Instruction Sets

Question 1

What is a macro?

Answer 1

A macro in computer science is a rule or pattern that specifies how a certain input should be mapped to a replacement output. Applying a macro to an input is macro expansion. The input and output may be a sequence of lexical tokens or characters or a syntax tree.

In c these are indicated by a #.

The preprocessor deals with macros either linking files or or replacing macros with their definitions.

Question 2

What are the control transfer instructions?

Answer 2

Jump Instruction and Branch Insrtuctions.

Question 3

What is a register in a normal desktop?

Answer 3

Register: Static RAM (SRAM) cells in the CPU.
Fundamentally just transistor-switching.

Question 4

What is memory in a normal desktop computer?

Answer 4

Memory: Dynamic RAM (DRAM) cells far away from CPU
Much more dense, but relies on capacitor charge/discharge (which requires refreshing via a clock signal).

Question 5

What is the motivation for load and store instructions?

Answer 5

Main memory is slower to access than
CPU registers. Most instructions operate on CPU
registers, and some instructions load data from
memory (in register-register architectures. . . )

Question 6

Why use immediate instructions?

Answer 6

Because data is part of the instruction, saves requirements for load/store

Question 7

More Addresses per Instruction VS Less addresses per instruction

Answer 7

• More addresses:
  
  • More complex (powerful?) instructions.
  • More registers (less data transfer)
  • Fewer instructions overall per program
• Fewer addresses:
  
  • Faster fetch/execution of instructions

Question 8

What types of ISAs are there?

Answer 8

• Accumulator
• Stack
• Register-memory
• Register-register load-
/store
• Memory-memory (old
machines)