What is Error Handling?
                     What is Error Handling?
Introduction
The tasks of the Error Handling process are to detect each 
error, report it to the user, and then make some recovery 
strategy and implement them to handle the error. During this 
whole process processing time of the program should not be 
slow.
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Functions of Error Handler
● Error Detection
● Error Report
● Error Recovery
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Error Detection
Errors in the program should be detected and reported by the 
parser.  Whenever an error occurs, the parser can handle it and 
continue to parse the rest of the input. 
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Error Detection Cont.
Although the parser is mostly responsible for checking for 
errors, errors may occur at various stages of the compilation 
process.
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Logic errors
Logic errors occur when programs operate incorrectly but do 
not terminate abnormally (or crash). Unexpected or undesired 
outputs or other behaviour may result from a logic error, even if 
it is not immediately recognized as such.
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Run-time  errors
A run-time error is an error that takes place during the 
execution of a program and usually happens because of 
adverse system parameters or invalid input data. The lack of 
sufficient memory to run an application or a memory conflict 
with another program and logical error is an example of this.
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Compile-time  errors
Compile-time errors rise at compile-time, before the execution 
of the program. Syntax error or missing file reference that 
prevents the program from successfully compiling is an 
example of this.
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Classification of Compile-time  errors
1. Lexical : This includes misspellings of identifiers, 
keywords or operators
2. Syntactical : a missing semicolon or unbalanced 
parenthesis
3. Semantical : incompatible value assignment or type 
mismatches between operator and operand
4. Logical : code not reachable, infinite loop.
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Finding error or reporting an error
1. Goal detection of an error as soon as possible without 
further consuming unnecessary input 
2. How: detect an error as soon as the prefix of the input 
does not match a prefix of any string in the language. 
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Error Recovery
The basic requirement for the compiler is to simply stop and 
issue a message, and cease compilation. There are some 
common recovery methods that are as follows. 
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