Question

A very simple question. Why scanf is skipped in the first while loop.
I have tried it by using getchar() and the result is same. getchar is skipped.

If you guys dont understand what I’m talking about you can tried compile it and you guys will understand what i’m asking about.

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

typedef struct rec{
    int num;
    char pref[16];
    float point;
    struct rec* next;
}rec;

void dataInput(float*,char*);
rec* insertNode(rec*);

int main(){

    int i=1;
    rec* entr,*pt = NULL;
    entr = (rec*) malloc(sizeof(rec));
    entr->num = i;
    dataInput(&entr->point,entr->pref);
    entr->next = NULL;
    char key;
    i++;

    while(1){

        printf("Continue ? If YES press 'y',or NO press 'n'\n");
        key = getchar();
        if(key == 'n')break;
        else if(key == 'y'){
            if(!pt){
                pt = insertNode(entr);
            }else{
                pt = insertNode(pt);
            }
            dataInput(&pt->point,pt->pref);
            pt->num = i;
            i++;
            continue;
        }else{
            printf("Wrong key! Please Press again! \n");
        }

    }

    pt = entr;
    while(pt){

        printf("num : %d, pref :  %s, point: %.1f\n",
                pt->num,
                pt->pref,
                pt->point);
        pt = pt->next;
    }

    getchar();
    getchar();
    return 0;
}

void dataInput(float* point,char* pref){

    printf("Input Point\t : ");
    scanf("%f",point);

    printf("Input Pref\t : ");
    scanf("%s",pref);
}

rec* insertNode(rec* current){
    rec* newnode = (rec*)malloc(sizeof(rec));
    current->next = newnode;
    newnode->next = NULL;
    return newnode;
}

Answer 1

It’s because scanf will leave a '\n' (endline) symbol in the input buffer. This symbol will be consumed by getchar at the first iteration of this while(1) loop.