programming languages

Question 1

What is system software?

Answer 1

Needed by the computer to keep the system running

performs the tasks needed to operate the hardware

Question 2

What is application software?

Answer 2

Useful for the user, allows them to perform tasks such as writing a letter

Question 3

Give three examples of system software

Answer 3

operating system
library programs
utility programs

Question 4

Give the three types of application software

Answer 4

general purpose
special purpose
bespoke software

Question 5

What does the operating system do?

Answer 5

Acts as an interface between user and hardware, provides a ‘virtual machine’
eg by displaying files as distinct sections which can be dragged etc

Question 6

What are library programs?

Answer 6

Pre-compiled routines for re-use

Question 7

Give three examples of utility programs

Answer 7

disk formatter, file compressor, firewall etc

Question 8

Give two examples of general purpose application software

Answer 8

word processor, spreadsheet

Question 9

Give two examples of special purpose application software

Answer 9

payroll, tax calculator, (web browser)

Question 10

What is bespoke application software?

give two examples

Answer 10

Software which has to be specially written for a specific purpose, it cannot just be bought off the shelf
eg London congestion simulator, air traffic control

Question 11

What is machine code?

Answer 11

instructions which a computer can respond to directly without having to translate

Question 12

What are the disadvantages of machine code?

Answer 12

• slow and tedious to write
• Hard to debug
• Machine specific, every type of computer has a different set of instructions

Question 13

What is assembly language?

Answer 13

Still machine specific but had mnemonics (more meaningful abbreviations for instructions) and comments, labels and variables. Must be translated back to machine code before use.

Question 14

When was assembly code developed?

Answer 14

The 1950s

Question 15

When were high level languages developed?

Answer 15

The late 1950s

Question 16

Name two of the first high level languages

Answer 16

FORTRAN and COBOL

Question 17

What is the difference between high level languages and assembly and machine code?

Answer 17

• High level languages are problem centred, independent of different hardware platforms
• One line of high level language can correspond to lots of lines of machine code instructions, the lower levels have a one to one relationship

Question 18

What are the advantages of high level languages?

Answer 18

• Easier to read, write and debug
• More like a natural language, usually based on syntax similar to English
• Not machine specific

Question 19

What are the disadvantages of high level languages?

Answer 19

Needs to be translated much more than the others as one line of code can be much more than one line of machine code

Question 20

What are the different types of high level languages known as?

Answer 20

programming paradigms

Question 21

What are the two kinds of programming paradigm?

Answer 21

imperative/procedural and declarative

Question 22

What is an imperative/procedural language?

Answer 22

A list of commands to be executed in sequence

Question 23

Give two examples of an imperative/procedural language

Answer 23

• pascal

- C

Question 24

What is a declarative language?

Answer 24

A program which defines rules and goals without specifying a precise flow of control, often used for AI

Question 25

Give three examples of declarative languages

Answer 25

LISP, prolog, SQL

Question 26

Give the generations of programming language in order

Answer 26

1=machine code
2=assembly language
3=high level languages
4=declarative languages

Question 27

Why might assembly code still be used?

Answer 27

• You have more complete control over the hardware
• more efficient as program will run faster
• uses less memory
• useful for low level software or for writing compilers for higher level languages

Question 28

What is a compiler?

Answer 28

an automatic machine code translator for high level languages

Question 29

What are the two kinds of translator?

Answer 29

• assembler

- compiler/interpreter

Question 30

What is an assembler?

Answer 30

Translates assembly code to machine code

The relationship is one to one so the translation process is quite simple

Question 31

What do compilers/interpreters do?

Answer 31

Translate high level languages to machine code

Question 32

What is the difference between an compiler and a interpreter?

Answer 32

• compilers takes the source code and translates and saves it as an executable file (which can then be re-used without further translation)
• interpreters translate the source code one line at a time, executing it immediately(no machine code version is saved)

Question 33

What are the advantages of compilers?

Answer 33

• Better if you need to run source code repeatedly(including running loops inn the program)-faster because it doesn’t have to be translated repeatedly
• A user doesn’t have to have any translation software to run an executable file
• A user cannot see the source code from an exe file, protecting intellectual property

Question 34

What are the advantages of interpreters?

Answer 34

• Easier to write than compilers

- Use fewer resources

Question 35

What is the role of interpreters in the internet?

Answer 35

most webpages contain javascript sent as plain text and web browsers have javascript interpreters
Every computer accessing the web page (with different operating systems) can interpret the code itself for the relevant operating system

Question 36

Why do webpages not send script as an executable file?

Answer 36

exe files are platform specific, so would not work on all computers accessing the page

Question 37

What are hybrid/two-stage models?

Answer 37

Some modern languages (eg java) translate in two stages, using compilation and interpretation

Question 38

How does hybrid/ two stage translation work?

Answer 38

• The source code is translated to bytecode, a platform independent intermediate stage
• By run time the byte code is compiled or interpreted to machine code

Question 39

What are the advantages of byte code?

Answer 39

• It can be distributed regardless of operating system
• copyright is protected
• It is the same whatever the original language was

Question 40

What are the disadvantages of byte code?

Answer 40

Software (eg java) has to be installed to interpret the byte code

Question 41

What is software?

Answer 41

consists of sequences of instruction which can be understood and executed by hardware

Question 42

What is the column on the left when machine code is written?

Answer 42

The memory adress