Styjun

If the variable 'S' is inside a for loop, which stores the char value of the Binary value inputted by the user,
how to append all the characters to form a String which I can pass to a ShellExecute() fucntion.

char *u="https://google.com"; 
ShellExecute(NULL, "open",u, NULL, NULL, SW_SHOWNORMAL); //this will open a webpage

^^^ Binary values should be input in such a way that 'u' is a URL that opens in the browser. This will be taken care by the user. Just referenced it.

The following, is to convert Binary -> Dec-> Char:

for(i=0; i<21; i++)
scanf("%ld",&n[i]); //Binary

for(i=0; i<21;i++)

 k=n[i], c=0, decimalNumber=0;
 while(k!=0)
 
 remainder = k%10;
 k /= 10;
 decimalNumber += remainder*pow(2,c); //Dec
 ++c;
 
 char S=decimalNumber; //Char
 .
 . //how do I join all the Char I am getting here in one String
 .
 

Using this way causes A LOT OF ISSUES, but this was the only way I figured after doing a ton of reading...

char *u1=NULL;
char *u=NULL; //just after void main()
.
.
. //after I store char in 'S'
u1=u; //'u1' stores the string as 'u' gets deallocated every loop
size_t len=strlen(u1);
u=malloc(len + 1 + 1 );
strcat(u,u1); //copies the value of 'u1' from previous iteration to 'u'
u[len]=t;
u[len+1]='';

How do I store the characters in a String variable ?

Any small help is highly appreciated, Thanks! :)

There are a number of issues in your code which may lead to memory corruption.

char *u1=malloc (sizeof 25);

I presume this is supposed to allocate 25 characters? it actually allocates sizeof(25) or sizeof(int) characters which is probably 4. You just need malloc(25).

char *u="";

This creates a read only empty string literal, you cannot modify its value.

u1=u;

This throws away the string you previously allocated and causes a memory leak.

strcat(u,u1)

The memory in u is uninitialised, you need to call memset(u, 0, len + 2) before you call this otherwise u1 will be appended after the first null character in u, u may well not contain any null characters so u1 could be written anywhere in memory.

You have a mistake there, which might well explain the garbage:

 u=malloc(len + 1 + 1 );
 strcat(u,u1);

On the malloc line (at the first iteration), you lose the u that was initialized by char *u="";.
The malloc might return an uninitalized memory area (with garbage), and strcat copies u1 AFTER the garbage.