Software Develoment

Question 1

What are some tools that an integrated development environment might have?

Answer 1

editors
runtime environments
automatic line numbering
error diagnosis
colour coding
debugger
trace
break points
variable watch
auto-correct
auto-suggestion
auto-indent
linker
loader
compiler
interpreters

Question 2

What are some brands of IDE?

Answer 2

Python comes with a simple IDE called IDLE.

Eclipse and Netbeans are two fully featured IDEs used for programming in Java, JavaScript and HTML.

Visual Studio is an IDE that supports several programming languages including Visual Basic.NET and C#.

Question 3

What is an editor program?
Examples of usage

Answer 3

Editors are software that allow programmers to write and edit code.

automatic line numbering
colour coding
auto-correct
auto-suggestion
auto-indent

Question 4

What is a debugging tool?

Answer 4

Debugging tools help programmers to locate and fix errors.

Question 5

What is a break point?

Answer 5

enable a program to be paused or stopped at predetermined points.

Question 6

What is a variable watch?

Answer 6

see the changing values of variables as the program runs.

Question 7

What is error tracing?

Answer 7

Some IDEs pinpoint exactly where a syntax error occurs, or at which line in a program an error is generated.

Tracing involves recording information as a program runs to see how different elements of the program are affected as it progresses.

Question 8

What is a translator?

Answer 8

It’s a program that converts source code into object code.

Question 9

Re-understanding source code for translators

Answer 9

Any program written in a high-level language is known as source code.

However, computers cannot understand source code. Before it can be run, source code must first be translated into a form which a computer understands - this form is called object code.

Question 10

What are the three types translators?

Answer 10

Compilers.
Interpreters.
Assemblers.

Question 11

What is a compiler?

Answer 11

A compiler takes the source code as a whole and translates it into object code all in one go. Once converted, the object code can be run at any time. This process is called compilation.

All of the object files used in a program must be combined before the program can be run.

Question 12

What are some advantages to compilers?

Answer 12

Compiled programs run quickly since they have already been translated.

A compiled program can be supplied as an executable file.

Compilers optimise code. Optimised code can run quicker and take up less memory space.

Question 13

What are some disadvantages to compilers?

Answer 13

there must be enough memory space to hold the source code, the compiler and the generated object code.

Compilers do not usually spot errors - the program has to be compiled and run before errors are encountered

The source code must be recompiled every time the programmer changes the program.

Source code compiled on one platform will not run on another - the object code is specific to the processor’s architecture.

Question 14

What is an interpreter?

Answer 14

An interpreter translates source code into object code one instruction at a time.

It is similar to a human translator translating what a person says into another language, sentence by sentence.

The resulting object code is then executed immediately. The process is called interpretation.

Question 15

What are some advantages to interpreters?

Answer 15

Instructions are executed as soon as they are translated.

interpreters require less available memory.

Errors can be spotted quickly.

Question 16

What are some disadvantages to interpreters?

Answer 16

Interpreted programs run more slowly. The processor has to wait for each instruction to be translated before it can be executed.

Additionally, the program has to be translated every time it is run.

Interpreters do not produce an executable file that can be distributed.

Interpreters do not optimise code - the translated code is executed as it is.

Question 17

What is an assembler?

Answer 17

The purpose of an assembler is to translate assembly language into object code.

Whereas compilers and interpreters generate many machine code instructions for each high-level instruction, assemblers create one machine code instruction for each assembly instruction.

Question 18

What is a loader?

Answer 18

A loader is a piece of software that is responsible for loading executable files into memory to enable the central processing unit (CPU) to run them.

It calculates the size of a program and dedicates enough memory space for it to run efficiently.

Question 19

What a the 6 stages of compilation?

Answer 19

lexical analysis
symbol table construction
syntax analysis
semantic analysis
code generation
optimisation

Question 20

What is lexical analysis?

Answer 20

Comments and unnecessary spaces are removed.

Keywords, constants and identifiers are replaced by ‘tokens’, which are symbolic strings to identify what the elements are.

Question 21

What is symbol table construction?

Answer 21

A table stores the names and addresses of all variables,constants and arrays.

Variables are checked to make sure they have been declared and to determine the data types used.

Question 22

What is syntax analysis?

Answer 22

Tokens are checked to see if they match the syntax of the programming language.

If syntax errors are found, error messages are produced.

Question 23

What is semantic analysis?

Answer 23

Variables are checked to make sure they have been correctly declared and contain the correct data type.

Operations are checked to ensure that they are appropriate for the type of variable being used.

Question 24

What is code generation?

Answer 24

Machine code is generated in this stage.

Question 25

What is optimisation?

Answer 25

makes the program more efficient so it runs faster and uses fewer resources.

Question 26

What are some programming errors?

Answer 26

syntax
runtime/execution
logical
linking
rounding
truncation

Question 27

What is a syntax error?

Answer 27

is an error in the rules of a sequence of characters that have been written in a particular programming language.

Question 28

What is a runtime/execution error?

Answer 28

These are errors that occur only during the execution of a program.

Errors include running out of memory.

Question 29

What is a logical error?

Answer 29

These occur when the program is running, specifically when there is a problem with the logic.

This might be using the < symbol instead of the > symbol, or using AND instead of OR.

Logical errors might not cause an error message or stop a program from running, so they can be hard to find.

Question 30

What is a linking error?

Answer 30

A linking error occurs when a function or library that is needed by the program cannot be found.

This might be because it has not been imported or because a file has been moved.

Question 31

What is a rounding error?

Answer 31

A rounding error is the difference between the number that is stored by a computer program and the actual number.

Data types are often limited in the number of decimal places that they can store so a rounding error might occur if a number needs to be cut short.

An example of this is pi (π) being limited to 3.14 when it is rounded to two decimal places.

Question 32

What is a truncation error?

Answer 32

when a large number is reduced to fit a data type.

The difference between rounding and truncation is that truncation cuts off the extra
decimal places without changing the final digit.

For example, 5.369 rounded to two decimal places is 5.37, but when truncated to two decimal places it is 5.36.