how to avoid to printing the value of charecter in C?

Hi Friends,
I wrote a program in c to print a table for ant in teger as shown below

/**----------------------------------------**/
int a,b,c;
printf("Enter the value of a\n");
scanf("%d",&a);

for(b=1; b<= 20; b++)
{
c=a*b;
printf("%d X %d = %d\n",a, b,c );
}
/**-----------------------------------------**/

This program is working fine,when i give input as a number.

However,

[COLOR=[B]DarkRed]in case,the given input is a charecter[/B],[/COLOR]
Then it is showing some different output.

 

Hi Shabbir,
Thankyou very much for your reply.
Now what is the solution?
how can i use the function "isalpha()"
to avoid the above problem

 

Check This code ( I only use cout and cin instead of scanf() and printf() )

Code:

#include <iostream>
#include <cstdlib>
#include <cctype>
using namespace std;

int valid_data(const char *data)
{
    int i=0;
    //TO Check -ve Number
    if(data[0] == '-')
        i++;
    //To check if only '-' sign is their
    if(data[i] == '\0' )
        return 1;
    while(data[i] != '\0')
    {
        if(!isdigit(data[i]))
            return 1;
        i++;
    }
    return 0;
}

int main()
{
	string n;
	cout<<"Enter Value of n : ";
	cin>>n;
	if(!valid_data(n.c_str()))
	{
	    int a = atoi(n.c_str());
        for(int i=1;i<=20;i++)
            cout<<a<<" X "<<i<<" = "<<a*i<<endl;
	}
    else
        cout<<"Invalid Value";
	return 0;
}

If you want a simpler code you read this about aoti() function

You can check whether returned value is zero or not. If it is zero then you can display message. "Invalid Value". But here we cannot check if user has entered zero (0) as value. If user has entered zero (0) as value then also your program will display "Invalid Value". Hence i do not suggest this.


Regards

 

Thanks allot!!!!