#include <iostream>
using namespace std;

#include <iostream>
#include <iomanip>

void make_crc_table(unsigned long crcTable[]) {
    unsigned long POLYNOMIAL = 0xEDB88320;
    unsigned long remainder;
    unsigned char b = 0;
    do {
        // Start with the data byte
        remainder = b;
        for (unsigned long bit = 8; bit > 0; --bit) {
            if (remainder & 1)
                remainder = (remainder >> 1) ^ POLYNOMIAL;
            else
                remainder = (remainder >> 1);
        }
        cout << std::hex << remainder <<endl;
        crcTable[(size_t)b] = remainder;
    } while(0 != ++b);
}

unsigned long gen_crc(unsigned char *p, size_t n, unsigned long crcTable[]) {
    unsigned long crc = 0xfffffffful;
    size_t i;
    for(i = 0; i < n; i++)
        crc = crcTable[*p++ ^ (crc&0xff)] ^ (crc>>8);
    return(~crc);
}

int main() 
{
    unsigned long crcTable[256];
    make_crc_table(crcTable);
    
    unsigned char crc_arr[10]={1,2,3,4,5,6,7,8,9,1};
    unsigned long final_crc;
    
    // Print the CRC table
    cout << "Hello, World!" << endl;
    for (size_t i = 0; i < 256; i++) {
        std::cout << std::setfill('0') << std::setw(8) << std::hex << crcTable[i];
        if (i % 4 == 3)
            std::cout << std::endl;
        else
            std::cout << ", ";
    }
    final_crc = gen_crc(crc_arr, sizeof(crc_arr), crcTable);
    cout << "Final CRC value is " << final_crc <<endl;
    return 0;
}

C++ Online Compiler

Write, Run & Share C++ code online using OneCompiler's C++ online compiler for free. It's one of the robust, feature-rich online compilers for C++ language, running on the latest version 17. Getting started with the OneCompiler's C++ compiler is 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 compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

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);

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. Function gets run only when it is called.

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
}