Chapter 8 Overheads

FUNCTIONS

A FUNCTION IS A SUBPROGRAM WHICH SENDS BACK ONE ANSWER.
THIS ANSWER IS SENT BACK IN THE NAME OF THE FUNCTION.
THE FUNCTION ITSELF MUST HAVE A TYPE.

LOOK AT THE PROBLEM FROM CHAPTER 6 AGAIN

PRINT OUT A LIST OF THE SOCIAL SECURITY NUMBERS AND LETTER GRADES WHERE THE LETTER GRADES WERE BASED ON THE AVERAGE OF THE SIX TEST GRADES.

VERSION TWO:

READ(SSNO);
WHILE NOT EOF DO
	BEGIN
		GETLETGRADE(AVERAGE,LETGRADE); WRITELN(SSNO,LETGRADE); READ(SSNO);
	END


FUNCTION AVERAGE : INTEGER;

CONST


NOGRADES = 6;

FUNCTION SUM : INTEGER;

VAR GRADE, COUNT, TSUM : INTEGER;

BEGIN



    TSUM := 0;

    COUNT := 0;

    REPEAT





    READ(GRADE);

    TSUM := TSUM + GRADE;

    COUNT := COUNT + 1;




    UNTIL COUNT = NOGRADES;

    SUM := TSUM;


END;

BEGIN



    AVERAGE := SUM DIV NOGRADES;


END;

VERSION THREE:

READ(SSNO); WHILE NOT EOF DO
	BEGIN
		WRITELN( SSNO, LETGRADE( AVERAGE ) ); READ(SSNO);
	END;

AND PROCEDURE GETLETGRADE BECOMES

FUNCTION LETGRADE( NUMGRADE : INTEGER ) : CHAR;

THE BODY OF THE FUNCTION IS EXACTLY LIKE THE PROCEDURE GETLETGRADE

SUMMARIZE

	TWO KINDS OF SUBPROGRAMS:
	FUNCTIONS
		SEND BACK A VALUE HAVE TYPE PARAMETERS SHOULD ALL BE VALUE PARAMETERS
	PROCEDURES
		MORE GENERAL PURPOSE MAY HAVE NONE, ONE, OR MORE VALUES TO SEND BACK TO CALLING PROGRAM

SOMETHINGS YOU KNOW BUT DON'T KNOW YOU KNOW

	PASCAL HAS SOME BUILT-IN FUNCTION AND PROCEDURES
		EOF is a boolean function READ, READLN are procedures WRITE, WRITELN are procedures

RECAP SUMMARY

PROBLEM
	GENERAL SOLUTION
		TOP DOWN DESIGN
	SPECIFIC SOLUTION
		PASCAL PROGRAM
PASCAL
	CONST, VAR, INTEGER, CHAR WHILE, IF-THEN, IF-THEN-ELSE, REPEAT-UNTIL PROCEDURE, FUNCTION BEGIN, END

	`TSUM := 0; COUNT := 0; REPEAT`
		`READ(GRADE); TSUM := TSUM + GRADE; COUNT := COUNT + 1;`
	`UNTIL COUNT = NOGRADES; SUM := TSUM;`