Using pointers to return char and float values from scanf back to main function C

Question

I don't quite understand why the pointer passes the value from the scanf from info function to the main function but the function I just define in the info function does not pass back to the main function. Do I need the do while loop to achieve the goal of making sure the user inputs a value for ab and c?

    #include <stdio.h>

    void info (char *a, char *b, char *c);

    void main(void)
    {
        char lett1 = 'a', lett2 = 'b', lett3 = 'c';
        info (&lett1, &lett2, &lett3);
        printf("\n The characters chosen are: %c, %c and %c", lett1, lett2, lett3);
    }

    void info (char *a, char *b, char *c)
    {
        a = 'E';
        printf("\n Type any 2 characters then press enter:  "); 
        fflush(stdin);
        scanf(" %c", b);
        do{
            scanf(" %c", c);
        }while (c == NULL);
    }

The second piece of code is where I am also using pointer and scanf but I can't get the programme to work. When I use the sections I have commented out, (type = 'A' or type = 'B') it works but not with the scanf. Furthermore, the value defined in input function is never moved to the main function.

    #include <stdio.h>

    void input (char *type, float *BU_Dist, float *SC_Dist, float *DC_Dist);

    void main (void)
    {
        char type_M = 'Z';
        float BU_Dist_M, SC_Dist_M, DC_Dist_M;
        input (&type_M, &BU_Dist_M, &SC_Dist_M, &DC_Dist_M);
        printf("Value back in the main is %c", type_M);
    }

    void input (char *type, float *BU_Dist, float *SC_Dist, float *DC_Dist)
    {
        printf("Which car type (A/B):");
        fflush(stdin);
        scanf("%c", type);
        //type = 'A'
        //type = 'C';
        printf ("%c \n\n", type);
        if(type == 'A'|| type == 'B'||type == 'a'||type == 'b') { 
        printf("\nGreat! &c selected! \n", type);
        }else{
        type = 'A';
        printf("\nInvalid value selected, type has been defaulted to %c \n", type);
        }
    }

Any help understanding how both pointers and scanf work together when in function other than the main one would be much appriecated. Thanks

Answer 1

In the commented section you are assigning char value to a char* resulting in undefined behavior.

Also in this code also you do type='A' which is basically not covered as code didnt go to else part I suppose.

If you want to assign you will do it like this *type='A' .

For comparison you need to dereference the char* to get the value.

if(*type == 'A'|| *type == 'B'||*type == 'a'||*type == 'b') {

Also fflush() is meant to be used over output stream not input stream. What you did invokes undefined behavior.