 /program for calculating header checksum/
#include<stdio.h> 
int main(){ 
    int i=0, binary_index=0, temp, j, b_temp[17], binary[17];
    unsigned long int sum=0;
    printf("\nEnter packet data\n");
    for(i=0;i<10;i++){
        scanf("%x",&temp);
        sum=sum+temp;
    }
    //finding binary of sum
    while(sum!=0){
        int bit;
        bit=sum%2;
        binary[binary_index]=bit;
        binary_index++;  
        printf("  %d ", bit);
        sum=sum/2;
    }
    //reversing
    for(i=0;i<=binary_index;i++){
        b_temp[i]=binary[i];
    }
    j=0;
    for(i=binary_index;i>=0;i--){
        binary[j] = b_temp[i]; j++;
    }
    printf("\n\nAns before adding carry bit:\n");
    for(i=0;i<=binary_index;i++){
        printf(" %d",binary[i]);
    }
    printf("\n\nAns after adding carry bit:\n");
    if(binary_index>16){
        // adding carry bit
        temp=1;
        for(i=binary_index;i>1;i--){
            if(binary[i]==1 && temp==1){binary[i]=0;temp=1;}
            else if(binary[i]==0 && temp==1) {binary[i]=1;temp=0;break;}
            else if(binary[i]==0 && temp==0) {binary[i]=0;temp=0;break;}
            else if(binary[i]==1 && temp==0) {binary[i]=1;temp=0;break;}
        }
        for(i=2;i<=binary_index;i++){
            printf(" %d",binary[i]);
        }
        // complementing ans
        for(i=0;i<=binary_index;i++){ 
            if(binary[i]==0)
            binary[i]=1;
            else if(binary[i]==1)
            binary[i]=0; 
        }
        printf("\n\nAns after 1's complement:\n");
        for(i=2;i<=binary_index;i++){ 
            printf(" %d",binary[i]);
        }
    }
    else{ 
        // complementing ans
        for(i=0;i<=binary_index;i++){
            if(binary[i]==0)
            binary[i]=1;
            else if(binary[i]==1)
            binary[i]=0;
        }
        printf("\n\nAns after 1's complement:\n");
        for(i=2;i<=binary_index;i++){
            printf(" %d",binary[i]);
        }
    }
}

created 3 years ago

C Language online compiler

Write, Run & Share C Language code online using OneCompiler's C online compiler for free. It's one of the robust, feature-rich online compilers for C language, running the latest C version which is C18. Getting started with the OneCompiler's C editor is really simple and pretty fast. The editor shows sample boilerplate code when you choose language as 'C' and start coding!

Read inputs from stdin

OneCompiler's C online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample C program which takes name as input and print your name with hello.

#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

Library Functions:

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

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
}