Printf command after an if statement does not work - c

Question

I just started programming a couple of days ago. I tried to program something that calculates my CGPA. I haven't completed it yet; for example, I have to improve the menu etc. It works properly for the 1st and 3rd choice. I will do something else for the second choice. The problem is, after calculation, it doesn't print the text "qwerty" on the bottom.
#include <stdio.h>
#include <stdlib.h>
int main()
{
char h[2];
double numGrade;
double credit, percent, overallCredit, sumCredit;
double contribution=0, GPA=0, semGPA=0, CGPA=0;
int courseNum, i, semesters, k, menu;
printf("Input\n\"1\" for computing your CGPA\n\"2\" if you know each semester's GPA\n\"3\" if you know your CGPA\n");
scanf("%d", &menu);
if(menu == 1)
{
printf("Enter the number of semesters you have studied: ");
scanf("%d", &semesters);
for(k=1; k<=semesters; k++)
{
printf("Enter the number of courses you took in semester %d: ", k);
scanf("%d", &courseNum);
overallCredit = 0;
sumCredit = 0;
for(i=1; i<=courseNum; i++)
{
printf("Enter the credit of the course %d: ", i);
scanf("%lf", &credit);
overallCredit += credit;
printf("Enter your letter grade: ");
scanf("%s", h);
if(strcmp(h, "AA") == 0)
{
numGrade = 4.0;
}else if(strcmp(h, "BA") == 0)
{
numGrade = 3.5;
}else if(strcmp(h, "BB") == 0)
{
numGrade = 3.0;
}else if(strcmp(h, "CB") == 0)
{
numGrade = 2.5;
}else if(strcmp(h, "CC") == 0)
{
numGrade = 2.0;
}else if(strcmp(h, "DC") == 0)
{
numGrade = 1.5;
}else if(strcmp(h, "DD") == 0)
{
numGrade = 1.0;
}else if(strcmp(h, "FD") == 0)
{
numGrade = 0.5;
}else if(strcmp(h, "DD") == 0)
{
numGrade = 0.0;
}else
{
printf("Invalid Grade\n");
}
percent = numGrade/4.0;
contribution = percent*credit;
sumCredit += contribution;
}GPA = (sumCredit/overallCredit)*4.0;
printf("Your GPA for semester %d is: %f\n", k, GPA);
semGPA += GPA;
}CGPA = semGPA/semesters;
printf("CGPA is: %.2f", CGPA+0.005);
}else
{
printf("Enter your CGPA: ");
scanf("%lf", &CGPA);
printf("Your CGPA is: %.2f", CGPA+0.005);
}
printf("qwerty"); //This does not print.
return 0;
}

Answer 1

The problem here is that you're running into undefined behaviour! (This means anything can happen - code will work, sometimes, not work, sometimes, and maybe even wipe your hard disk, sometimes.)
This happens because you are trying to read too many characters into your h variable: you have declared it: char h[2], which can hold only one letter plus the terminating nul. But you try to read two letters into it. Declare it a bit longer: char h[3] and your code should work. But it's maybe better to be safer, and declare it longer, say char h[20];, in case the user types too much data in; alternatively, specify in the input format a maximum string length: scanf("%2s", h);, which will truncate (ignore) any letters after the second.
In your code, the scanf operation writes beyond the memory allocated to h and, thus, maybe changes other 'control' variables in the compiled code.
EDIT: PS, it may not actually be the scanf call that triggers the undefined behaviour! It could be the subsequent strcmp call - the h argument to this will not have a nul terminator and the function will then overflow the string buffer, looking for a zero.