C Programming Cheat Sheet

25 Jul C Programming Cheat Sheet

Posted at 17:19h in C by Studyopedia Editorial Staff 0 Comments

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

Introduction

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

Features

Structured Language
Execution Speed
Code Reusability
C language extends itself

Variables

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:

#include <stdio.h>

int main() {

int i;

// Asks the user to enter a number

printf("Enter a number = ");

scanf("%d",&i);

// Displays the number entered by the user above

printf("\nThe number entered by user = %d ",i);

return 0;

}

Output

Enter a number = 10

The number entered by user = 10

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:

#include<stdio.h>

int main(int argc, char *argv[] ) {

printf("Displaying the command line arguments...\n");

printf("Count of arguments = %d\n", argc);

printf("\nFirst argument = %s\n", argv[1]);

printf("First argument = %s\n", argv[2]);

printf("Third argument = %s\n", argv[3]);

printf("Fourth argument = %s\n", argv[4]);

return 0;

}

Output

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

Displaying the command line arguments...

Count of arguments = 5

First argument = A

First argument = B

Third argument = C

Fourth argument = D

Tokens

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

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

Constants in C

Example:

const int a = 50; // Integer constant

const float b = 33.25; // Real constant

const char c = 'C'; // Character constant

Typecasting

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

(type_name)value

Example:

int to float:

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int a = 13, b = 3;
float f = (float) a/ b;
printf("Float = %f\n", f); // Output Float = 4.333333
int to double

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int a = 20, b = 7;
double f = (double) a/ b;

printf("Double = %f\n", f);// Output: Double = 2.857143

Operators

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

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if(condition true)
statement gets executed;
if-else statement

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if(condition true)
statement gets executed;
else
another statement gets executed;
if-else if-else statement

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if(condition true)
     statement gets executed;
else if()
     statement gets executed;
else
    another statement gets executed;

switch statement

switch(expression) {

case value1 :

break;

case value2 :

break;

case value3 :

break;

default :

}

Loops

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.

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loop counter initialization;
while (condition is true)
{
   statement1;
   statement2;
   .
   .
   .
   loop counter increment;
}
do-while loop: The do-while executes the statement first and then the condition is tested.

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loop counter initialization;
do
{
   Statement1;
   Statement2;
   .
   .
   .
   loop counter increment;
} while(condition is true)
for loop: Executes a specified number of times. Initialize, test, and increment loop counter in a single line:

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for (initialize loop counter; test loop counter; loop counter increment)
{
   Statement1;
   Statement2;
   .
   .
   .
}

Arrays

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:

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int marks[3];
Initialize an array:

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int marks[3] = {90, 75, 88} ;
Two-Dimensional Arrays:

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int marks[3][3];

Strings

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.

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char celeb[] = "Lionel";
Create a String with size in square brackets:

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char website[] = {'S', 't', 'u', 'd', 'y', 'o', 'p', 'e', 'd', 'i', 'a','\0'};

Functions

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

Create a Function:

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void demoFunction() {
// write the code
}
Call a Function:

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demoFunction();
Function Parameters:

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void demoFunction(int rank) { }
Multiple Parameters:

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void demoFunction(char player[], int rank, int points) { }

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

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:

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struct emp
{
    char name[15];
    int age;
    char zone[10];
    float salary;
};
Declare a Structure while defining it:

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struct emp
{
    char name[15];
    int age;
    char zone[10];
    float salary;
};  e1, e2, e3;
Declare a Structure with struct:

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struct emp
{
    char name[15];
    int age;
    char zone[10];
    float salary;
};

Declare e1, e2, and e3 of type emp:

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struct emp e1, e2;
Access Structure Members:

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e1.name
e1.age
e1.zone
e1.salary

Unions

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:

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union Demo
{
    int a;
    float b;
    int c;
    char d[15];
};
Access Union Members: Use the member access operator (.):

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union Demo demo;

demo.a = 5;
demo.b = 15.6;
demo.c = 34.657;

Pointers

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:

int* a;

Example:

#include <stdio.h>

int main()

{

// Integer variable a

int a = 10;

// A pointer variable b storing the address of the variable a

int* b = &a;

printf("Integer Value = %p",&a);

printf("\nThe memory address of the variable %p",&a);

printf("\nThe memory address of the variable a with the pointer = %p",b);

return 0;

}

Output

Integer Value = 0x7ffcfc4e1d34

The memory address of the variable 0x7ffcfc4e1d34

The memory address of the variable a with the pointer = 0x7ffcfc4e1d34

Enums

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:

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enum enum_name {
  enum_item1,
  enum_item2,
  enum_item3,
  .
  .
  .
  enum_itemn
};
Create an Enum:

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enum Directions {
  NORTH,
  SOUTH,
  EAST,
  WEST
}
Create an Enum Variable:

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enum Directions d1;

Assign a value to the enum variable:

// Create Enum variables

enum Directions d1, d2;

// Assign value to the Enum variable d1

d1 = NORTH;

printf("%d\n", d1); // Output: 0

// Assign value to the Enum variable d2

d2 = SOUTH;

printf("%d", d2); // Output: 1

The output depends on the following:

What next?

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25 Jul C Programming Cheat Sheet

Introduction

Features

Variables

Variable Scope

User Input

Command Line Arguments

Tokens

Constants

Typecasting

Operators

Decision Making Statements

Loops

Arrays

Strings

Functions

C – Recursion

Structures

Unions

Pointers

Enums

What next?

Studyopedia Editorial Staff

No Comments

Post A Comment

Tutorials

Cheat Sheet

Quiz

Interview Questions & Answers

25 Jul C Programming Cheat Sheet

Introduction

Features

Variables

Variable Scope

User Input

Command Line Arguments

Tokens

Constants

Typecasting

Operators

Decision Making Statements

Loops

Arrays

Strings

Functions

C – Recursion

Structures

Unions

Pointers

Enums

What next?

Studyopedia Editorial Staff

No Comments

Post A Comment

Tutorials

Cheat Sheet

Quiz

Interview Questions & Answers

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