OVERFLOW IN char AND UNSIGNED char DATA TYPES

Introduction

Overflow means you are carrying out an operation such that the value either exceeds the maximum value or is less than the minimum value of the data type.

Program

// the program gives maximum and minimum values of data type
#include  main() { char i,j ; i = 1;
while (i > 0) // A { j = i; // B i++; // C } printf
("the maximum value of char is %d\n",j); printf
("the value of char after overflow is %d\n",i); } 

Explanation

1. This program is used to calculate the maximum positive value of char data type and the result of an operation that tries to exceed the maximum positive value.

2. The while loop is terminated when the value of i is negative, as given in statement A. This is because if you try to add 1 to the maximum value you get a negative value, as explained previously (127 + 1 gives −128).

3. The variable j stores the previous value of i as given in statement B.

4. The program determines the maximum value as 127. The value after overflow is -128.

5. The initial value of i is 1 and it is incremented by 1 in the while loop. After i reaches 127, the next value is -128 and the loop is terminated.

Points to Remember

1. In the case of signed char, if you continue adding 1 then you will get the maximum value, and if you add 1 to the maximum value then you will get the most negative value.

2. You can try this program for short and int, but be careful when you are using int. If the implementation is 4 bytes it will take too much time to terminate the while loop.

3. You can try this program for unsigned char. Here you will get the maximum value, 255. The value after overflow is 0.