char overflow in c

1. Cyclic nature of unsigned char:

Consider following c program:

#include<stdio.h>

void main(){

    unsigned char c1=260;

    unsigned char c2=-6;

    printf("%d  %d",c1,c2);

}

Output: 4   250 (why?)

This situation is known as overflow of unsigned char.

    Range of unsigned char is 0 to 255. If we will assign a value greater than 255 then value of variable will be changed to a value if we will move clockwise direction as shown in the figure according to number. If number is less than 0 then we have to move in anti clockwise direction.

  

Short cut formula to find cyclic value:

If number is X where X is greater than 255 then
New value = X % 256
If number is Y where Y is less than 0 then
New value = 256 – (Y% 256)

 
2. Cyclic nature of signed char:

#include<stdio.h>

int main(){

    signed char c1=130;

    signed char c2=-130;

    printf("%d  %d",c1,c2);

    return 0;

}

Output: -126   126 (why?)

This situation is known as overflow of signed char.

  Range of unsigned char is -128 to 127. If we will assign a value greater than 127 then value of variable will be changed to a value if we will move clockwise direction as shown in the figure according to number. If we will assign a number which is less than -128 then we have to move in anti clockwise direction.

Shortcut formula to find cyclic value:

If number is X where X is greater than 127 then
p = X % 256
if p <=127
New value = p
else
New value = p – 256
 If number is Y where Y is less than -128 then
 p = Y % 256
If p <= 127
New value = -p
else
New value = 256 -p 





Overflow of char data type in c programming
Overflow of int data type in c programming
Overflow of long int data type in c programming
Overflow of float data type in c programming

Overflow of double data type in c programming

Overflow of enum data type in c programming
Data type tutorial home
C tutorial home.