Topic 2: Computer Organization

CPU (Central Processing Unit)

Processes all instructions as binary code; code is executed here. Contains the ALU, CU, MAR and MDR

ALU (Arithmetic Logic Unit)

Performs all the basic arithmetic, logical, or input/output operations.

CU (Control Unit)

Is responsible for providing the ALU with the data that needs to be processed as well as processing instructions

MAR (Memory Address Register)

 

Holds the memory addresses of the data to be used by the ALU, so that the ALU can fetch the content and process it accordingly. The MAR may also hold the memory address where the data needs to be stored.

MDR (Memory Data Register)

The MDR holds the data that is to be used by the ALU and then saved to the RAM.

What are the two parts of the primary memory?

RAM and ROM

RAM (Random Access Memory)

• “Short-term memory”

• Consists of units of data, each with a hexadecimal address

• Volatile - data lost when electricity is cut off (when computer is turned off) (non-persistent storage)

ROM (Read-Only Memory)

• Used to store permanent instructions necessary to boot computer

• Holds BIOS (Basic Input Output System)

• Instructions written in factory

• Non-volatile (data persists without electricity)

Cache

• Stores frequently used instructions from RAM

• Processor checks cache first

• Increases speed of FDE cycle

• Cache memory more expensive, but faster

  • Closer to CPU than RAM, which contributes to speed

Secondary Memory

• Hard Drive, Removable Storage (USB Drive, CDs)

• “Long-term Memory”

• Persistent storage

• Holds all data not currently in use

• Data for running programs transferred from secondary to primary memory

• Slower and cheaper than primary

• Not directly connected to CPU

• Much larger amounts

Virtual Memory

• When primary memory overloaded, data sent to secondary

• Slower

• Temporary

• Returned to primary memory as needed

• Stored in units called “pages”

What are the steps in the fundamental operation of a computer?

1. Input (read) values

2. Processing/execution of values (eg calculate, decode, fetch, delete, evaluate, sort,

   transfer, transmit)

3. Output data

4. Compare values

5. Store values in memory or secondary storage

What is the difference between fundamental and complex operation of a computer?

Complex operation requires a number of other, fundamental operations in order to reach the final result.

What is an OS?

Operating system. A set of software that controls computer’s hardware and resources and provides services for computer programs.

What are the five roles of an OS?

1. User interface

2. Memory Management

3. Peripheral Management

4. Multitasking

5. Security

What are the four types of UI?

• GUI (Graphical User Interface) - menus, point and click

• CLI (Command Line Interface) - type in commands

• NLI (Natural Language Interface) - speak to computer (Siri)

• MBI (Menu Based Interface) - Like CLI, but no commands, only menu option

What is involved in memory management?

• Keep track of storage devices (HDD, Flash Drive)

• Allocate memory (RAM) to programs

• Modify memory locations

• Sort data on disk drives and RAM for efficiency

• Organize data into folders

  • Copy and delete files

What is involved in peripherals management?

• Peripherals - keyboard, mouse, monitor, etc.

• Coordinate with BIOS (basic input/output system)

• Use device drivers to interface with peripherals

• Device drives translate peripheral signal

What does it mean when an OS does multitasking?

• Allocates CPU cycles to concurrent programs based on priority and time

• Each program given a slice of time, or a “turn” to use CPU

• Slices vary in length of time

What security does the OS provide?

• Username and password

• User permissions

  • File permissions for reading and writing

What are the features of a programming language?

• Consistent grammar

• Consistent syntax

• Provide a way to define basic data types and operations on those types (ability to write functions/procedures)

• Provide ability of input and output handling

• Provide some kind of loop that can be stopped / conditional statement / branching (conditional and unconditional branching)

• Has to run on/be able to be processed by a computer (ie it must have a compiler/interpreter)

Differences between high level and low level programming languages

• Abstraction - High-level languages provide greater abstraction from the hardware, using human-readable syntax whereas low-level languages often require direct interaction with hardware specifics, such as memory addresses and registers

• Ease of Use - High-level languages are generally easier to learn and use because they are closer to natural human language and automate many programming tasks

• Performance and Control - Low-level languages offer finer control over system resources and potentially faster performance due to their proximity to machine code

What is a compiler?

translates code written in a high-level programming language into machine code (object code) that a computer's processor can execute

What is a interpreter?

Directly executes instructions written in a programming language (line-by-line) without requiring them to be first compiled into machine code

Differences between higher level programming languages?

• Method of translation - whether by compiler or interpreter (or both)

• Loosely/strongly typed - refers to whether data types are specified

• Compatibility with different environments - Java with virtual

• machine can run on all OSes, but some languages are OS specific

• Syntax differences

Application Software

• Word Processors (Word)

• Spreadsheets (Excel)

• Database Management System (DBMS) (MS Access)

• Email Client (Outlook)

• Web Browser (Google Chrome)

• Computer Aided Design (CAD)

• Graphic Processing Software (Photoshop)

Data storage units

• 1byte=8bits

• 1 kilobyte = 1024 bytes

• 1 megabyte = 1024 kilobytes

• 1 gigabyte = 1024 megabytes

• 1 terabyte = 1024 gigabytes

ASCII vs Unicode for displaying text

ASCII

• Uses 8 bits for each character

• 7 bits used for each character, 1 bit is parity bit

• 2^7 or 128 possible characters

• Lower case, capitals, numbers, symbols, spaces, punctuation included

Unicode

• Used to represent multiple languages

• More bits, so more characters can be represented

• UTF-8 → 8 bits, UTF-16 → 16 bits, UTF-32→32 bits

What represents true in a truth table and what represents false?

True is represented by 1, and false is represented by 0.

Logic Gates: Not

Flips the value from true to false or vice versa.

Logic Gates: And

Only returns true if both values are true.

Logic gates: Or

Returns true if there is one true.

Logic Gates: Nand

Returns not and.

Logic gates: Nor

Returns not or.

Logic gates: xor

Returns the or value if both values are different; otherwise returns false.