Computer Systems

Question 1

What is hardware?

Answer 1

Physical components of the computer components (including internal components and external components)

Question 2

What are some examples of hardware?

Answer 2

CPU, motherboard, RAM, ROM, printer, transistors, speakers etc.

Question 3

What is software?

Answer 3

Programs that run on a computer, made up of sequences of instructions that are executed in order to perform a task

Question 4

What are the two main types of software?

Answer 4

1) Application Software
2) System Software

Question 5

What is application software?

Answer 5

Programs that complete a specific task for the user

Question 6

What is system software?

Answer 6

Programs that operate, control and maintain the computer and its components

Ms: controls operation of computer system

Question 7

What are examples of application and system software?

Answer 7

Application Software:
- word processor
- web browser
- image editor
- video editor
System Software:
- operating systems
- utility programs
- libraries
- translators

Question 8

What are the main types of system software?

Answer 8

1) Operating Systems
2) Utility Programs
3) Libraries
4) Translators

Question 9

What are operating systems and why are they used?

Answer 9

Operating systems provide an interface between hardware and applications; provide platform for applications to run on as well as core functionality
- provides virtual machine to manage and control access to computer’s resources
- ms: hides the complexity of the hardware from the user

Question 10

What are utility programs and why are they used? (MS)

Answer 10

Perform system maintenance tasks such as compression, encryption and defragmentation

MS:
Description : (Software that) performs a non-core / ancillary / specific management function for a computer;
Example : Virus checker, disk defragmenter, backup, compression, encryption software etc.

Question 11

What are libraries and why are they used?

Answer 11

Provide reusable code for useful functions that are frequently used by a program;
Reduce amount of programming required for standard features;

Ms:
Provides routines that can be used in code
Increase development speed

Question 12

What are translators? What are the different types of translators?

Answer 12

Translate source code into low-level machine code that can be executed by computer or virtual machine;
- Interpreters, compilers and assemblers

Question 13

What are the roles of an operating system in a computer?

Answer 13

• Hide complexity through virtual machine
• Creates a platform for applications to be written for
• Provide functionality to applications i.e. handle I/O (which forms API)
• Acts as an interface between user or applications and the hardware

Question 14

What are the managers in the operating system?

Answer 14

1) Memory manager - allocate memory to running applications
2) Process manager - controls allocation of CPU cycles
3) Application manager - controls installation
4) File manager - control storage of data on disks
5) Device manager - control interaction with external hardware
6) Security manager - authenticates user
7) Networking manager - provides TCP and UDP sockets

Question 15

What is defragmentation and when is it used and why?

Answer 15

• Arranging data in hard disk memory
• Improve performance
• Not used for SSDs as no moving parts

Question 16

What is machine code?

Answer 16

Programs that are written in binary where the instructions are specific to each processor.

Question 17

What is machine code made of and what does each component do?

Answer 17

1) Operation codes - binary value for a particular instruction
2) Operand - data used in instruction

Question 18

What is assembly language?

Answer 18

Low-level programming language where programs are expressed as mnemonics that are easier to understand and recall

• Assembly language instructions relate to machine code in a 1:1 mapping

Question 19

What are the low-level programming languages and what are key properties of one?

Answer 19

• Assembly language and machine code
• Based on instruction set
• Close to hardware (interacts with basic hardware directly)
• Languages are architecture-dependent and hence are not portable

Question 20

What are high-level programming languages?

Answer 20

• Human-oriented, english like statements
• Use abstraction (many-to-one mapping to machine code instructions)

Question 21

What are the benefits of high-level programming languages?

Answer 21

• Use of English-like statements makes it easier to understand by humans and hence fix errors
• Multiple machine code instructions with a single statement so it is shorter and quicker to write
• Meaningful identifiers, reusable libraries and programming structures
• Data structures
• Portable (not architecture-dependent)

Question 22

What are imperative programming languages?

Answer 22

Provide instructions that are executed by computer in defined sequence in order to complete a process
- machine code and assembly are imperative

Question 23

What are logic gates?

Answer 23

• Components that make up a computer’s processor
• Apply logical operations to boolean inputs for a single output

Question 24

What are the logical gate symbols?

Answer 24

NOT, AND, OR, XOR, NAND, NOR

Question 25

What is the truth table and symbol for a NOT gate?

Answer 25

- indicate NOT with overbar (-- above input)

Question 26

What is the truth table and symbol for a AND gate?

Answer 26

- A . B

Question 27

What is the truth table and symbol for an OR gate?

Answer 27

Question 28

What is the truth table and symbol for an XOR gate?

Answer 28

Question 29

What is the truth table and symbol for a NAND gate?

Answer 29

Question 30

What is the truth table and symbol for a NOR gate?

Answer 30

Question 31

How do we combine logic gates to produce a half-adder circuit?

Answer 31

Question 32

How do we combine logic gates to produce a full-adder circuit?

Answer 32

Question 33

What is an edge-trigged D-type flip-flop?

Answer 33

Memory unit that can be used to store the value of a single bit. Set to the value of data bit every time the clock signal alternates

Question 34

What are compilers and what are they used for?

Answer 34

- Translates a high-level program’s source code in one go, directly to produce object code which is in machine code - object code is an executable file so will not need to be compiled again every time it is run - When the object code is run you do not need the compiler - customer cannot see source code, when program is distributed, so not copied - if an error is detected, compilation fails

Question 35

High level vs low level programming

Answer 35

Question 36

What is the use of a interpreter?

Answer 36

- translates program into machine code line by line, and then executing it - it does this by translating each statement by callings its own subroutines already translated into machine code - if it detects a runtime error the programmer is made aware of the error at that line, and the translation stops - program must be interpreted every time it is executed

Question 37

What is the use of an assembler?

Answer 37

- converts assembly language into machine code - each assembly code statement translate into one machine code statement, so simple instruction

Question 38

Interpreter vs compiler (MS)

Answer 38

- Compiler translates all the code in one go to produce an executable file, interpreter translates and executes one line at a time - Compiled programs execute faster as all code is already in machine code, whereas for interpreter each line is translated before executed - Compilers produce object code so when executed does not not need to be compiled every time, unlike interpreter

Question 39

Describe how bytecode programs are executed after the bytecode has been produced. (MS)

Answer 39

A virtual machine; performs just in time compilation // translation; to convert the bytecode to object code and execute it; // A virtual machine; interprets bytecode an instruction at a time; and runs the necessary code/subroutine to carry out the command in the hardware’s instruction set;

Question 40

Explain why some compilers produce bytecode as the final output instead of executable code. (MS)

Answer 40

The code may need to run on multiple platforms // target platform may not be known // may need to be platform independent;

Question 41

Explain how intermediate language code is used after it has been generated. (MS)

Answer 41

Software must be used to finish the translation process (on the computer running the program); The (JIT compiler) compiles the intermediate language code / bytecode into machine code for the processor / platform / computer it is being executed on; Use a virtual machine // a just-in-time / JIT compiler; (The virtual machine will) interpret / translate / execute the intermediate language code / bytecode // call functions within its own code to carry out the command; Each processor instruction set / architecture will have its own virtual machine;

Question 42

Explain why having a different processors might make it impossible for an executable file to run on a different computer. (MS)

Answer 42

The executable file is platform dependent / machine-specific / using the instruction set of the computer that created it; Different processors may have different instruction sets;

Question 43

Boolean algebra cheatsheet

Answer 43

Question 44

Explain the general purpose of a D-type flip-flop. (MS)

Answer 44

Used to store state (of data input) // used as a memory (unit);

Question 45

Discuss the advantages and disadvantages of programming using a high-level language compared to programming using assembly language. (MS)

Answer 45

Advantages of high-level language (MAX 2): Program code is easier to understand/maintain/debug; Faster development time // programmers can be more productive // one line of HLL code can do the same job as many lines of assembly language; Programs are (more) portable (to other hardware platforms) Availability of flow control structures; A. Example(s) eg loops, selection Improved features for supporting modularity; A. Ability to use subroutines Built-in support for data structures; A. Example(s) eg arrays, records Language is problem-oriented; Support for different paradigms; A. Examples eg functional programming Disadvantages of high-level language (MAX 2): Assembly language code may execute more quickly; R. If response suggests that faster execution is because translation is not required Assembly language code may use less memory; Assembly language gives direct/better access to computer hardware // enables direct manipulation of memory (contents);