c - Can't printf ASCII value for scanf_s value of variable -

trying user-input value character, display ascii integer number. doesn't want it--as keep getting blank output. however, if manually assign character letter let works fine.

#include "stdafx.h" #include <stdio.h> #define eps 8.85e-12  int main() {     int x = 1, y = 2, z;    float p = 2.5, q = 4.8;    double = 2.5e-9, b;    char let;     z = 2 * y;    printf(" x/(y+z) = %.1f \n", (float)x/(y + z));     printf(" alphabet ");    scanf_s("%c", &let);    printf("ascii value of alphabet %d\n", let);     printf("insert value of b :");    scanf_s("%lf", &b);    printf("value of eps/(a*b)= %8.2e\n", eps / (a*b));    return 0; } 

as per microsoft's documentation:

unlike scanf , wscanf, scanf_s , wscanf_s require buffer size specified input parameters of type c, c, s, s, or string control sets enclosed in []. the buffer size in characters passed additional parameter following pointer buffer or variable.

so need is:

scanf_s("%c", &let, sizeof(let)); 

although, of these safe functions, they're no safer "unsafe" ones if know you're doing.

note i'm not including truly unsafe variants gets(str) or scanf ("%s",str) know , control how input you'll consume fine.