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Published byPhilomena Griffin Modified over 9 years ago
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So now we’re programming
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What do programs do? Manipulate (process) data Math Read files Write to files Create files
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Good programmers Always Always start with pseudocode See page100
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Programs must be named You choose the name It must be one word follow with a semi-colon Example: Program First_Program ;
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Next, type program comments Program First_Program; (***********************************) (* Program: First.pas *) (* Programmer: Sue Halfhill *) (* Date: September, 1999 *) (* Description: Program is a point of sale *) (* system *) (***********************************)
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Next, declare any constants Constants do not change value Program First_Program; (***********************************) (* Program: First.pas *) (* Programmer: Sue Halfhill *) (* Date: September, 1999 *) (* Description: Program is a point of sale *) (* system *) (***********************************) CONST Multiplier = 5;
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Next, declare any variables Program First_Program; (***********************************) (* Program: First.pas *) (* Programmer: Sue Halfhill *) (* Date: September, 1999 *) (* Description: Program is a point of sale *) (* system *) (***********************************) VAR Fname : String[15]; Lname : String[25]; Sum, X, Y : Integer;
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String Variables Contain alpha-numeric data Are 256 bytes in size unless declared –Use [ ] to declare smaller size
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Char One byte only in size Byte Either True or False
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Integers vs Real Whole numbers Legal values of - 32,768 to 32,767 Use LongInt for larger numbers +, -, *, div, MOD Must have decimals Can be used for exponents Maximum value determined by computer memory +, -, *, /
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Integer vs Real Real Integer
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Implications Integers variables can be assigned to Real Variables Real variables can not be assigned to Integer variables
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Next Code must start with Begin and finish with End. Program First_Program; (***********************************) (* Program: First.pas *) (* Programmer: Sue Halfhill *) (* Date: September, 1999 *) (* Description: Program is a point of sale *) (* system *) (***********************************) VAR Fname : String[15]; Lname : String[25]; Sum, X, Y : Integer; Begin ====== End.
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Putting values into variables Sum := 2 + 4; FName := ‘John’; Variable Name Assignment Operator Literal or Value being stored
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Assigning Values Program First_Time; CONST Multiplier = 5; VAR Fname : String[15]; Lname : String[25]; Sum, Sum, X, Y : Integer; Begin X := 2; Y := 6; Sum := Multiplier(X + Y); Writeln(Sum); End;
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How ‘Hard Code’ User Input Read from a file OH- OH
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Read Procedure Read(parameter,parameter) Readln(parameter,pararmeter) Reading numeric data vs string data
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Read(parameter,parameter) 7 5 Read(A,B) Space is a delimiter (separator) for integer or real data 7 5 With the read procedure the marker does not go to the next line
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Readln(parameter,parameter) 7 5 Readln(A, B) 7 5 8 40 With the readln procedure the marker goes to the next line
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String Variables vs Read/Readln The size of A and B determine how much is read Dataline : string[9] reads up to 9 characters (letters, spaces, numbers, etc)
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Write/Writeln Cursor similar to Read/Readln; Directs data to –screen Writeln(‘What is your name’); –to file Writeln(filename, Sum); –to printer Writeln(lst, ‘What is your name?’);
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What’s A Function Black Box Command Result X := Length(Data_line) ;
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String Functions
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Begin Writeln(‘Please enter your social security number.’) Read(SSNumber); Writeln(‘Please enter your first name and last name.’) Readln(Data_line); X := Length(Data_line); Y := POS(Blank,Data_line); First_Name := COPY(Data_Line,1,y-1); Delete(Data_Line,1,y); X := Length(Data_Line); Last_Name := Data_line; End.
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X := Length(Data_line) ; Y := POS(Blank, Data_line) ; First_Name := COPY(Data_line, 1, 5) ; Delete(Data_line, 1, y) ;
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X := Length(Data_line); Anatomy of a Function Function Name Parameters Variable which holds value
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X := Length(Data_line) ; Sue Halfhill Data_Line X = 12
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Y := POS(Blank, Data_line) ; Sue Halfhill Blank Y = 4 2 parameters !!!!
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First_Name := COPY(Data_line, 1, 3) ; First_Name Sue Halfhill Data_line } 3 1 Sue 3 parameters !!!!
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Delete Delete(Data_line,1,y)
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Math Functions Round Trunc Sqr Sqrt Str
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STR(X,S) X is an integer or real value X must be formatted. X:4:2 S is a string variable.
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