02. Bits, Bytes, and Integers

'Computer Systems: A Programmer's Perspective 3rd (Randal E. Bryant)'를 주교재로 한 시스템 소프트웨어 강의 수업자료를 복습하며 정리한 것

---

Encoding Byte Values

• Byte = 8bits
  • Binary : 00000000 ~ 11111111
  • Decimal : 0 ~ 255
  • Hex : 00 ~ FF

 

Integers

• 음수의 표현
  • Signed-magnitude
  • One's complement
  • Two's complement - MSB(Most Significant Bit) indicates sign (0 - nonnegative, 1 - negative)
• Conversion
  • Two's Complement to Unsigned
    • 첫번째 bit가 Large negative weight 에서 Large positive weight가 됨
  • Casting(Expression Evaluation)
    • 한 expression에 unsigned와 signed가 함께 있다면, signed value가 암묵적으로 unsigned로 cast된다.

 

Representations in memory

• Byte-Oriented Memory Organization
  • system provides private address spaces to each process
• Machine Words
  • word size
  • Until recently, most machines used 32 bits(4 bytes) as word size(Limits address to 4GB(2^32 bytes)
  • Nowadays, machines have 64 bit word size(Potentially could have 18EB(exabytes) of addressable memory)
  • pointer type의 크기 == word size 크기
• Byte Ordering
  • Big Endian: LSB(Least Significant Byte) has highest address
  • Little Endian: LSB has lowest address