#include <stdio.h>  
#include <stdlib.h>  
// Merges two subarrays of arr[].  
// First subarray is arr[l..m]  
// Second subarray is arr[m+1..r]  
void merge(int arr[], int l, int m, int r)  
{  
int i, j, k;  
int n1 = m - l + 1;  
int n2 = r - m;  
// Create temp arrays  
int L[n1], R[n2];  
// Copy data to temp arrays  
// L[] and R[]  
for (i = 0; i < n1; i++)  
L[i] = arr[l + i];  
for (j = 0; j < n2; j++)  
R[j] = arr[m + 1 + j];  
// Merge the temp arrays back  
// into arr[l..r]  
// Initial index of first subarray  
i = 0;  
// Initial index of second subarray  
j = 0;  
// Initial index of merged subarray  
k = l;  
while (i < n1 && j < n2) {  
if (L[i] <= R[j]) {  
arr[k] = L[i];  
i++;  
}  
else {  
arr[k] = R[j];  
j++;  
}  
k++;  
} 
  // Copy the remaining elements  
    // of L[], if there are any  
    while (i < n1) {  
        arr[k] = L[i];  
        i++;  
        k++;  
    }  
   
    // Copy the remaining elements of  
    // R[], if there are any  
    while (j < n2) {  
        arr[k] = R[j];  
        j++;  
        k++;  
    }  
}  
   
// l is for left index and r is  
// right index of the sub-array  
// of arr to be sorted  
void mergeSort(int arr[], int l, int r)  
{  
    if (l < r) {  
        // Same as (l+r)/2, but avoids  
        // overflow for large l and h  
        int m = l + (r - l) / 2;  
   
        // Sort first and second halves  
        mergeSort(arr, l, m);  
        mergeSort(arr, m + 1, r);  
   
        merge(arr, l, m, r);  
    }  
}  
   
// UTILITY FUNCTIONS  
// Function to print an array  
void printArray(int A[], int size)  
{  
    int i;  
    for (i = 0; i < size; i++)  
        printf("%d ", A[i]);  
    printf("\n");  
} // Driver code  
int main()  
{  
int arr[] = { 12, 11, 13, 5, 6, 7 };  
int arr_size = sizeof(arr) / sizeof(arr[0]);  
printf("Given array is \n");  
printArray(arr, arr_size);  
mergeSort(arr, 0, arr_size - 1);  
printf("\nSorted array is \n");  
printArray(arr, arr_size);  
return 0;  
}
by

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Read inputs from stdin

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#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}