Computer Systems

Question 1

Define Hardware

Answer 1

• Physical components of the computer system (you can touch it)

Question 2

Define Software

Answer 2

• Program code, sequences of instructions which are executed in order to perform a task (non-physical)

Question 3

Hardware examples

Answer 3

• Monitor
• Processor
• Graphics
• Webcam

Question 4

Software examples

Answer 4

• Word Processor
• Web Browser
• Image editor
• Video editor

Question 5

Examples of both software and hardware

Answer 5

• Wireless router
• Wireless keyboard

Question 6

Application Software

Answer 6

• programs that run to complete a specific task for the user e.g. Word, Powerpoint

Question 7

What does a device driver do?

Answer 7

• Allows the device to communicate with the OS

Question 8

Operating system role

Answer 8

• System software that allows control of the computer while hiding complexities using a virtual machine
• Manages/controls resources, memory, processor scheduling and interrupts
  e.g. Windows, Ios, Linux

Question 9

Translators role

Answer 9

• Translate between different programming languages (high/low)
  e.g. VS(Compiler), Python(Interpreter)

Question 10

Utility Programs role

Answer 10

• System software to complete housekeeping tasks
  -Data backup, defragmenting, compression and encryption
  e.g. Disk clean-up, antivirus, firewall, task manager

Question 11

Library programs role

Answer 11

• Useful functions frequently used by a program, programmers import them within their code to simplify the process
  e.g. NetCore, NetFramework, OpenSSL

Question 12

What is the purpose of the operating system? (In reference to the user?

Answer 12

• The purpose of an operating system is to hide the complexities of hardware from the user (providing a VM), and manage said hardware.

Question 13

What types of management can the operating system perform?

Answer 13

(detail explain these if a question comes up)
- Memory management
- Resource management
- Security management
- Command Interpreter
- File management
- Input/Output management

Question 14

What types of resource management can the OS perform?

Answer 14

• Allocates space on a storage device
• Moves data into/out of RAM
• Allocates memory/RAM to processes
• Install + Manage users on a network

Question 15

What are Low level languages?

Answer 15

• Languages directly manipulated by the processor
• Require a lot of work to code and – Very error prone.
  e.g. Machine Code and Assembly language

Question 16

What are High-level languages?

Answer 16

• Allow for instructions to be communicated much easier
• Have to be translated before the computer can read them.

Question 17

What is Assembly Language, and what are the key mnemonics?

Answer 17

hash .# denotes a denary number

• Uses mnemonics to simplify the process of computer programming and make it easier
  LDR - Load
  STR - Store
  ADD - Add
  INP - Input
  HALT - End
• Read backwards to indicate where objects are stored

Question 18

Machine Code

Answer 18

• Language the computer directly reads, e.g. binary

Question 19

High vs Low Level Languages

(Machine Code, Assembly and HL languages)

Answer 19

LL Machine Code;
- Not portable
- difficult for humans to understand
- difficult to spot errors
- directly executed by processors

LL Assembly Language;
- Processor specific
- Mnemonics slightly easier, debugging slightly easier than MC but harder than HL Languages,
- Assembler must be used, quick translation due to 1 to 1 correlation

HL Languages;
- Portable, non specific, easy for humans to understand and debug (named variables + indentation).
- A compiler or interpreter must be used to translate source code into object code before it can be executed. This can be time consuming

Question 20

Machine code positives and negatives?

Answer 20

Positives;
- Programmers are not restricted
- No translator is needed
- Useful for embedded systems as it is faster

Negatives;
- Difficult to read, work with and understand
- Operation codes and memory addresses must be remembered
- Very difficult to amend/locate errors

Question 21

What are assemblers?

translation

Answer 21

Assembly to machine code;

• Quick and straightforward, due to 1 to 1 relationship;
• Platform specific, each processor instruction set requires its own assembler;

Question 22

What are compilers?

translation

Answer 22

High level language to machine code;
- Taken as source code, checked for errors;
- Translated all at once, once compiled, can run without any other software (not the case for interpreters);

Question 23

What are interpreters?

translation

Answer 23

High level language to machine code;
- line by line error checking
- Stops if error is found
- SC and interpreter must be present, making this method vulnerable

Question 24

Compilers versus Interpreters

Answer 24

Compiler;

• Translation begins immediately;
• Entire source code is translated at once;
• No need for source code or compiler to be present when translated code is executed;
• Protects the source code from extraction

Interpreter;

• Checks source code for errors line-by-line before translating;
• Each line is translated sequentially (after error checking);
• source code + Interpreter must be present when the program is executed (vulnerable);
• Offers little protection of the source code ;

Question 25

What is an intermediate language?

Answer 25

- Some compilers first translate into an intermediate language commonly known as **byte code**. - Byte Code allows the code to be used on a variety of processors due to being independent (working on any system)

Question 26

truth table

Answer 26

- shows every possible combination of inputs and corresponding outputs for a logic gate or circuit

Question 27

NOT gate Boolean Logic Symbol

Answer 27

¯A | over the A

Question 28

AND gate Boolean Logic Symbol

Answer 28

A.B

Question 29

OR gate Boolean Logic Symbol

Answer 29

A + B

Question 30

XOR gate boolean logic symbol

Answer 30

A ⊕ B

Question 31

Why should you try to use as few gates as possible in a circuit?

Answer 31

- Less power used by the processor - Faster - Less heat and lower cost

Question 32

Adders

Answer 32

- A logic circuit that can be used to add Boolean values together

Question 33

Half Adder

Answer 33

- 2 inputs, 2 outputs, 2 logic gates (XOR, AND)

Question 34

Full Adder

Answer 34

- 3 inputs, 2 outputs, Used in most digital circuits

Question 35

Boolean Algebra order of precedence:

Answer 35

1. () 2. NOT 3. AND 4. OR

Question 36

De Morgan's Law

Answer 36

—> Break the line, change the sign

Question 37

Boolean Identities

Answer 37

A.0 = 0 Any value and 0 is 0 B.1 = B Any value and 1 is itself C.C = C Any value and itself is itself D+0 = D Any value or 0 is itself E + 1 = 1 Any value or 1 is 1