Libraries (cont.)

Two options to load dynamic libraries:

1. Take the DLL file and load it right away
   • load - take dll file and put it in RAM memory, so it is accessible by running programs
   • loading is time-consuming because we need to copy from hard disk
2. only load into RAM when it is needed ("lazy loading")
   • allows us to start the program faster, more memory efficient
   • BUT, can cause significant delay the first time the DLL is used in the program

Different kinds of builds

Debug build:

• Compiler makes it easy to debug program
• Slower, less efficient
• Compiler adds runtime checks, additional symbols
• Larger executable
• Makes it easier to find problems
• Type of build that is usually done when writing code

Release build:

• As fast as possible
• As small as possible
• Compiler optimizations enabled typically
• Ballpark estimate for speedup compared to debug build, with compiler optimizations - around 10x faster

CPU design

Relevant reminder items for this section:

• Logic gates (input and output)
  • Hardware that implements boolean functions
• Flip-flops and latches
  • not discussed in this couse, but are used to store 0 or 1 - trap the bit value
  • used to create memory

We use flip-flops to construct registers because they are fast:

• for example, 32-bit registers have 32 flip-flops

Registers and Register File

• 32 wires go into the register
  • inputs to flip-flops to deliver new values
• "write enable" - register is only updated if this input is 1, otherwise it ignores new values
• also, 32 outputs, that always show the outputs of the register (values currently stored)