Yaolin Ge

Computer Systems A Programmer's Perspective

#systems#csharp

In C#, bool uses 1 byte (not 1 bit) due to memory alignment. To store multiple flags efficiently, use bit masking:


byte flags = 0b_0000_1010; // 8 flags in 1 byte
bool flag2 = (flags & (1 << 1)) != 0; // check 2nd flag
bool flagN = (flags & (1 << N)) != 0; // check N-th flag, 0 <= N < 8

Chapter 3: Machine-Level Representation of Programs

  • Each memory address is 8 bytes (64 bits) in modern systems.
  • A 32-bit machine can only m ake use of around 4GB (2^32 bytes) of memory.
  • A 64-bit machine can address up to 16 exabytes (264 bytes), but practically it is 248 bytes (256 TB) due to OS limitations. Given the development of AI and demand for large context windows. It is needed to use all 64 bits for memory addressing.