3.4 Computer Systems

Question 1

What is hardware ?

Answer 1

Hardware is the physical components which make up a computer

Question 2

What is software ?

Answer 2

Software are the instructions which control the computers physical components

Question 3

What is a general purpose system ?

Answer 3

General purpose systems are computer systems that can perform many tasks and have replaceable software e.g PC or Mac

Question 4

What is an embedded system ?

Answer 4

An embedded system is a computer system built inside of another device to support their operation and have specific firmware burned onto the chips

Question 5

What is application software ?

Answer 5

Application software is software that performs end user tasks

Question 6

What is system software ?

Answer 6

System software are programs which are needed to enable the computer to function e.g OS, utility software

Question 7

What are operating systems ?

Answer 7

Operating systems manage the hardware in a computer and provide an interface for applications to run

Question 8

Why is the operating system needed ?

Answer 8

• provide an interface between users, applications and hardware
• manage memory between running applications and processes
• allocate processor time to different processes/task
• handle input/output devices

Question 9

What are the functions of the operating system

Answer 9

• memory manager
• application manager
• I/O device manager
• security manager
• process manager

Question 10

What is the memory manager ?

Answer 10

The memory manager allocates primary memory (RAM) to the different processes which are running on the computer

Question 11

What is processor management ?

Answer 11

Each cpu core can only process one instruction at a time, therefore when there is multiple applications running, the OS tells the CPU which applications instructions to process at a specific time

Question 12

What is Input/output device management ?

Answer 12

The I/O devices, also called peripherals allow computers to take inputs and give outputs. The I/O device manager allows data to be read and sent to the peripherals. The I/O management is also responsible for the installation of device drivers

Question 13

What is the application manager ?

Answer 13

When a new application is installed the OS will manage this process. The application manager also allocates memory space for the application and controls the applications access to data or devices

Question 14

What is security management ?

Answer 14

The security manager controls which users can access the system, the security manager also prevents users from accessing files and data they shouldn’t have access to. The security manager Also manages the computers firewall ensuring only permitted applications are able to run on the computer.

Question 15

What is utility software and what are some examples ?

Answer 15

utility software is a type of system software that performs specific tasks to help maintain the system, including:

• encryption software
• defragmentation
• data compression
• backup software

Question 16

What is defragmentation software ?

Answer 16

Defragmentation programs, improve hard disks performance by applying an algorithm to reorganise data stored on the disk.

Question 17

What is encryption software ?

Answer 17

Prevents unauthorised users from access to files by applying an algorithm to scramble the data

Question 18

What is backup software ?

Answer 18

Makes copies of data that can be restored in case of data loss

Question 19

What is compression software ?

Answer 19

Compression software applies and algorithm to reduce the space required to store a file and its contents (lossless)

Question 20

What are the differences between high-level and low-level programming languages ?

Answer 20

High-level languages:
- human-readable, easier to develop and debug
- one statement replaces many cpu instructions
- must be translated for the CPU to execute
Low-level languages:
- provides exact control over the cpu
- hard to write by humans
- is specific to one CPU

Question 21

What is the difference between machine code and assembly language ?

Answer 21

• Machine code are instructions stored in binary and are executed by the processor
• assembly language are stored in short mnemonics in place of binary to make it easier to program
  Key point:
• there is 1:1 mapping between machine code and assembly mnemonics

Question 22

What are the purpose of translators ?

Answer 22

• all programs must be translated into machine code before it can be run by any processor

Question 23

What are the 3 types of translators ?

Answer 23

• interpreter, high to low
• compiler, high to low
• assembler, low to low

Question 24

How does a compiler work ?

Answer 24

1) translated high-level program in one go into object code which contains machine code
2) produces an executable file so the original code does not need to be compiled again

Question 25

How does an **interpreter work** ?

Answer 25

1) translates program into machine code, **line by line** and then executing it 2) it does this by translating each statement by calling it’s **subroutines which are already translated into machine code** 3) if it detects a runtime error the programmer is made aware of the error at that line, and the translation stops 4) **source code** needs to be interpreted every time it is run

Question 26

How do **assemblers** work ?

Answer 26

assemblers translate low-level assembly language into machine code **all at once**

Question 27

When would you use **compilers** ?

Answer 27

- production of programs for **commercial distribution** - producing **executable files**, that can be run without any additional software

Question 28

When would you use **interpreters** ?

Answer 28

- good for **rapid program development** since there is no need to recompile after changes - good for programs which need lots of **debugging** and **testing**

Question 29

When would you use **assemblers** ?

Answer 29

- used when **low-level** assembly language has been written for a **specific type** of processor e.g **embedded systems**

Question 30

What is the role of **main memory** ?

Answer 30

The role of main memory: - **stores data** while the program is being executed - each memory address has a **unique address** - data and instruction are **replaced in memory as needed**

Question 31

What is the purpose of the **CPU** ?

Answer 31

The purpose of the **CPU** is to read and execute instructions stored in memory by repeatedly carrying out the **fetch-decode-execute cycle**

Question 32

What components make up the **CPU** ?

Answer 32

- **arithmetic and logic unit** - **registers** - **control unit** - **clock** - **buses**

Question 33

What is the purpose of the **control unit** ?

Answer 33

The control unit contains a **clock** that coordinates activity across the cpu and sets the overall **clock speed** of the cpu

Question 34

What is the purpose of the **Arithmetic logic unit** ?

Answer 34

The ALU performs calculations including **addition and subtractions** and **Boolean comparisons**

Question 35

What are the purpose of **registers** ?

Answer 35

Registers are **very small amounts of memory** in the cpu that are used to hold **specific instructions** that are required by the cpu to perform the fetch-decode-execute cycle

Question 36

What are **buses** ?

Answer 36

These are components which are **connected via a collection of wires** through wich **data and signals** can be **transmitted**

Question 37

What is the **fetch-decode-execute** cycle ?

Answer 37

1) **Fetch** - the next instruction is fetched from main memory to the cpu instruction register 2) **decode** - the instruction is decoded to work out what it is, by control unit 3) **execute** - the instruction is executed (carried out), by ALU or data may be read or written to main memory

Question 38

What are the factors which affect the **CPU performance** ?

Answer 38

- **Clock speed** - the faster the clock speed, the more instructions can be processed in a second - **CPU cores** - multi-core CPU’s can process multiple instructions at the same time, leading to a potential increase in CPU performance **if programs have been optimised to utilise this feature** - **cache memory size** - Cache memory is used to store **frequently used data and instructions**, having more cache memory allows the CPU to **store more** instructions, **reducing the time lost,** increasing cpu performance

Question 39

What are the 2 types of **main memory** ?

Answer 39

- **RAM** - temporarily stores **program instructions and data** while they are being processed by the cpu, RAM is **volatile** so its contents are lost when the computer is switched off. - **ROM** - **permanently** stores program instructions and data but it cannot be written to, it is **non-volatile** so contents are not lost when computer is switched off **both RAM and ROM can be directly accessed by the cpu**

Question 40

What are **registers** and **cache memory** ?

Answer 40

- **registers** are small units of memory that store **specific pieces of data** that are required during the CPU’s fetch-decode-execute - **Cache memory** is extremely fast and cpu use it to store recently fetched instructions so they can be quickly executed

Question 41

What is the difference between **main memory** and **secondary storage** ?

Answer 41

Main memory: - directly accessed by the cpu - **volatile** - RAM stores data and instructions which are **currently in use** Secondary storage: - **non-volatile** not directly accesses by the cpu - **slower than primary memory**, but larger - **used for long-term storage**

Question 42

What is the need for **secondary storage** ?

Answer 42

- **data and software** are **permanently retained** when the computer is turned off, so allows long-term storage.

Question 43

What are the different types of **secondary storage** ?

Answer 43

- **magnetic storage** - Hard disks, magnetic tapes - **flash memory** - Solid state drives, USB memory sticks - **optical storage** - CD’s, DVD, Blu ray

Question 44

How do **Magnetic hard disks** work ?

Answer 44

1) HD’s contain multiple metal discs **platters** which spin at very high speeds 2) the surface of the platters contain many **tiny magnetised regions**, one end represents 0 the other end represents 1 3) each platter is divided into **tracks** and **sectors**, the intersections of which are called **blocks** 4) as the platters **spin**, a magnetic **read/write head is moved** to the correct **block** on the disk where data should be read/written to

Question 45

What are the advantages and disadvantages of **magnetic Hard disks** ?

Answer 45

Advantages: - **large capacity** - **cheap per GB** - **long-lasting and reliable** Disadvantages: - **relatively slow access times** - **has moving parts so wear by susceptible to wear and tear** - **can be noisy**

Question 46

What are the advantages and disadvantages of **solid state drives** ?

Answer 46

Advantages: - **faster access times** - **no moving parts mean they are more robust** - **SDD’s are smaller in size so are better for smaller devices** Disadvantages: - **smaller capacity** - **higher cost per GB**

Question 47

What are the advantages and disadvantages of **Optical storage** ?

Answer 47

Advantages: - **potable** - **relatively cheap per GB** Disadvantages: - **slower access times** than HDD and SSD - **prone to scratches which can damage the surface** and corrupt data

Question 48

What is **cloud storage** ?

Answer 48

**cloud storage** refers to **remote storage**, accessed via the internet, data is actually stored on **magnetic hard disk drives** at remote locations in giant data centres around the world.

Question 49

What are the advantages and disadvantages of **cloud storage** ?

Answer 49

Advantages: - **files are automatically backed up** - **remote access to files from anywhere** - **enables file sharing** Disadvantages: - **security of data is handled by a third party** - **need an internet connection to access data** - **may need to pay a subscription**

Question 50

What are the advantages of **high-level programming languages** ?

Answer 50

- high-level languages have built-in functions - high-level languages have built-in libraries - high-level languages usually require fewer lines of code to be written - it is easier to find mistakes in the code - it is easier to maintain and debug - it is quicker to develop in high-level