C Programming Cheat Sheet — Complete Syntax, Data Types, Functions, and Examples

Table of Contents:

C Programming Language Cheat Sheet — Complete Guide for Beginners and Professionals

The C programming language is one of the most powerful, efficient, and widely used programming languages in the world. It forms the foundation for modern languages like C++, Java, and Python.

This C Cheat Sheet provides a quick reference for all important syntax, commands, and structures in C language programming — from variables to pointers, with practical examples.

C Language Basics

Concept	Description	Example
File Extension	`.c`	`main.c`
Compiler	Used to compile code (e.g., GCC, Turbo C)	`gcc main.c -o main`
Execution	Run the compiled program	`./main`
Comment	Adds code explanations	`// single line` or `/* multi-line */`

Example:

#include <stdio.h>
int main() {
    printf("Hello, World!");
    return 0;
}

Data Types in C

Type	Keyword	Size (bytes)	Range (approx.)
Integer	`int`	2 or 4	-32,768 to 32,767
Character	`char`	1	-128 to 127
Float	`float`	4	3.4E-38 to 3.4E+38
Double	`double`	8	1.7E-308 to 1.7E+308
Void	`void`	0	N/A

Example:

int age = 25;
float height = 5.9;
char grade = 'A';

C Variables and Constants

Type	Syntax Example	Explanation
Variable	`int num = 10;`	Stores integer value
Constant	`const float PI = 3.14;`	Value cannot be changed
Global Variable	Declared outside all functions	Accessible throughout program

Operators in C

Type	Operators	Example
Arithmetic	`+ - * / %`	`a + b`
Relational	`== != > < >= <=`	`if (a > b)`
Logical	`&&
Assignment	`= += -= *= /=`	`x += 10`
Increment/Decrement	`++ --`	`i++`
Bitwise	`&	^ ~ << >>`
Ternary	`? :`	`result = (a > b) ? a : b;`

Control Statements in C

Statement	Syntax	Description
if	`if (condition) { }`	Executes if condition is true
if-else	`if (condition) else`	Executes one of two blocks
switch	`switch(expression)`	Executes based on multiple cases
break	`break;`	Exits from a loop or switch
continue	`continue;`	Skips current iteration

Example:

if (age >= 18)
    printf("Eligible to vote");
else
    printf("Not eligible");

Loops in C

Loop Type	Syntax	Usage
for loop	`for(init; condition; inc)`	Repeats known number of times
while loop	`while(condition)`	Repeats while condition is true
do-while loop	`do { } while(condition);`	Executes at least once

Example:

for(int i=1; i<=5; i++)
    printf("%d ", i);

Functions in C

Type	Syntax Example	Description
Built-in	`printf(), scanf()`	Provided by C library
User-defined	`void greet() { }`	Created by programmer
Function with return	`int sum(int a, int b)`	Returns value

Example:

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

Arrays in C

Type	Syntax Example	Usage
One-dimensional	`int arr[5];`	Store multiple values
Two-dimensional	`int matrix[3][3];`	For tables or grids

Example:

int nums[3] = {10, 20, 30};
printf("%d", nums[1]);  // Output: 20

Pointers in C

Pointers store memory addresses of variables.

Syntax:

int num = 10;
int *ptr = &num;
printf("%d", *ptr); // Output: 10

Symbol	Meaning
`&`	Address-of operator
`*`	Value-at-address operator

Strings in C

Strings are arrays of characters ending with a null character \0.

Example:

char name[20] = "C Language";
printf("Welcome to %s", name);

Function	Usage
`strlen(str)`	Find string length
`strcpy(dest, src)`	Copy string
`strcmp(s1, s2)`	Compare strings
`strcat(s1, s2)`	Concatenate strings

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File Handling in C

Mode	Meaning
`"r"`	Read mode
`"w"`	Write mode
`"a"`	Append mode
`"r+"`	Read + Write
`"w+"`	Write + Read

Example:

FILE *fp = fopen("data.txt", "w");
fprintf(fp, "Hello C!");
fclose(fp);

FAQ — C Programming Language

Q1: Why is C still important in 2025?
C is the foundation of most modern languages and operating systems, including Linux and embedded systems.

Q2: How do I run a C program online?
Use online compilers like phponline.in C Editor or GCC locally.

Q3: What is the difference between C and C++?
C++ extends C by adding object-oriented programming (classes, inheritance, polymorphism).

Q4: What are the best IDEs for C programming?
Code::Blocks, Visual Studio Code, and Eclipse CDT are great options.

Q5: How do I learn C quickly?
Practice small projects like calculators, pattern printing, and file I/O programs.