Fundamentals of computer systems Flashcards

Question

state some different types of management carried out by the operating system (5)

Answer 1

* allocation of processors * memory management * peripheral management * file management/secondary storage * power management

Answer 2

a resource/collection of program code to reduce the amount of programming required OR to provide access to subroutines OR to allow sharing of code across different programs

Answer 3

programs that performs tasks on the infrastructure of the computer. * driver manager : used to allow the operating system to communicate with an external devices * task monitor : used to display data relating to the system such as memory usage, processor usage, temperature * disk defragmenter : to reorganise files on hard drive for ease of access. to speed up your hard disk * file manager/backup manager : organises data firewall : used to control/prevent data from being transmitted or received

Answer 4

1. high level languages can run on different platforms 2. low level languages are platform specific 3. it is quicker to develop programs using high level languages 4. it is easier to maintain/debug 5. comments can be added to high level code

Answer 5

* bytecode is an intermediate code designed to be ran on a virtual machine OR bytecode is a type of machine code that will run on a software platform rather than a hardware platform (1) * this allows a high level language to be compiled into a format that can be run on any platform (1) * as long as the virtual machine is present (java and java virtual machine JVM) the bytecode is then compiled by the virtual machine at runtime into machine code that is platform specific (1) * this gives the appearance that compiling the program produces platform specific machine code, while actually allowing the compiled bytecode to be executed quickly across multiple platforms (1)

Answer 6

clock used to store the state of data OR memory data used to accept data OR allow data input OR change the internal state of the d-type flip-flop

Answer 7

* utility programs * operating system * library programs * translator

Answer 8

processor schedule memory management virtual memory management peripheral management file management interrupt handling power management user interface provision thread management

Answer 9

half adder result s is the sum of the two inputs adn c is the carry adding two binary digits

Answer 10

full adder for more than a single bit (half adder)

Answer 11

* malicious software * that enters a computer from the internet wihtout any explicit user interaction. * does not need to attatch itself to an existing application or file A small program that exploits a network security weakness (security hole) to replicate itself through computer networks

Answer 12

Real numbers can be thought of as points on an infinitely long number line All rational numbers are real numbers All irrational numbers are real numbers All natural numbers are real numbers pi is a real number All integers are real numbers

Answer 13

**Indicative repsonse** **Brute Force** * Caesar - Uses one common key for all characters. * Caesar - Easy to try all combinations of keys * Caesar - Very few possible double matches (where one ciphertext word could be converted to more than one plaintext word) * Vernam - It is impossible to use brute force to crack as each character uses a different key **Frequency analysis** * Caesar - most commonly found characters in the ciphertext message will match the most commonly found characters in the language * e.g. 'e', 'a', 't' in English are the most common characters * 'q' in English is almost always followed by 'u' * As the same key is used, once a match has been made some letters, the entire message will be compromised * Vernam - each character is encrypted using a different key and therefore frequency analysis is unhelpful * Vernam - even if one or two characters could be cracked with confidence, this would give no clue to the remainder of the message **Rules for key security** Assuming the key is: * truly random * only used once * kept secret by sender and receiver then the encryption is mathematically secure and cannot be decrypted even given infinite time and infinite ciphertext, whereas this is not true of the Caesar cipher.

Answer 14

Similarity (1) * both programs will be the same length and have the same number of instructions Difference (1) * the machine code program will be represented in binary * the assembly language program will be presented using ASCII/Unicode

Answer 15

* Instructions are carried out in a specified order * The language described how to solve the problem SIS

Answer 16

A utility program is used to maintain/optimise a computer system (1) Examples: * Anti-malware * Firewall * Disk defragmenter * Disk cleanup * System monitor * Backup Manager * etc *

Answer 17

A library program is a collec tion of program code (aka a resource) that can be accessed by other programs (1) Examples: * Math library * Random number library * GUI library

Answer 18

A translator is used to translate high-level language / assembly language source code into machine code (for execution) (1) Examples: (1) * assembler * compiler * interpreter

Answer 19

Role of the OS: to hude the complexity of the hardware from the user (1) Key functions (any six from) (6) * Processor scheduling OR allocation of processors * Memory management OR allocation or RAM * Virtual memory management OR allocation of VM * Peripheral management OR I/O management * File management OR backing store management OR secondary storage management * Interrupt handling * Power management OR battery management * User interface provision * Thread management (in the context of CPU/processor scheduling)

Answer 20

Need: (2) * The high-level language source code cannot directly be understood/executed by a processor (1) * Must be translated into machine code in order to be executed (1) Steps: Any three from (3) * Each instrcution is checked for syntax errors (1) * Each instruction is translated into machine code instructions (1) * Use the instruction set specific to the system/platform/processor (1) * One high-level language instruction my be translated into several machine code instructions (1) For an interpreter; each instruction is then executed by the process For a compiler; each instruction is then stored in an object code / machine code / bytecode file (1)

Answer 21

* Easier/quicker to read/write (1) as HLL is closer to natural language / english (1) * Less likely to make mistakes (1) as machine code look very similar (1) * Logic in HLL is easier to folow (1) due to the use of structured statements OR daa structures of comments (1) * Can be run on different platforms (1) as machine code is specific to one instruction set OR platform (1)

Answer 22

* Source code is needed to execute the program so every machine that runs the program needs the source code. This means that anyone can can view/edit/improve/maintain the algorithms/program code. The program can be updated more easily as the form and structure of the data may change over time. * The program will not need to be translated separately for each platform before it is shared and the program will work on any platform for which an interpreter is available. * Debugging will be easier as the program will halt at the exact point in the program where an error is detected. * Some programming languages are restricted to either a compiler or an interpreter.

Answer 23

**Reading mechanism** * (Low power beam of) laser / light is shone at disk NE. implication because it is reflected * Light is focussed on spot on track * (Some) light is reflected back from disk * Amount of light reflected back is measured // light sensor detects reflection * Disc spins at constant linear velocity // zoned constant linear velocity // variable (angular) velocity * A. variable speed * R. constant speed **How data is represented** * Data is stored on one/spiral track * A. data is read in a spiral * Continuation of land/pit reflects light whereas transition between land and pit scatters light * A. land reflects light whereas pits scatter light/do not reflect light or vice-versa * A. “bump” for “land” * Transition between land and pit indicates a 1 and continuation of land/pit represents 0 * A. land represents 1, pit 0 or vice-versa * A. reflection represents 1, no reflection 0 or vice-versa * A. “bump” for “land” or other wording which clearly reflects nature of pits and lands

Answer 24

* Flash drives can have a higher (storage) capacity; * Flash drives have faster access/read/write times; * No drive is required to use a flash drive // flash drive and medium are integrated; * Flash drives can be reused; * Flash drives are more compact; * Flash drives not damaged by scratches;

Answer 25

* The solid-state drive operates by trapping electrons in a wafer of semiconducting material * The electrons and their electric charge remain trapped even when electric power is removed; i.e. SSD is non-votalite storage * The sites where these electrons are trapped are organised in a grid * The entire grid layout is known as a **block** * Individial **rows** that mke up the grid are a **page** * Unlike magnetic disk drives, solid-state drives contain no moving parts. This means that solid sate dries can operate faster * The technology used is NAND flash memory which is a type of EEPROM (Electrically Erasable Programmable Read Only Memory). * An SSD is a block-oriented storage device which has to erase a block first in order to rewrite it because NAND flash memory can't overwrite existing data. Erasing a block means 'untrapping' electrons. * Requires an oboard controller which has an embedded microprocessor with RAM buffer to perform reading and writing to the SSD. * SSD blocks can be programmed for only a limited amount of time before they become unreliable. This is know as write-endurance. * The lessen the effect of write-endurance, the controller uses a technique called wear-levelling; it makes sure that all the drives memory chips are used, cell by call, before the first cell is written on again.