Computer Systems

Question 1

What is hardware?

Answer 1

Physical and electrical components of a computer

Question 2

What is software?

Answer 2

Programs that run on the computer, made up of sequences and instructions.

Question 3

What are the two main types of software?

Answer 3

• Application software
• System software

Question 4

What are the different types of system software?

Answer 4

• Operating system
• Utility programs
• Libraries
• Translators

Question 5

What is the role of the operating system?

Answer 5

Hide the complexity of the computer’s hardware through the use of a virtual machine.

Question 6

What is a virtual machine?

Answer 6

A model that creates the illusion that each process has all of the machines processing power to itself.

Question 7

What are the main functions of the operating system?

Answer 7

• Memory Manager
• Process Manager
• Application Manager
• File Manager
• Device Manager
• Security Manager
• Networking Manager

Question 8

Describe memory management

Answer 8

Controls which areas of memory are allocated to running processes/applications

Question 9

Describe process management

Answer 9

Controls the allocation of CPU cycles to multiple running applications. More demanding processes are provided more processing resources as well as those which the OS deems of a higher priority.

Question 10

Describe File Management

Answer 10

Controls the storage of data on physical disks as files and manages their read/write/execute permissions.

Question 11

Describe device management

Answer 11

Controls interactions with existing hardware devices and handles the installation of device drivers. This is required as each device is designed differently and prevents the programmer from having to know exactly how each one works.

Question 12

Describe security management

Answer 12

Authenticates users of the computer and controls access to features and files based on user access levels

Question 13

Describe network management

Answer 13

Provides TCP and UDP sockets for networked applications, handles WiFI connection and manages the computer’s IP address.

Question 14

What are utility programs?

Answer 14

They allow users to perform system mainantance tasks such as encryption, scanning for viruses, defragmentation and backing up.

Question 15

What are libraries?

Answer 15

Provide reusable code that software applications require in order to run. Their use can reduce the amount of programming required as they provide access to standard features.

Question 16

What are translators?

Answer 16

Translate higher-level programming code into low-level machine code

Question 17

What are the OR Boolean Algebra identities?

Answer 17

• A + 0 = A
• A + 1 = 1
• A + A = A
• A + Ā = 1

Question 18

What are the AND Boolean Algebra identities?

Answer 18

• A . 0 = 0
• A . 1 = A
• A . A = A
• A . Ā = 0

Question 19

What is the NOT Boolean Algebra identity?

Answer 19

Not Ā = A

Question 20

What is the XOR Boolean Algebra identity?

Answer 20

(A . B’) + (Ā . B) = A ⊕ B

Question 21

What is opcode?

Answer 21

The binary value associated with a particular instruction

Question 22

What is an operand?

Answer 22

The data used by the instruction / opcode

Question 23

What is an imperative language?

Answer 23

Provide instructions that are executed by the computer in a defined sequence in order to solve the problem

Question 24

What does machine code consist of?

Answer 24

• Opcodes
• Operands

Question 25

What is the relationship between assembly and machine code?

Answer 25

One assembly instruction relates to one machine code instruction in a 1:1 mapping

Question 26

What are the advantages of low-level programming languages?

Answer 26

- Direct control over the hardware - Results in smaller object code making it suitable for embedded systems with limited memory - Fast execution speed as the code is written specifically for the hardware and can take advantage of its capabilities

Question 27

What are the disadvantages of low-level languages?

Answer 27

- Difficult to understand and easy to make mistakes - Difficult to trace and identify errors - Time consuming to develop software - No built-in functions - Not portable

Question 28

What are the characteristics of low-level languages?

Answer 28

Instruction made up of opcodes and operands, expressed in binary or mnemonics

Question 29

What are the characteristics of high-level languages?

Answer 29

- Human-oriented, English-like instructions and statements - One statement represents several low-level languages

Question 30

What’s are the advantages of high-level languages?

Answer 30

- Can use meaningful identifiers, subroutines, selection, iteration, data structures - Easier to understand the logic and structure of the program; easier to debug - Maintain one source code that can be used across multiple architectures - Built in libraries and additional functionalities - Portable

Question 31

What are the disadvantages of high-level languages?

Answer 31

- Lack of direct control over the hardware - Execution generally slower than low-level languages as translated machine code is general rather than tailored to the specific machine - Object code is larger

Question 32

What is object code?

Answer 32

Program that contains the binary machine code for the computer’s instruction set

Question 33

What are the three different types of translators?

Answer 33

- Assemblers - Compilers - Interpreters

Question 34

What is an assembler?

Answer 34

Translates assembly source code into machine code.

Question 35

What are compilers?

Answer 35

- Produce object code that can be executed in a specific machine architecture - All of the programs source code is translated in one go before the program is run

Question 36

What are the advantages of compilers and compiled languages?

Answer 36

- Compiled code executes more quickly - No further software is required to run the executable program - Once compiled, source code is not required protecting the developer’s intellectual property - Compiled code is difficult to reverse engineer

Question 37

What are the disadvantages of compilers and complied languages?

Answer 37

- Can only be executed on a machine with a particular instruction set for the object code - Compiling a program can take a long time

Question 38

What are interpreters?

Answer 38

No object code is produced, instead programs are translated into machine code instructions line-by-line as the program is executed

Question 39

What are the advantages of interpreters and interpreted languages?

Answer 39

- More portable as it will run on any host computer with the appropriate interpreter installed - Errors are easy to track down as the program will stop when one is encountered - Program runs immediately

Question 40

What are the disadvantages of interpreters and interpreted languages?

Answer 40

- Executed more slowly as each line needs to be installed on the go - Host computer must have the appropriate interpreter installed - Source code must be made available in order to run the program

Question 41

When would you use a compiler?

Answer 41

- produce an executable binary program file - needs to be run quickly or host has limited memory - protect developer’s intellectual property

Question 42

When would you use an interpreter?

Answer 42

- prototyping and testing code - needs to be run on a wide range of processor architectures

Question 43

What is bytecode?

Answer 43

An intermediate code executed by a virtual machine provided by a runtime environment that performs just-in-time compilation and execution of bytecode or interprets bytecode using pre-compiled subroutines.

Question 44

Why is bytecode used?

Answer 44

- Portable: only if the virtual machine is available on the host computer - Executed faster than fully interpreted languages: not as fast as natively compiled code - Consists of opcodes and operands so no need to distribute source code - Applications need to be run on a different processor architecture