IB Comp. Sci - Paper 1, Topic 2

CPU (2.1.1)

(Central Processing Unit) The key component of a computer system, contains the circuitry necessary to fetch, decode, and execute program instructions from and to main memory (RAM)

Function of the ALU (2.1.1)

(Arithmetic Logic Unit) Part of the CPU that does all the arithmetic (+/-) and logical (AND/OR) calculations; Sometimes known as the ‘core.’ - computers with dual core technology can have two ALUs to process two calculations simultaneously

Functions of the CU (2.1.1)

(Control Unit) Handles the loading of two commands into the CPU and the decoding of those commands; Directs data flow and the operation of the ALU

Registers (2.1.1)

Small, very fast circuits that store intermediate values from calculations or instructions inside the CPU; Most important registers include MAR, MDR, & accumulator* (*= not accessed in this course)

MAR (2.1.1)

(Memory Address Register) connected to the address bus, contains a memory address, sole function is to contain the RAM address of the instruction the CPU wants next

MDR (2.1.1)

(Memory Data Register) connected to the data bus, holds data that will be written to the RAM or that was read from the RAM

Relationship between MDR & MAR (2.1.1)

MAR gives the address the data of the MDR will be read from or written to

Busses (2.1.1)

The connecting wires that connect the CPU to other devices, carrying instructions to/from components; Normally built into the motherboard.

Three most important busses (2.1.1)

Data bus (links RAM to CPU via MDR), Control bus (links RAM to CPU via CU), & Memory bus (links RAM to CPU via MAR)

RAM (2.1.2)

(Random Access Memory) AKA primary memory; contains the data and instructions the computer has loaded since the starting up and everything the user has opened/loaded; is volatile = loses its contents if power is lost; had special link to the CPU

ROM (2.1.2)

(Read Only Memory) Non-volatile = does not lose its contents if power is lost; stores the BIOS

BIOS (2.1.2)

(Basic Input Output System) a small program that allows computer to know what to do to find the operating system to ‘boot’ the computer after power is restored

Cache (2.1.3)

A small, high-speed memory inside the CPU used to hold frequently used data, so that the CPU needs to access the much slower RAM less frequently

The Fetch-Execute Cycle (2.1.4)

The basic operation of a computer; computer fetches the information from its memory and executes it; done repeatedly from when computer is booted up to shutting down

Step 1: Fetching the instruction (2.1.4)

CPU fetches this from the main memory (RAM) and stores it in the CPU temporary memory, called the registers

Step 2: Decoding the instruction (2.1.4)

CPU needs to understand the instruction to execute it

Step 3: Executing the instruction (2.1.4)

CPU carries out the action that is needed

Why do we need storage? (2.1.5)

Describe the functions of an operating system (2.1.6)

A. Provides a user interface, B. Does memory management, C. Does peripheral management, D. Allows multi-tasking, E. Provides security

A. Provides a user interface (2.1.6)

OS has to provide a link between the user and the computer hardware. Types of user interfaces include: Graphical User Interfaces (GUI) that have menus and icons, Command Line Interfaces (CLI) where the user types in codes, Natural Language Interface (NLIs) where the user speaks to the interface, Menu Based Interface (MBIs) which gives the user a selection of options

B. Memory Management (2.1.6)

Done by keeping track of storage devices (like HDD) and controlling which application has access to which area of memory (RAM); OS allows users to organize files in folders as well as to copy and delete files

C. Peripheral Management (2.1.6)

Keyboard, mouse, monitor, and printers are controlled through device drivers; A device driver is a software program which allows hardware devices to be used by the OS. They act as translators between the devices and the computer system

D. Multi-tasking (2.1.6)

The OS coordinates the workings of different programs by allocating the CPU time between different programs based on time and priority of the software application; Each task running is given a slice of time, or turn on the CPU; Each task has to wait its turn unless it is given a higher priority by the OS in which case it gets more or longer time slices

E. Security (2.1.6)

OS prevents unauthorized access; ensures the security of systems through usernames and passwords; protects files from other users reading or writing files

Common application software (2.1.7)

Word processors, spreadsheets, Database Management Systems (DBMS), email clients, web browsers, Computer Aided Design (CAD), Graphic Processing Software

Word Processor (2.1.7)

A program for storing, manipulating, and formatting text from a keyboard and providing a printout

Spreadsheet (2.17)

A program in which data is arranged in the rows and columns of a grid and can be manipulated and used in calculations

Database Management System (2.1.7)

A system software for creating and managing databases. Provides users and programmers with a systematic way to create, retrieve, update, and manage data

Email clients (2.1.7)

A computer program used to access and mange a user’s email

Web browser (2.1.7)

A software application used for retrieving, presenting, and transversing information resources on the World Wide Web

Computer Aided Design (CAD) (2.1.7)

Programs that use computer systems to assist in the creation, modification, analysis, or optimization of a design

Graphic Processing Software (2.1.7)

A program or collection of programs that enable a person to manipulate visual images on a computer

Common features of most programs (2.1.8)

Toolbars, menus, dialogue boxes, GUI components

Bit (2.1.9)

Binary digit; smallest unit of dating in computing; represented by a 0 or 1

Byte (2.1.9)

Group of 8 bits

Binary (2.1.9)

the format in which numbers are transmitted and calculated in a computer system; referred to as BASE-2 numbering

Denary/decimal (2.1.9)

A numbering system with 10 symbols: 0123456789; referred to as BASE-10 numbering

Hexadecimal (2.1.9)

A numbering system with 16 symbols: 0123456789ABCDEF; referred to as BASE-16 numbering; used to represent very large numbers quickly

What is logic? (2.1.11)

How a machine will solve problems

Truth table (2.1.12)

A mathematical table that shows all possible outcomes that could occur from all possible scenarios that are considered factual