C Programming Cheat Sheet

C Programming Cheat Sheet

C Programming Cheat Sheet will guide you to work on C language with basics and advanced topics. Cheat Sheet for students, engineers, and professionals.


C language is a high-level language developed by Dennis M. Ritchie. It has been used to develop operating systems, databases, editors, etc. C language code is generally written in a text file with the extension .c


  • Structured Language
  • Execution Speed
  • Code Reusability
  • C language extends itself


Variable names in C Language are the names given to locations in memory. These locations can be an integer, characters, or real constants.

Variables in C Programming

Variable Scope

The existence of a variable in a region is called its scope, or the accessibility of a variable defines its scope:

  • Local Variables: Whenever a variable is defined in a function or a block, it can be used only in that function or block. The value of that variable cannot be accessed from outside the function.
  • Global Variables: A variable has Global Scope, if it is defined outside a function i.e., the code body, and is accessible from anywhere

User Input

To get user input in C language, use the scanf(). It is used to read the data input by the user on the console. Let us print an integer entered by the user:


Command Line Arguments

In C language, you can pass values from the command line. The arguments are placed after the program name at the time of execution. For command line arguments, set the main() function in C Language to the following, wherein argc is used to count the arguments and argv has all the arguments:


The output when we have set the command line arguments as A, B, C, D:


C Tokens are the individual words and punctuation, which is the smallest element of a program, understandable by the compiler:

  • Identifiers: Used for naming variables, functions, and arrays. Do not use keywords as identifiers.
  • Keywords: These are reserved words used in programming languages. For example, continue, if, else, double, sizeof, struct, union, etc.
  • Whitespace: White space in C language includes vertical tab, horizontal tab, blank, comments, form feed, end-of-line, etc.


Constants in C language are the values that cannot be modified once they are defined:

Constants in C



Type casting in C Language converts one type to another. In C language, we use the cast operator for type casting:


  • int to float:
  • int to double


Operators perform operations by taking one or more values, to give another value. These operations are performed on variables and values. The following are the operators in C Programming:

  • Arithmetic Operators
  • Assignment Operators
  • Arithmetic Assignment Operators
  • Relational/ Comparison Operators
  • Logical Operators
  • Unary Operators
  • Conditional Operators

Decision Making Statements

Decision-making is needed when you want a set of instructions to be executed in a condition and other sets of instructions in another condition.

  • if statement

  • if-else statement

  • if-else if-else statement

  • switch statement


Loops are used when you need to repeat a part of the program. Here are the loops:

  • while loop: Used when you want to repeat a part of the program a fixed number of times.

  • do-while loop: The do-while executes the statement first and then the condition is tested.

  • for loop: Executes a specified number of times. Initialize, test, and increment loop counter in a single line:


An array is a collection of elements, of fixed size and type, for example, a collection of 5 elements of type int:

  • Declare an array:
  • Initialize an array:
  • Two-Dimensional Arrays:

    Two Dimensional Arrays Rows and Columns Structure


An array of characters in C Language is called Strings.  The null character also has a role in C language. A string is terminated by a null character i.e. \0:

  • Create a String: We haven’t added the null character above, since the compiler adds it on its own. In addition, we haven’t added size, since it is optional.
  • Create a String with size in square brackets:

    Array of characters with index in C Programming


A function in C Language is an organized block of reusable code that avoids repeating the tasks again and again:

  • Create a Function:

  • Call a Function:

  • Function Parameters:

  • Multiple Parameters:

C – Recursion

When a function calls itself, it is called Recursion in C Language. In another sense, with Recursion, a defined function can call itself. Recursion is a programming approach, that makes code efficient and reduces LOC.

The following figure demonstrates how recursion works when we calculate Factorial in C with Recursion:

Recursion in C Language


Structures in C allow you to store data of different types. You can easily store variables of types, such as int, float, char, etc:

  • Define a Structure:

  • Declare a Structure while defining it:

  • Declare a Structure with struct:

    Declare e1e2, and e3 of type emp:

  • Access Structure Members:


Structures in C language allow you to store data of different types, whereas Unions allow storing different data types but in the same memory location:

  • Create a Union:

  • Access Union Members: Use the member access operator (.):


The C Pointer is a variable that is used to store the memory address as its value. However, to get the memory address of a variable, use the & operator:

  • The Address Operator: Access the address of a variable. Defined by &, the ampersand sign.
  • The Indirection Operator: Access the value of an address. Defined by *, the asterisk sign.

Create and Declare a Pointer:




Enums, stand for enumerations i.e., a group of constants. Use enums to name constants. In C, we use the enum keyword to create an enum:

  • Syntax:

  • Create an Enum:

  • Create an Enum Variable:

  • Assign a value to the enum variable:

    The output depends on the following:
    Enums in C

What next?

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