Trying to convert a message in its bits counterparts

February 28, 2023

I have the code below which should convert an user message input to its bits counterpart.
For example "Hi!" should be converted to
01001000
01001001
00100001

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>
#include <ctype.h>
#include <string.h>

int printbulbs(int ascii_input);
int main(void)
{
    char *Mesaj = get_string("Message: ");
    int size = strlen(Mesaj);
    int *ascii_conversion = malloc(size * sizeof(int));

    for( int i =0; i < size; i++)
    {

        ascii_conversion[i] = (int)Mesaj[i];

    }

    for ( int i = 0; i<size; i++)
    {
        printbulbs(ascii_conversion[i]);
    }

    free(ascii_conversion);
}

int printb(int ascii_input)
{
    int bits = sizeof(int) * 8;
    char* bits_message = malloc(bits+ 1);
    bits_message[bits] ='\0';

    for (int i= bits-1; i>=0; i--)
    {
        bits_message[i] = (ascii_input & 1) + '0';
        ascii_input >>= 1;

    }

    printf("%s\n", bits_message);
    free(bits_message);
    return 0;
}

Running the code I get the below result:

Message: Hi!
00000000000000000000000001001000
00000000000000000000000001101001
00000000000000000000000000100001

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But the correct result should be:

Message: Hi!
01001000
01001001
00100001

>Solution :

If sizeof( int ) is equal to 4 then you have that the expression used as an initializer in this declaration

int bits = sizeof(int) * 8;

is equal to 32.

Also to output bits there is no great sense to allocate dynamically an array as you are doing

int *ascii_conversion = malloc(size * sizeof(int));

//...

char* bits_message = malloc(bits+ 1);

Pay attention to that the code has a typo in the function name.

On the one hand, the function is called like

printbulbs(ascii_conversion[i]);
^^^^^^^^^^

But in its definition its name is different

int printb(int ascii_input)
    ^^^^^^^

Also the return type int does have a useful information. It would be better to declare it like void.

Here is a demonstration program that shows how the function can be declared and defined.

#include <stdio,h>
#include <limits.h>

void printbulbs( char c )
{
    char bits[CHAR_BIT];

    for (size_t i = 0; i < CHAR_BIT; i++)
    {
        bits[CHAR_BIT - i - 1] = ( c & 1 ) + '0';
        c = ( unsigned char )c >> 1;
    }

    printf( "%.*s", CHAR_BIT, bits );
}

int main( void )
{
    const char *message = "Hi!";

    printf( "%s ", message );

    for ( const char *p = message; *p != '\0'; ++p )
    {
        if (p != message) putchar( ' ' );
        printbulbs( *p );
    }

    putchar( '\n' );
}

The program output is