Computer Architecture

A computer system consists of the physical computer, called the hardware, and the programs, called the software, that instruct the machine. The term architecture refers to the way the computer hardware is organized. There are several variations but basically the computer hardware is organized into components based on their function. The two primary components are the Central Processing Unit (CPU) which does the processing of data (executing instructions) and main memory which holds the data and instructions the CPU is currently using. These two units work together very closely (details below!) to do the "computing." This organization is much the same as the organization outlined by John von Neumann over 50 years ago and is often called the von Neumann architecture. One key aspect of this architecture is that the programs are actually stored in the memory of the computer just as other data.

Of course, in addition to the primary components to do the computing, the computer needs means of communicating with the user so it has input/output devices and there needs to be a way to store programs and data long term. The main hardware components and their functions are summarized below.

The Hardware Components of a Computer

The CPU and main memory are realized in chips mounted on a circuit board called the motherboard or system board. The different components are connected by a group of wires called a bus. Data, instructions, and control signals travel along the bus as the various components communicate with each other.

The above description gives a general overview of basic computer hardware. There are many variations in modern computers designed to speed the computer up. Many modern computers are multiprocessors; that is, they have more than one CPU. Most modern computers have an additional type of memory called cache. Cache is an intermediate form of memory designed to speed up access to data. There is RAM cache which is used to speed up the CPU's access to data in RAM and disk cache which is used to speed up access to data on disk.

Review and Study Questions

  1. What are the two primary hardware components of a computer and how do they interact?
  2. What are the two major components within the CPU and what is the role of each?
  3. The CPU also contains registers. What are registers?
  4. What is the role of each of the following special registers in the Fetch/Execute Cycle: Program Counter, Instruction Register?
  5. The Fetch-Execute Cycle is basically "how the computer works" - it is often called the "foundation of computer processing." Describe the Fetch-Execute (Fetch-Decode-Execute) cycle in detail (including what is being fetched, how the Control Unit knows how to find what is being fetched, and so on).
  6. What are the differences between RAM and ROM?
  7. What does volatile mean?
  8. What is the difference in the ROLE of main memory and that of auxiliary memory?
  9. How is data located in main memory?
  10. What is a bus?
  11. List at least 3 specific auxiliary storage devices other than hard disks.
  12. List at least 4 different input devices.
  13. List at least 3 output devices.