CPU Components

Components in a CPU

General purpose Registers

  • Register
    • A synonym for memory in computer science
  • General purpose reigster
    • A memory cell
  • Each general purpose register has a unique name
  • It is used to 
    • store (and recall) intermediate result of complex computations

Arithmetic and Logic Unit (ALU)

  • It is a complex electrical circuit that can perform Mathematical (+,-,x,/) and logical operation (<, <=, >, >=, and, or)
  • The output (result) of the computation (obtained by the ALU) is often stored in a general purpose register

Instruction Register (IR)

  • Contains the current instruction being executed by the CPU
  • The CPU will perform the operation indicated by the instruction code contained in the instruction register

Program Counter (PC)

  • The program counter is a register (memory cell)!
  • This register contains the address (location in memory) of the next instruction after the CPU finishes executing the current instruction in the instruction register
  • The value in the program counter will be increased after the CPU finishes executing one instruction

Processor Status Register (PSR)

  • This register contains the various information about the CPU.
  • Among the information contained in the PSR is
    • The result of a comparison operation
  • When the CPU compares 2 numbers a and a and b,  the outcome of the comparison is stored in the PSR
  • The outcome of a compare operation will allow the CPU to determine the following fact between a and b.


[1] http://www.mathcs.emory.edu/~cheung/Courses/170/Syllabus/01/intro-computer2.html

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