How to Use the C Compiler

To use the C Compiler, follow these steps:

  1. In the code editor, write your C code.
  2. Click the "RUN" button to compile and run your code.
  3. The output will be displayed in the console below the code editor.

Taking Inputs

In C, you can take inputs from the user in various ways. Here are some examples:

String Input

#include <stdio.h>

int main() {
    char input[100];
    printf("Enter a string: ");
    fgets(input, sizeof(input), stdin);
    printf("You entered: %s", input);
    return 0;

Number Input

#include <stdio.h>

int main() {
    int num;
    printf("Enter a number: ");
    scanf("%d", &num);
    printf("You entered: %d", num);
    return 0;

Importing Libraries

C has a rich set of built-in libraries that can be used in your programs. Here are some examples:

Using the Math Library

#include <stdio.h>
#include <math.h>

int main() {
    double result = sqrt(25);
    printf("Square root of 25 is %.2f", result);
    return 0;

Using the Array Functions

#include <stdio.h>

int main() {
    int arr[5] = {1, 2, 3, 4, 5};
    for(int i = 0; i < 5; i++) {
        printf("%d ", arr[i]);
    return 0;

Syntax 101

C is a general-purpose, procedural computer programming language. Here's a primer on the major syntax basics of C:


Variables in C must be declared with the type of data that they will store.

char name[] = "John Doe"; // Variable assignment
int age = 25; // Variable assignment

Control Structures

C includes control structures such as if, else, for, while, and switch.

// If-Else
if (age > 18) {
} else {

// For loop
for (int i = 0; i < 5; i++) {
    printf("%d", i);


Functions in C are defined with the type of value they will return.

void greet(char name[]) {
    printf("Hello, %s", name);

greet("John Doe"); // Calls the function with "John Doe" as the argument

C Online Test

A C online test is an effective way to assess an individual's C programming skills, especially in the context of systems programming. These tests typically include a mix of theoretical questions and practical coding challenges. By attempting these tests, candidates can demonstrate their understanding of C concepts, their problem-solving abilities, and their proficiency in writing efficient code. C online tests are commonly used in technical interviews, coding bootcamps, and online learning platforms to gauge a learner's understanding and proficiency in C.