CODEWITHSUNDEEP
cbinary-data
uma_8331
uma_8331

Reputation: 97

How a single byte can hold -128 value

In memory 128 will be stored as 10000000. Where should I place the sign bit here since whole 1 byte is occupied by number 128 if i store -128 in byte datatype?

Can you please explain me?

Upvotes: 3

Views: 1346

Answers (3)

dbush
dbush

Reputation: 225227

Signed integers are typically represented in two's complement. This means that for a given positive number, the corresponding negative number is obtained by inverting all bits then adding 1.

A negative number in two's complement will have the high order bit set. This bit becomes the sign bit.

So for a number occupying a single byte, 11111111 represents -1, 11111110 represents -2, and so forth, all the way to 10000000 which represents -128. On the high end, 01111111 represents 127.

This means that a 1 byte signed integer cannot store the value 128. If you had a 1 byte unsigned integer then 10000000 would be 128 but then it could not hold any negative numbers.

Upvotes: 10

Nicolas Martinez
Nicolas Martinez

Reputation: 787

A single byte means 8 bits, which mean you can choose from 2^8 = 256 values. In C representation for signed char (or signed integer of 1 byte) teh values chosen were from [-128, 127] including both extremes

Upvotes: 2

zhj
zhj

Reputation: 498

you could cast to unsigned char, like

char s128 = (char)128;
if((unsigned char)s128==128){
    printf("true\n");
}

Upvotes: 0

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