CODEWITHSUNDEEP
c
bluedroid
bluedroid

Reputation: 333

compiler skipping statements while compiling?

I wrote this simple piece of code(it actually calculates sine, cosine or tangent values of x according to s,c or t given as input) which works fine until I tried to change the order of statements just a bit....this one works fine.....

#include<stdio.h>
#include<math.h>
void main()
{
char T;
float x;
printf("\nPress s or S for sin(x); c or C for cos(x); t or T for tan(x)\n\n");
scanf("%c", &T);
printf("Enter the value of x: ");
scanf("%f",&x);

if(T=='s'||T=='S')
{
    printf("sin(x) = %f", sin(x));
}
else if(T=='c'||T=='C')
{
    printf("cos(x) = %f", cos(x));
}
else if(T=='t'||T=='T')
{
    printf("tan(x) = %f", tan(x));
}
}

*BUT*as soon as I change the arrangement to the following the compiler asks for the value of x and skips the scanf for char T and returns nothing... Can anybody explain what's happening here??? 

#include<stdio.h>
#include<math.h>
void main()
{
char T;
float x;

printf("Enter the value of x: ");
scanf("%f",&x);
printf("\nPress s or S for sin(x); c or C for cos(x); t or T for tan(x)\n\n");
scanf("%c", &T);
if(T=='s'||T=='S')
{
    printf("sin(x) = %f", sin(x));
}
else if(T=='c'||T=='C')
{
    printf("cos(x) = %f", cos(x));
}
else if(T=='t'||T=='T')
{
    printf("tan(x) = %f", tan(x));
}
}

Upvotes: 1

Views: 429

Answers (1)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726799

This is because scanf for %c takes a single character - any character, including '\n'. When you hit "return" button after entering your float value, I/O system gives you the float, and buffers the "return" character. When you call scanf with %c, the character is already there, so it gives it to you right away.

To address this problem, create a buffer for a string, call scanf with %s, and use the first character of the string as your selector character, like this:

char buf[32];
printf("\nPress s or S for sin(x); c or C for cos(x); t or T for tan(x)\n\n");
scanf("%30s", buf);
T = buf[0];

Upvotes: 5

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