When developing programSequences of instructions for a computer. there are two types of error (bugAn error in a program.) that often occur:
syntax errorError in a program resulting from code not following syntax rules governing how to write statements in a programming language.
logic errorError in a program which does not cause a program to crash but causes unexpected results.
Syntax errors
A syntax error occurs when code written does not follow the rules of the programming language. Examples include:
misspelling a statement, eg writing pint instead of print
using a variableA memory location within a computer program where values are stored. before it has been declared
missing brackets, eg opening a bracket but not closing it
A program will not run if it has syntax errors. Any such errors must be fixed first. A good integrated development environment (IDE) will usually point out any syntax errors to the programmer.
Logic errors
A logic error is an error in the way a program works. The program simply does not do what it is expected to do.
Logic errors can have many causes, such as:
incorrectly using logical operators, eg expecting a program to stop when the value of a variable reaches 5, but using <5 instead of <=5
incorrectly using Boolean operatorAND, OR and NOT. Used to build complex queries in a database.
unintentionally creating a situation where an infinite loopA loop that repeats forever, ie indefinitely. may occur
incorrectly using brackets in calculations
unintentionally using the same variable name at different points in the program for different purposes
referring to an element in an arrayA set of data values of the same type, stored in a sequence in a computer program. Also known as a list. that falls outside of the scope of the array
Unlike a syntax error, a logic error will not usually stop a program from running. Instead the program will run but not function as expected.
What happens when there is a logic or syntax error in a program?