Skip to main content

Computer Architecture Study Guide

Computer Architecture Study Guide

By Vangie Beal

Webopedia Study GuideComputer architecture provides an introduction to system design basics for most computer science students. This Webopedia  study guide describes the different parts of a computer system and their relations.
Students are typically expected to know the architecture of the CPU and the primary CPU components, the role of primary memory and differences between RAM and ROM. Other topics of study include the purpose of cache memory, the machine instruction cycle, and the role secondary memory plays in computer architecture.
Public Safety Device Trends

Computer Architecture Guide Checklist

Tweet This Study Guide!
Webopedia study guides offer quick facts to help students prepare for computer science courses. Did you find this guide useful? Click to share it with friends and classmates on Twitter.

1. Getting Started: Key Terms to Know

The following definitions will help you better understand modern computer architecture:

2. The Architecture of the Central Processing Unit (CPU)

The central processing unit (CPU) is where most calculations take place. It is an internal component of the computer that is often referred to as the "brains" of the computer.  Modern CPUs are small and square and contain multiple metallic connectors or pins on the underside. The CPU is inserted directly into a CPU socket, pin side down, on the motherboard. The CPU is the most important element of a computer system in terms of computing power.

3. Primary Components of a CPU

The Arithmetic Logic Unit

The arithmetic logic unit (ALU) performs arithmetic and logical operations. It is where data is held temporarily and where calculations take place.

The Control Unit

The control unit (CU) controls and interprets the execution of instructions It extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.

4. Diagram: The Relationship Between the Elements

The following diagram showing the relationship between the elements of the CPU, input and output, and storage.
CPU Diagram

5. Primary Memory Explained

There are two types of physical memory: primary and secondary memory. Primary memory is volatile memory. Secondary memory (secondary storage) is non-volatile.
Recommended Reading: Webopedia's volatile memory and non-volatile memory definitions.
The main functions of primary memory  (also called main memory or primary storage) is to execute program code and store temporary data. Primary memory is the memory that the processor accesses first. The memory is on chips located on the motherboard. The primary memory  stores applications to run the operating system (OS), the user interface and installed software utilities.
The computer can manipulate only the data that is in main memory. Every program executed and every file accessed must be copied from a storage device into main memory. The amount of main memory in a computer system determines how many programs can be executed at one time and how much data can be readily available to a program.
Did You Know...?  A small program (called a boot loader or bootstrap loader) is stored in primary memory. It loads the operating system into the computer's memory when the system is booted and the program also starts the operating system. This process is known as "booting up" the computer.

6. Primary Memory: RAM and ROM

Examples of primary memory include RAM and ROM.

What is RAM?

Random access memory (RAM) is a type of volatile memory and is the most common type of memory found in computers and other devices, such as printers. RAM requires a flow of electricity to retain data (e.g., the computer is powered on).

What is ROM?

Read-only memory (ROM) is a type of non-volatile memory and is computer memory on which data has been prerecorded. ROM will retain data without the flow of electricity (e.g., when the computer is powered off).

7. The Role of Secondary Memory

Secondary memory (also called auxiliary memory) is storage devices: hard drives, solid state drives, removable storage media -- including flash drives and DVDs.
Secondary memory is not accessed directly by the CPU as it is with primary memory. Instead, data from secondary memory is loaded into RAM then sent to the processor. It transfers the requested data to an intermediate area in primary storage. While secondary memory is much slower than primary memory, it offers greater storage capacity.

8. Persistent Storage

Persistent storage (storage that doesn't lose its data after it loses its power supply) is extremely important in a computer system. It is needed to store data in a non-volatile device during and after the running of a program to keep files and data for later use. The hard disk drive is a common example of persistent storage.

9. The Purpose of Cache Memory

Cache memory (also called CPU cache) is a high-speed storage mechanism that is a reserved section of main memory or an independent high-speed storage device. The CPU cache reduces the time required to access data from the main memory. Modern CPUs have different independent caches, such as instruction and data caches.
There are two types of caching commonly used in computer systems: memory caching and disk caching.

What is Memory Cache?

Memory cache, sometimes called RAM cache, is a portion of memory made of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory. Memory caching is effective because most programs access the same data or instructions over and over.

What is Disk Caching?

Disk caching works under the same principle as memory caching, but instead of using high-speed SRAM, a disk cache uses conventional main memory. Disk caching can dramatically improve the performance of applications, because accessing a byte of data in RAM can be thousands of times faster than accessing a byte on a hard disk.

10. The Machine Instruction Cycle

The instruction cycle refers to the time period during which one instruction is fetched from memory and executed when a computer is given an instruction in machine language. The CPU carries out the following four stages of an instruction cycle:
1. Fetch the instruction from memory. This step brings the instruction into the instruction register, a circuit that holds the instruction so that it can be decoded and executed.
2. Decode the instruction. Mathematical and logical operations used in reference to data.
3. Read the effective address from memory if the instruction has an indirect address.
4. Execute the instruction. This combines all steps.
Note: Steps 1 and 2 are called the fetch cycle and are the same for each instruction. Steps 3 and 4 are called theexecute cycle and will change with each instruction.
Recommended Reading: Webopedia's instruction cycle definition.

Additional Resources for Learning Computer Architecture

Courtesy of Carnegie Mellon Computer Architecture, the following lecture covers the introduction and basics of computer architecture.

Popular posts from this blog

Hidden Wiki

Welcome to The Hidden WikiNew hidden wiki url 2015 http://zqktlwi4fecvo6ri.onion Add it to bookmarks and spread it!!!
Editor's picks Bored? Pick a random page from the article index and replace one of these slots with it.
The Matrix - Very nice to read. How to Exit the Matrix - Learn how to Protect yourself and your rights, online and off. Verifying PGP signatures - A short and simple how-to guide. In Praise Of Hawala - Anonymous informal value transfer system. Volunteer Here are five different things that you can help us out with.
Plunder other hidden service lists for links and place them here! File the SnapBBSIndex links wherever they go. Set external links to HTTPS where available, good certificate, and same content. Care to start recording onionland's history? Check out Onionland's Museum Perform Dead Services Duties. Introduction - Clearnet search engine for Tor Hidden Services (allows you to add new sites to its database). DuckDuckGo - A Hidden S…


Good News [May 08, 2015]: IDM developers got smarter, but the crackers are always a step ahead. Follow this article and send an email to if you are desperate. I can NOT post any crack here for legal reasons. Happy Downloading with IDM. ;) *********** first tip is to use latest crack for idm from idm universal web crack and make sure u are using all latest vers I am sure many of us are too much dependent on Internet Download Manager a.k.a. IDM. The main reason didn’t permanently switch to linux was IDM. I mainly use it for batch downloading and download streaming videos. Till yesterday, IDM was working fine with me (of course with fake serial numbers, keygen, crack, patch etc. which could be found with little effort). But few days ago, with the latest update version 6.18 build 7 (released on Nov 09, 2013) Internet Download Manager was literally had a breakthrough and crushed all the serial numbers, …

DoubleAgent Attack Turns Your Antivirus Into Malware And Hijacks Your PC

Short Bytes: Cybellum security researchers have uncovered a new attack mechanism that can be used to take control of your antivirus and turn it into a malware. Called DoubleAgent, this attack exploits an old and undocumented vulnerability in Windows operating system. This Zero Day code injection technique affects all major antivirus vendors and has the power to hijack permissions. The security researchers from Cybellum have found a new technique that can be used by the cybercriminals to hijack your computer by injecting malicious code. This new Zero-Day attack can be used to take full control over all the major antivirus software. Instead of hiding from the antivirus, this attack takes control of the antivirus itself. Called DoubleAgent, this attack makes use of a 15-year-old legitimate feature of Windows (read vulnerability)–that’s why it can’t be patched. It affects all versions of Microsoft Windows. Cybellum blog mentions that this flaw is still unpatched by most antivirus v…