CSE361S Week 1 (Compact Version)

Conservation of Bits

What you get is what you assigned.

Signed and Unsigned

Signed: The most significant bit is the sign bit.
- Two's complement: Range is from -2^(w-1) to 2^(w-1) - 1.
- Created by int i = -1;
Unsigned: The most significant bit is the value bit.
- Range is from 0 to 2^w - 1.
- Created by unsigned int i = 1; or int i = 1U;

During the conversion, the binary representation of the number is the same.

For example, -1 in signed is 0b11111111 in signed. and 0b11111111 in signed is 255 in unsigned.

Any arithmetic operation in signed and unsigned follows the same rules. 0b00000000 is 0 in signed and unsigned. and 0-1=255 in unsigned but -1 in signed. (The binary representation of -1 in signed is 0b11111111 and 0b11111111 is 255 in unsigned.)

Shift Operations

Logical Shift: Shift the bits and fill in the new bits with 0. (used for unsigned numbers)
Arithmetic Shift: Shift the bits and fill in the new bits with the sign bit. (used for signed numbers)

Bytes

Byte Ordering

For Example: 0x12345678

Little Endian: The least significant byte is stored at the lowest address.
- 0x78 is stored at the lowest address.
Big Endian: The most significant byte is stored at the lowest address.
- 0x12 is stored at the lowest address.

Representing Strings

char *str = "12345";

In memory, it is stored as 0x31 0x32 0x33 0x34 0x35 with terminating null character 0x00.

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