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Computer Science II

Computer Science II. More with files. Goals for today. Review file commands from last class. Be able to read a program that uses files Be able to fix a program that uses files Be able to write a program that uses files and checks if the file exists. Dry run the following

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Computer Science II

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  1. Computer Science II More with files.

  2. Goals for today • Review file commands from last class. • Be able to read a program that uses files • Be able to fix a program that uses files • Be able to write a program that uses files and checks if the file exists.

  3. Dry run the following program fileOfStuff; {5 pts} type RecordType= record a,b:integer; c:real; end; filetype = file of Recordtype; var Shuttle:Recordtype; fyle:filetype; count:integer; begin assign(fyle,'stuff.dta'); rewrite(fyle); for count:= 10 to 13 do begin Shuttle.a:= count DIV 2; Shuttle.b:= count mod 3; Shuttle.c:= (shuttle.a+shuttle.b)/2; write(fyle,shuttle); end; close(fyle); reset(fyle); while not eof(fyle) do begin read(fyle, shuttle); if shuttle.a mod 2 = 0 then writeln(shuttle.a:5, shuttle.b:5, shuttle.c:6:2); end; close(fyle); readln; End. Dry run the following code

  4. Fix File program fix'n-on-Use'n-afile; {This program is to create a file of 10 random numbers (1-50) Then show the elements from the file and count HOW MANY numbers are below the average of the numbers in the file} typo file = phile with integers; var fyle : file; count, belowAve,shuttle, total:integer; ave:real; begin assign(file, 'numb.skl'); reset(numb.skl); for count:= 1 to 10 shuttle = randomize(50) + 1; total = total + shuttle; writeln(file, shuttle); ave:= total/count; close(file) reopen(file); while eof(file) do begin read(file, shuttle); write(shuttle:4); if shuttle > ave then writeln(shuttle) end; writeln; reclose(file); writeln('The number of scores below the average is ', total); close(program) Fixfilebelowave.pason the class website

  5. Declare Assign(Numfile, ‘stuff.dta’); Rewrite(Numfile); Write(Numfile, variable); Close(Numfile); Reset(Numfile); Eof(filename) FileSize(Filename) Seek(Filename,Position); Read(Numfile,Variable); Close(Numfile); Type Filetype = file of integer; Var Numfile:Filetype; Ties the file variable to the file on the disk. Creates (erases) a file to be written to. Puts information into a file. Puts an EOF marker in the file if adding to the file, and releases the file pointer. Opens a pre-existing file Checks for the end of the file Returns the number of ‘chunks’ in the file. Moves the file pointer to the ‘Position’ spot on the file Used to copy information from a file. See above. File review

  6. To do today and Friday • Using what you have learned about files, write a program with the following… • Menu • Create a new file • Check to see if it exists before this • Show all the names from the file • Check to see if it exists • Find if a name is in the file • Check • (Push) Add to an existing file. • Check • Quit • Push: Let the user pick the file name. • Push: Make a file of records to store the name and phone number • Push: Sort the information in the file.

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