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Table of Contents
2. TMT Pascal Language Description
2.2. Pascal Language Structure
2.2.12. Procedures and Functions
2.2.12. Procedures and
Functions
Procedures are a sequence of instructions that are separate from the main
code block. Functions are procedures that return a value. Other than this
difference, both procedures and functions are the same.
Procedures are blocks of code that are called from one or more places
throughout your program. Procedures make source code more readable and reduce
the size of the executable because repetitive blocks of code are replaced
with a call to a procedure. Both procedures and functions accept parameters.
Parameters allow the calling routine to communicate with a procedure.
Parameters can be passed by value or by reference or by constant reference.
If passed by value, only the value of the parameter is passed and the procedure
has no access to the actual variable. One can modify the value parameter.
It will have an effect only inside of the procedure body and will not change
the actual variable.
If passed by reference, also known as var parameters, an address of
the memory location containing the value is passed thus making it possible
to modify the variable.
If passed by constant reference, also known as const parameters,
an address of the memory location containing the value is passed but the
compiler does not allow one to modify a constant parameter and does not
allow passing one as an actual variable parameter to another procedure
or function.
Procedures and Functions Declaration
Forward Declaration
External Declaration
Interrupt Procedure
Procedural Value
Using Statement as Procedure
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