README

Basic syntax and functions from the C programming language.

Summary

• README
  • Comments
  • Data types
  • Escape Sequences
  • Conditional Instructions
  • Iterative Statements
  • Functions & Recursion
  • Pointers
  • Arrays
  • Strings
  • Structures
  • File Handling
  • Dynamic Memory Allocation

---

• Boilerplate Code

#include<stdio.h> 
int main()
{
 return(0);
}

• printf function: It is used to show output on the screen printf("Hello World!")

• scanf function: It is used to take input from the user scanf("placeholder", variables)

Comments

A comment is the code that is not executed by the compiler, and the programmer uses it to keeptrack of the code.

• Single line comment

// It's a single line comment

• Multi-line comment

/* It's a multi-line (^)
comment*/

Data types

The data type is the type of data

• Character type: Typically a single octet(one byte). It is an integer type char variable_name;

• Integer type: The most natural size of integer for the machine int variable_name;

• Float type: A single-precision floating-point value float variable_name;

• Double type: A double-precision floating-point value double variable_name;

• Void type: Represents the absence of the type void

Escape Sequences

It is a sequence of characters starting with a backslash, and it doesn't represent itself when usedinside string literal.

• Alarm or Beep: It produces a beep sound \a

• Backspace: It adds a backspace \b

• Form feed: \f

• Newline: Newline Character \n

• Carriage return: \r

• Tab: It gives a tab space \t

• Backslash: It adds a backslash \\

• Single quote: It adds a single quotation mark \'

• Question mark: It adds a question mark \?

• Octal No: It represents the value of an octal number \nnn

• Hexadecimal No: It represents the value of a hexadecimal number \xhh

• Null: The null character is usually used to terminate a string \ 0

Conditional Instructions

Conditional statements are used to perform operations based on some condition.

• If Statement

if{ (/* condition */)
/* code */}

• If-else Statement

if{ (/* condition */)
/* code */}

else/*Code*/{ (^)
}

• if else-if Statement

if(condition) {
// Statements; 

}else (^) if (condition){
// Statements;}
else// Statements{ (^)
}

• Switch Case Statement

It allows a variable to be tested for equality against a list of values (cases).

switch (expression)
{
case constant-expression:
statement1;
statement2;
break;
case constant-expression:
statement;
break;
...
default:
statement;
}

Iterative Statements

Iterative statements facilitate programmers to execute any block of code lines repeatedly andcan be controlled as per conditions added by the programmer.

• while Loop: It allows execution of statement inside the block of the loop until the condition of loop succeeds.

while{ (/*condition*/)
/*code*/}
int =5;
while(i!=0){
    i--;
}

do{
    i--;
    printf(i);
}while(i!=0)
    
4
    3
    2
    1
    0 break
    
    4
    3
    2
    1
    0
    break
    
            

• do-while loop: It is an exit controlled loop. It is very similar to the while loop with one difference, i.e., the bodyof the do-while loop is executed at least once even if the expression is false

do{

/*code*/} while (/*condition*/ (^) );

• for loop: It is used to iterate the statements or a part of the program several times. It is frequently used totraverse the data structures like the array and linked list.

for{ (int i = 0 ; i < count; i++)
/* code */}

• Break Statement: break keyword inside the loop is used to terminate the loop break;

• Continue Statement: continue keyword skips the rest of the current iteration of the loop and returns to the startingpoint of the loop

continue;

Functions & Recursion

Functions are used to divide an extensive program into smaller pieces. It can be called multipletimes to provide reusability and modularity to the C program.

• Function Definition:

return_type //code to be executed function_name (data_type parameter...){
}

• Recursion: Recursion is when a function calls a copy of itself to work on a minor problem. And the functionthat calls itself is known as the Recursive function.

void{ recurse()

.recurse.. .. .(.).; (^)
.}.. .. ...

Pointers

Pointer is a variable that contains the address of another variable,

• Declaration:

datatype *var_name;

Arrays

An array is a collection of data items of the same type.

• Declaration

data_type array_name[array_size];

int array[5]= {1,2,3,4,5,6}
array[0] = 0;
array[5] = 6;
array[i++

• Accessing element

int variable_name = array[index];

Strings

A string is a 1-D character array terminated by a null character ('\0')

• Declaration:

char str_name[size];
char name[4] = {n,h,o,n, , a}

• gets() function: It allows you to enter multi-word string

gets("string");

• puts() function: It is used to show string output

puts("string");

• String Functions strlen(): It is used to calculate the length of the string

strlen(string_name);

• strcpy() function: It is used to copy the content of second-string into the first string passed to it

strcpy(destination, source);

• strcat() function: It is used to concatenate two strings

strcat(first_string, second_string);

• strcmp() function: It is used to compare two strings

strcmp(first_string, second_string);

Structures

The structure is a collection of variables of different types under a single name. Definingstructure means creating a new data type.

• Structure syntax:

struct{ structureName

dataType member1dataType member2;; (^)
.}.;.

• typedef keyword: typedef function allows users to provide alternative names for the primitive and user-defineddata types.

typedef{ struct structureName

dataType member1dataType member2;; (^)

.}.new_name. (^) ;

File Handling

A set of methods for handling File IO (read/write/append) in C language

• FILE pointer

FILE *filePointer;

• Opening a file

It is used to open file in C.

filePointer = fopen(fileName.txt, w)

• fscanf() function

It is used to read the content of file.

fscanf(FILE *stream, const char*format, ...)

• fprintf() function

It is used to write content into the file.

fprintf(FILE *fptr, const char*str, ...);

• fgetc() function

It reads a character from a file opened in read mode. It returns EOF on reaching the end of file.

fgetc(FILE *pointer);

• fputc() function

It writes a character to a file opened in write mode

fputc(char, FILE *pointer);

• Closing a file

It closes the file.

fclose(filePointer);

Dynamic Memory Allocation

A set of functions for dynamic memory allocation from the heap. These methods are used to usethe dynamic memory which makes our C programs more efficient

• malloc() function

Stands for 'Memory allocation' and reserves a block of memory with the given amount of bytes.

ptr = (castType*) malloc(size);

• calloc() function

Stands for 'Contiguous allocation' and reserves n blocks of memory with the given amount ofbytes.

ptr = (castType*)calloc(n, size);

• free function

It is used to free the allocated memory.

 free(ptr);

• realloc() function

If the allocated memory is insufficient, then we can change the size of previously allocatedmemory using this function for efficiency purposes

ptr = realloc(ptr, x);