Introduction of an integer in C

Vitor Ferreira

Introduction of an integer

Ask the user to enter an integer. if the user enters an integer rather than introduce such as 14 + 12. The program should show a message saying invalid character and ask to enter another number.

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3 Replies

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Vulpes13y ago
So you only want to check that the input is an integer and, if it isn't, keep going until it is.

In C# that would be :

using System;

class Program
{
static void Main()
{
int number;

while(true)
{
Console.Write("Enter an integer : ");
if(!int.TryParse(Console.ReadLine(), out number))
{
Console.WriteLine("Not a valid integer. Please try again");
}
else
{
Console.WriteLine("OK, bye");
return;
}
}
}
}

or, if you want it in C :

#include

#define MAX_TRIES 1000

int main()
{
char s[80];
int i, valid, count;

count = 0;
while(count < MAX_TRIES)
{
printf ("Enter an integer: ");
fgets(s, 80, stdin);
valid = 1;
for(i = 0; i < strlen(s) - 1; i++)
{
if(!isdigit(s[i]))
{
valid = 0;
break;
}
}
if (valid)
{
printf ("OK, bye");
return 0;
}
else
{
printf("Not a valid integer. Please try again.\n");
count++;
}
}

}
Vitor Ferreira13y ago
to introduce any character other than a number, the program should display a message of error and re-order to enter another number until the user enters a number without character
Vulpes13y ago
I'm not sure that I understand the question but try this:

using System;

class Program
{
static void Main()
{
while(true)
{
Console.Write("Enter an integer addition : ");
string reply = Console.ReadLine();
string[] items = reply.Split('+');
if (items.Length == 1)
{
Console.WriteLine("Invalid addition, please re-enter");
}
else
{
int[] numbers = new int[items.Length];
for(int i = 0; i < items.Length; i++) int.TryParse(items[i], out numbers[i]);
int sum = 0;
foreach(int number in numbers) sum += number;
Console.WriteLine("The result is {0}", sum);
Console.ReadKey();
return;
}
}
}
}