Topic 2: Computer Organization

Outline the architecture of the central processing unit (CPU) and the functions of the arithmetic logic unit (ALU) and the control unit (CU) and the registers within the CPU.

The CPU executes instructions of a computer program, such as arithmetic, logic, controlling, and input/output operations. The CPU contains the Control Unit (CU), Arithmetic Logic Unit (ALU), Memory Address Register (MAR), and Memory Data Register (MDR). The CU handles the loading of new commands into the CPU, decoding them, controls the retrieval of instructions from primary memory, and controls the sequence of execution of instructions.The ALU is responsible for arithmetic operations (add, subtract, multiply, divide) and logic operations (AND, OR, NOT). The MAR contains the RAM address of the instruction the CPU wants next and is connected to the address bus. The MDR holds data that will be written to or read from RAM and is connected to the data bus. Buses are connecting wires that connect the CPU to other devices, carrying instructions to/from components, and are normally built into the motherboard. The three most important buses are the data bus (links RAM to CPU via MDR), control bus (links RAM to CPU via CU), and memory bus (links RAM to CPU via MAR).

What is the function of the Control Unit (CU) in the CPU?

The CU handles the loading of new commands into the CPU, decoding them, controls the retrieval of instructions from primary memory, and controls the sequence of execution of instructions.

What is the function of the Arithmetic Logic Unit (ALU) in the CPU?

The ALU is responsible for arithmetic operations (add, subtract, multiply, divide) and logic operations (AND, OR, NOT).

What is the function of the Memory Address Register (MAR)?

The MAR contains the RAM address of the instruction the CPU wants next and is connected to the address bus.

What is the function of the Memory Data Register (MDR)?

The MDR holds data that will be written to or read from RAM and is connected to the data bus.

What are buses in the context of the CPU?

Buses are connecting wires that connect the CPU to other devices, carrying instructions to/from components, and are normally built into the motherboard.

What are the three most important buses and their functions?

The three most important buses are the data bus (links RAM to CPU via MDR), control bus (links RAM to CPU via CU), and memory bus (links RAM to CPU via MAR).

Describe primary memory.

• RAM ~ Random Access Memory

  • Volatile storage (data is NOT saved when computer is off)

  • Used to store everything (OS, programs, etc.) while computer is on

• ROM ~ Read-Only Memory

  • Non-volatile storage (persistent storage)

  • Often holds the computer’s BIOS (Basic Input/Output System) when computer first loads

Explain the use of cache memory.

Cache memory, also called cache, is a memory system that temporarily stores frequently used instructions and data for quicker processing by the CPU. Cache memory is used to store the information from RAM that is most actively used and accessed frequently, making the computer system run faster by reducing the need to access the slower main memory. Cache memory is nearer to the CPU than RAM, much faster than RAM, and more expensive than RAM. Cache memory is separated into L1 and L2 caches.

What are the differences between cache memory and RAM?

Cache memory is nearer to the CPU than RAM, much faster than RAM, and more expensive than RAM.

Explain the machine instruction cycle.

The machine instruction cycle refers to the fetch, decode, execute cycle where the ALU carries out calculations and logical decisions required by the program instructions that the CPU is processing.

1. Memory Address Register (MAR) contains address of instruction you want to fetch. MAR connected to address bus

2. Memory returns the fetched instruction down the data bus

3. Data bus is connected to Memory Data Register (MDR), so fetched data is in MDR2. Decode instruction in control unit

3. Execute instruction (data may be fetched from memory)

• MAR and MDR may be used again to fetch data from memory

4. Store results if necessary

• MAR and MDR may be used again to write data to memory

5. Repeat!

What are buses in the context of the CPU?

Buses are connecting wires that connect the CPU to other devices, carrying instructions to/from components. They are built into the motherboard.

What is the relationship between the MAR and MDR?

The MAR gives the address from which the data in the MDR will be read or to which it will be written.

What is the function of the Memory Data Register (MDR)?

The MDR is connected to the data bus and holds data that will be written to or read from RAM.

What are registers in the context of the CPU?

Registers are small, very fast circuits that store intermediate values from calculations or instructions inside the CPU.

What is the function of the Memory Address Register (MAR)?

The MAR contains the RAM address of the instruction the CPU wants next, is connected to the address bus, and contains a memory address to be used by the ALU.

Identify the need for persistent storage.

Data stays when power off

Describe the main functions of an operating system.

The five main functions are User Interface (UI), Memory Management, Peripheral Management, Multitasking, and Security. The UI provides the link between the user and the computer’s hardware. Types of UI include GUI (Graphical User Interface), CLI (Command Line Interface), NLI (Natural Language Interface), and MBI (Menu-Based Interface). Memory Management involves keeping track of storage devices, allocating memory (RAM) to programs, modifying memory locations, sorting data on disk drives and RAM for efficiency, organizing data into folders, and copying and deleting files. Peripheral Management involves coordinating with BIOS, using device drivers to interface with peripherals, and translating peripheral signals being received. Peripherals include devices like keyboard, mouse, and monitor. Multitasking works like a gatekeeper for the CPU, allowing access to concurrent programs based on priority and time, allocating CPU cycles, and ensuring the computer runs smoothly by giving each program a slice or turn to use the CPU. Security involves creating usernames and passwords, setting up user permissions (either inherited from parent or manually set), and managing file permissions for reading and writing.

What is the role of Security in an operating system?

Security involves creating usernames and passwords, setting up user permissions (either inherited from parent or manually set), and managing file permissions for reading and writing.

What is the role of Multitasking in an operating system?

Multitasking works like a gatekeeper for the CPU, allowing access to concurrent programs based on priority and time, allocating CPU cycles, and ensuring the computer runs smoothly by giving each program a slice or turn to use the CPU.

What is the role of Peripheral Management in an operating system?

Peripheral Management involves coordinating with BIOS, using device drivers to interface with peripherals, and translating peripheral signals being received. Peripherals include devices like keyboard, mouse, and monitor.

What is the role of Memory Management in an operating system?

Memory Management involves keeping track of storage devices, allocating memory (RAM) to programs, modifying memory locations, sorting data on disk drives and RAM for efficiency, organizing data into folders, and copying and deleting files.

What is the role of the User Interface (UI) in an operating system?

The UI provides the link between the user and the computer’s hardware. Types of UI include GUI (Graphical User Interface), CLI (Command Line Interface), NLI (Natural Language Interface), and MBI (Menu-Based Interface).

Outline the use of a range of application software.

word processors, spreadsheets, database management systems, email, web browsers, computer aided design (CAD) and graphic processing software

What is the use of word processors?

Word processors are used for creating, editing, formatting, and printing text documents. Examples include Microsoft Word and Google Docs.

What is the use of spreadsheets?

Spreadsheets are used for organizing, analyzing, and storing data in tabular form. They support calculations, graphing tools, and complex data analysis. Examples include Microsoft Excel and Google Sheets.

What is the use of Database Management Systems (DBMs)?

DBMs are used for storing, retrieving, and managing data in databases. They provide tools for data manipulation, query processing, and database administration. Examples include MySQL and Microsoft Access.

What is the use of email clients?

Email clients are used for sending, receiving, and managing email. They provide features like inbox organization, spam filtering, and contact management. Examples include Microsoft Outlook and Mozilla Thunderbird.

What is the use of web browsers?

Web browsers are used for accessing and viewing websites on the internet. They support web standards and allow users to navigate the web. Examples include Google Chrome, Mozilla Firefox, and Safari.

What is the use of Computer Aided Design (CAD) software?

CAD software is used for creating precise drawings and technical illustrations. It is widely used in engineering, architecture, and manufacturing for designing products and structures. Examples include AutoCAD and SolidWorks.

What is the use of graphics processing software?

Graphics processing software is used for creating, editing, and manipulating images and graphics. It supports tasks like photo editing, graphic design, and digital art creation. Examples include Adobe Photoshop and GIMP.

Identify common features of applications.

toolbars, menus, dialogue boxes, graphical user interface (GUI) component

What is the purpose of toolbars in applications?

Toolbars provide quick access to frequently used functions and tools within an application.

What is the role of menus in applications?

Menus organize and provide access to various commands and features of an application in a structured manner.

What are dialogue boxes used for in applications?

Dialogue boxes are used to prompt the user for input, provide information, or present options that need a response.

What are GUI components in applications?

GUI components include graphical elements like buttons, icons, checkboxes, and sliders that allow users to interact with the application.

bit

also known as a binary digit, is the smallest unit of data in computing and is represented by a 0 or a 1

byte

a group of 8 bits

Binary

a base 2 numeral system

Denary

 decimal, a base 10 numeral system

Hexadecimal

base 16 numeral system

AND

 returns 1 if both operands are 1; otherwise, it returns 0

OR

returns 1 if at least one of the operands is 1; otherwise, it returns 0

NOT

returns the complement of the operand

NAND

returns the complement of the AND operator

NOR

 returns the complement of the OR operator

XOR

returns 1 if only one of the operands is 1; otherwise, it returns 0