Strlen, Malloc and address arithmetic

Question

Need some help breaking down this C function. I'm stuck on the malloc line. I do not understand what the "+8" is doing and/or why it is even there. My research revealed it has something to do with address arithmetic. Also, I won't mind some help checking the rest of my breakdown (comments) of each line of code is correct.

    // Prints help message to the console
    // Returns a string
    char * helloWorld(char * name) {                                //The * is a pointer to an address. (char * name) = the address to a char pointer stored/passed via name.
        char * answer = malloc(strlen(name) + 8);                   //syntax = (cast-type*) malloc(byte-size); answer has a * because malloc returns a void pointer. The * deferences the pointer
                                                                    //and tells the program to use the value at that member address.
                                                                    //strlen returns a 
        printf("This prints to the console when you Run Tests");
        strcpy(answer, "Hello, ");                                  //This returns a pointer to the destination string dest. char *strcpy(char *dest, const char *src)
                                                                //(answer {dest}, "Hello, "{string to be copied to dest}) *dest= The value at the pointer of src("Hello, ") will be assigned.
        strcat(answer {des}, name {src});               //char *strcat(char *dest, const char *src) --> appends the string pointed to by src to the end of the string pointed to by dest.
        return answer;                                  //adds name to the end of answer. -->Hello, name.
    }

Answer 1

It is supposed that the fucntion must return a string like for example

"Hello, N6DYN"

where the name "N6DYN" is passed to the function through the parameter name.

So the magic number 8 means the size of the string "Hello, " that is stored in memory like

{ 'H', 'e', 'l', 'l', 'o', ',', ' ', '\0' }

The function can be declared and defined the following way as it is shown in the demonstration program below

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

char * helloWorld( const char * name ) 
{
    const char *hello = "Hello, ";

    char *answer = malloc( strlen( name ) + strlen( hello ) + 1 );                           

    if ( answer != NULL )
    {
        strcpy( answer, hello );                                                                           
        strcat( answer, name );
    }

    return answer;
}

int main( void )
{
    char name[100] = "";

    printf( "Enter your name: " );

    scanf( "%99s", name );

    char *hello = helloWorld( name );

    if ( hello != NULL ) puts( hello );

    free( hello );
}

Instead of these lines within the function

const char *hello = "Hello, ";

char *answer = malloc( strlen( name ) + strlen( hello ) + 1 );                           

you could also write

const char hello[] = "Hello, ";

char *answer = malloc( strlen( name ) + sizeof( hello ) );                           

that is in this case sizeof( hello ) is equal to 8 that is the same value if to write strlen( hello ) + 1.