C Cheat Sheet

Hello WorldBasic C program structure

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

CommentsSingle and multi-line

// Single line
/* Multi-line
   comment */

Data typesBasic primitive types

int x = 10;
float f = 3.14;
char c = 'A';
double d = 3.14159;

If-elseConditional execution

if (x > 0) {
    printf("positive");
} else {
    printf("not positive");
}

For loopIteration

for (int i = 0; i < 10; i++) {
    printf("%d\n", i);
}

While loopCondition-based loop

while (x > 0) {
    x--;
}

SwitchMulti-way branch

switch (n) {
    case 1: break;
    default: break;
}

FunctionFunction definition

int add(int a, int b) {
    return a + b;
}

ArrayFixed-size collection

int arr[5] = {1, 2, 3, 4, 5};
arr[0] = 10;

StringsCharacter arrays

char str[] = "hello";
printf("%s", str);
#include <string.h>

Pointer declarationVariable that holds an address

int *ptr;
int x = 10;
ptr = &x;

DereferenceAccess value at address

printf("%d", *ptr);

mallocDynamic memory allocation

int *arr = (int*)malloc(5 * sizeof(int));
free(arr);