Pascal Programming: Week 4 Notes       


More on Robust Input 
Allow for varied user input to general questions:
Solution to: "Y" or "y" or "Yes" or "yes" or "1"
       			Sets - Using the "IN" operator
			List of values in a set
			Expression preceding In must be a String or Integer
No Real
Boolean makes no sense
			use of "NOT" with "IN" operator
		Example:
			Ans in ['Y', 'y', 'Yes', 'yes']


More on Evaluating Expressions
	Boolean Truth Tables
	The Difference between CAND/COR and AND/OR
	Short-Circuit vs. Complete Evaluation
	Problems and Reasons (Speed versus Logic)

	Example:
			IF (Value <> 0) AND (Answer DIV Value >= 20) THEN
				Writeln(' Incorrect');
		Fix:
 			IF (Value <> 0) THEN
			     IF (Answer DIV Value >= 20) THEN
				Writeln(' Incorrect');

	Compiler Directives
		Global and Local
		{$B+}  {$B-}


The Use of Flags
	Purpose: to provide a checking mechanism.
		If some condition is met the flag is set to a particular value.
		Differing actions are taken depending upon the value of the flag.
	Real-time Equivlent


Branching and Looping: Branching
	The differences are seen in Assignment #2
IF THEN <do this>	vs.	IF  <this> THEN IF  <this> THEN  <do this>
Two-way branching and Multi-way Branching 
	Binary Tree vs. Graph Structure
	IF THEN
		ELSE IF
		ELSE IF
		ELSE …
Another Method:
CASE Statements
Examples:
	PROGRAM CaseSample (input, output);
	VAR
	     Grade: char;
	BEGIN
	      Writeln('What grade did you get?');
	       Readln(Grade);

	       CASE Grade of
		'A', 'B': Writeln('Great');
		'C':	Writeln('OK');
		'D', F':	Writeln('Give up');
	       ELSE	Writeln('Not a Valid Grade');
	       END;  {Case Statement}

	       Writeln('See ya later!');
	       Readln;
	END.


Branching and Looping: Looping
	WHILEs and REPEATs
	Another Method:
		FOR Loops
	Examples:

		FOR i:= 1 to 20 Do
		     BEGIN
			{Do Something}
			i:= i+1;
		     END;

		Beginning:= 1; Ending:= 20;
		FOR i:= Beginning to Ending Do
		     BEGIN
			{Do Something}
			i:= i+1;
		     END;

Often used in indexing through arrays.


Functions
	Pre-defined:  SQR(), SQRT(), TRUNC(), ROUND(), and others
	User-defined: CUBE() example
		Functions are expressions 
		Written like a function but it returns a value


Arrays
	One-Dimensional Array Declaration
	Usage of arrays


User-Defined Types
	Overview of Type Declaration
	Example