Please explain line 16 and 21 in the code

#1

please explain me line no 16 and 21 in the code

#2

int digit=in[i]-‘0’;
// if( digit==0)
//{
// print(in,out,i+1,j);
//}

in line no 16 (int digit=in[i]-‘0’;
as in['i] is character but we need integer for further processing
for example if in[i]=‘6’ then internally it contains ascii value of ‘6’ which is 54 so to get 6 from this we subtract it with ascii value of ‘0’ which is 48 hence 54-48=6.

as in question it is stated: string corresponding to 0 is " " (empty string) means nothing
so we do nothing when digit is 0;

#3

also explain the code:

for(int k=0;keypad[digit][k]!=’\0’;k++)
{
out[j]= keypad[digit][k];
print(in ,out, i+1, j+1);
}
}

#4

in these lines we are trying to place each character corresponding to the digit
and then call for recursive function

#5

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