WJEC 1.8 Program Construction

A syntax error is...

• An error in the grammar of how you have written your code such as a spelling mistake

• An error which causes the program to crash when it runs, such as dividing by zero or running out of memory

• An error which doesn't stop the program from running but makes it give you the wrong answer such as using the wrong sign

• An error where you have accidentally rounded a number up

• An error where you have accidentally lost the decimal part of a number

A runtime/execution error is...

• An error in how you have written your code such as a spelling mistake

• An error which causes the program to crash when it runs, such as dividing by zero or running out of memory

• An error which doesn't stop the program from running but makes it give you the wrong answer such as using the wrong sign

• An error where you have accidentally rounded a number up

• An error where you have accidentally lost the decimal part of a number

A logic error is...

• An error in how you have written your code such as a spelling mistake

• An error which causes the program to crash when it runs, such as dividing by zero or running out of memory

• An error which doesn't stop the program from running but makes it give you the wrong answer such as using the wrong sign

• An error where you have accidentally rounded a number up

• An error where you have accidentally lost the decimal part of a number

What type of error is this?

• Logical

• Runtime/Execute

• Syntax

• Rounding

• Truncation

The program is checked to ensure it conforms to the syntax rules for that language e.g. an error would appear if a semi-colon was missing

• Lexical analysis

• Syntax analysis

• Semantic analysis

• Code generation

Variables are checked that they are used properly and the that operations such as (+ - / and *) have been correctly used at this stage

• Lexical analysis

• Syntax analysis

• Semantic analysis

• Code generation

Semantic analysis is?

• Comments and unneeded spaces are removed. Remaining code is turned in to tokend and. A symbol table is created which holds the addresses of variables, labels and subroutines.

• Tokens are checked to see if they match the spelling and grammar expected. This is done by parsing each token to determine if it uses the correct syntax for the programming language. If syntax errors are found, error messages are produced.

• Variables are checked to ensure that they have been properly declared, used and are the correct data type. Operations are checked to ensure that they are legal for the type of variable being used, e.g. you would not try to store the result of a division operation as an integer.

• Machine code is generated. Code optimisation to run as fast as possible. redundant data is removed.

Syntax Analysis is?

• Comments and unneeded spaces are removed. Remaining code is turned in to tokend and. A symbol table is created which holds the addresses of variables, labels and subroutines.

• Tokens are checked to see if they match the spelling and grammar expected. This is done by parsing each token to determine if it uses the correct syntax for the programming language. If syntax errors are found, error messages are produced.

• Variables are checked to ensure that they have been properly declared, used and are the correct data type. Operations are checked to ensure that they are legal for the type of variable being used, e.g. you would not try to store the result of a division operation as an integer.

• Machine code is generated. Code optimisation to run as fast as possible. redundant data is removed.

Lexical Analysis is?

• Comments and unneeded spaces are removed. Remaining code is turned in to tokend and. A symbol table is created which holds the addresses of variables, labels and subroutines.

• Tokens are checked to see if they match the spelling and grammar expected. This is done by parsing each token to determine if it uses the correct syntax for the programming language. If syntax errors are found, error messages are produced.

• Variables are checked to ensure that they have been properly declared, used and are the correct data type. Operations are checked to ensure that they are legal for the type of variable being used, e.g. you would not try to store the result of a division operation as an integer.

• Machine code is generated. Code optimisation to run as fast as possible. redundant data is removed.

Translates low level assembly language mnemonic into machine code

• Assembler

• Compiler

• Interpreter