structures

Structure Example

Group a student name and score into one structured record.

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File Handling

File Handling in Memory

Write and read a temporary runtime file while understanding Circuit’s filesystem boundary.

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